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Students should previously have studied
the star patterns in the night sky and the changes in those patterns
with the seasons and lunar cycles. They should also have been introduced
to the solar system; and they can be expected to know that the Sun, which is composed
primarily of hydrogen and helium, is the center of the solar system.
They should also know that the solar system includes Earth and
eight other planets, their moons, and a large number of comets
and asteroids and that gravitational interaction with the Sun primarily
determines the orbits of all these objects. In the eighth grade
students should have learned about the composition, relative sizes,
positions, and motions of objects in the solar system.
Students should become familiar with evidence that dates
Earth at 4.6 billion years old, and they should know that extraterrestrial
objects hit the planet occasion-ally and that such impacts were more
frequent in the past. They have also learned that the Moon, planets,
and comets shine by reflected light. To
study this standard set, students will need to understand electromagnetism
and gravity. Students should know and understand the Doppler effect
and the inverse square law of light (see Standard 4.f in the physics
section of this chapter). Familiarity with the acquisition and analysis
of spectral data will also be helpful. The
content in this standard set may cause students difficulty in grasping
the vastness of geologic time and astronomical
distances. Teachers should provide opportunities for students
to think about space and time in different scales, from the macroscopic
to the microscopic, such as practice in working with relevant numbers
and in visualizing the solar system in the appropriate scale.
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Chapter
and section Numbers
[Not available @ this time.]
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Earth' s
Place in the Universe (20% of CST: 12 items )-
Q 1- 3
[7 items] 1. Astronomy and planetary exploration reveal
the solar system' s structure, scale,
and change over time. As a basis for understanding this concept:
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- Q 1, 2
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a. Students know how the differences and similarities among the
sun, the terrestrial planets,
and the gas planets may have been established during the formation
of the solar system.
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Students studying this standard will learn how the Sun and planets formed and
developed their present characteristics. The solar nebula, a slowly rotating massive cloud of
gas and dust, is believed to have contracted under the influence
of gravitational forces and
eventually formed the Sun, the rocky inner planets, the gaseous outer
planets, and the moons, asteroids,
and comets. The exact mechanism that caused this
event is unknown. The outer planets are condensations of lighter gases that solar
winds blew to the outer solar system when the Sun' s fusion reaction
ignited. Observations supporting this theory are that the orbital planes of the planets are nearly the same and that the planets
revolve around the Sun in the same direction.
To comprehend the vast size of the solar system, students
will need to understand scale, know the speed of light, and be familiar
with units typically used for denoting astronomical distances. For example, Pluto' s
orbital radius can be expressed
as 39.72 AU or 5.96 × 1012 meters
or 5.5 light-hours. An astronomical unit (AU) is a unit of length equal to the mean
distance of Earth from the Sun, approximately 93 million miles. A
light-year, which is approximately 5.88 trillion miles, or 9.46 trillion kilometers, is the distance light can travel
through a vacuum in one year. Students can make a scale model to help them visualize the vast distances in the
solar system and the relative size of the planets and their orbit
around the Sun. Calculator tape may be used to plot these distances
to scale.
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- Q 1-
3
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b. Students know the evidence from
Earth and moon rocks indicates that the solar system was formed from
a nebular cloud of dust and
gas approximately 4.6 billion years ago.
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Since the nineteenth century, geologists, through the use
of relative dating techniques,
have known that Earth is very old. Relative dating methods, however,
are insufficient to identify actual dates for events in the deep
past. The discovery of radioactivity provided science with a "clock". Radioactive dating
of terrestrial samples, lunar samples,
and meteorites indicates
that the Earth and Moon system and meteorites are approximately 4.6
billion years old.
The solar system formed from a nebula, a cloud of gas and debris. Most
of this material consisted of hydrogen and helium created during
the big bang, but the material also included heavier elements formed
by nucleosynthesis in massive
stars that lived and died before the Sun
was formed. The death of a star can produce a spectacular explosion
called a supernova, in which debris rich in heavy
elements is ejected into space as stardust. Strong evidence exists
that the impact of stardust from a nearby supernova triggered the
collapse of the nebula that formed the solar system. The collapse
of a nebula leads to heating, an increase in rotation rate, and flattening.
From this hot, rapidly spinning nebula emerged the Sun and solid
grains of various sizes that later accreted to
form objects that evolved through collisions into planets, moons,
and meteorites. The nebula from which the Sun and planets formed
was composed primarily of hydrogen and helium,
and the solar composition reflects this starting mixture. The nebula
also contained some heavy elements. As the nebula cooled, condensation
of the heavy elements and the loss of volatile elements from the
hot, inner nebula led to formation of rocky inner planets. To varying
extents, the whole of the solar system was fractionated; but the
portion of the solar nebula now occupied by the inner planets was
highly fractionated, losing most of its volatile material, while the outer portion
(beyond Mars) was less fractionated and is consequently richer in
the lighter, more volatile elements.
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- Q 1, 2
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c. Students know the evidence from geological studies of Earth
and other planets suggest that the early Earth was very different
from Earth today.
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The prevailing theory is that Earth formed around 4.6 billion years ago by
the contraction under gravity of gases and dust grains found in a
part of the solar nebula. As Earth accreted, it was heated by the
compressing of its material by gravity and by the kinetic energy
released when moving bits of debris and even planetoids struck and joined. Eventually, the interior of the planet
heated sufficiently for iron, an abundant element in the earth, to
melt. Iron' s high density caused
that element to sink toward the center of Earth. The entire planet differentiated,
creating layers with the lower-density materials rising toward the
top and the higher density materials sinking toward the center. The volatile gases were the least dense and were
“burped out” to form an atmosphere. The result is Earth' s characteristic core, mantle, and
crust and its oceans and atmosphere. Overall, Earth has slowly cooled
since its formation, although radioactive decay has generated some additional heat.
Evidence from drill core samples and surface exposures of very old rocks
reveals that early Earth differed from its present form in the
distribution of water, the composition of
the atmosphere, and the shapes, sizes, and positions of landmasses. Knowing about the evolution of these systems will
help students understand the structure of Earth' s lithosphere,
hydrosphere, and atmosphere.
The composition of the earliest atmosphere was probably
similar to that of present-day volcanic gases, consisting mostly of water
vapor, hydrogen, hydrogen
chloride, carbon monoxide, carbon dioxide, and nitrogen but lacking in free
oxygen. Therefore, no ozone layer existed in the stratosphere to absorb ultraviolet rays, and ultraviolet radiation from the Sun would
have kept the surface of the planet sterile. The oldest fossils, which are of anaerobic organisms, indicate that life on Earth was established sometime before
3.5 billion years ago. Conditions on Earth were suitable for life
to originate here, but the possibility that life hitched a ride to
this planet on a meteorite cannot be excluded. The continents
have slowly differentiated through the partial melting of rocks,
with the lightest portions floating to the top. The absence of atmospheric
oxygen permitted substantial quantities of iron (ferrous) to dissolve,
and some of this iron later precipitated as iron oxide (ferric oxide
or rust) when early photosynthesizers added
oxygen to the atmosphere. This precipitation of iron produced “banded iron formations,” an important
geologic resource for contemporary use. These deposits were formed
only during distinct time periods, generally from one to three billion
years ago. Subsequently, atmospheric oxygen rose sufficiently to
permit multicellular, aerobic organisms to
flourish.
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- Q 1
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d. Students know the evidence indicating that the planets are
much closer to Earth than the stars are.
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Observations of planetary motions relative to the seemingly fixed stars indicate
that planets are much closer to Earth than are the stars. Direct
techniques for measuring distances to planets include radar, which makes use of the Doppler
effect. Distances to some nearby
stars can be measured by parallax: if
a star appears to move slightly with respect to more distant stars
as Earth orbits from one side of the Sun to the other, then the angle
through which the star appears to move and the diameter of Earth' s
orbit determine, by the use of simple trigonometry, the distance
to the star. For more distant stars and extragalactic
objects, indirect methods of
estimating distances have to be used, all of which depend on the
inverse square law of light. This principle states that the
intensity of light observed falls off as the square of
the distance from the source.
Student learning activities may include daily observations of the position of the Sun relative to a known horizon,
observations of the Moon against the same horizon and also relative
to the stars, and observations of planets against the background
of stars. Other activities might take advantage of current data
on the positions of the planets, computer-based lab exercises, and simulations that incorporate the use of library-media center resources.
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- Q 1
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e. Students know the Sun is
a typical star and is powered
by nuclear reactions, primarily the fusion of hydrogen to form helium.
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Comparing the solar spectrum with the spectra of other stars shows that the Sun is a typical star.
Analysis of the spectral features of a star provides information
on a star' s chemical composition and relative abundance of elements.
The most abundant element in the Sun is hydrogen. The Sun' s enormous
energy output is evidence that the Sun is powered by nuclear fusion, the only source of energy
that can produce the calculated total luminosity of the Sun over its lifetime.
Fusion reactions in the Sun convert hydrogen to helium and to some
heavier elements. This conversion is one example of nucleosynthesis, in which the fusion process
forms helium and other elements (see Standard 11.c for chemistry).
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2nd Content
Standard
High school courses in earth sciences will be the first experience for
many students in using physical evidence
to consider models of stellar life cycles and the history of the universe. Students in earlier grades should have observed the patterns of stars in
the sky and learned that the Sun is an average star located in the Milky
Way galaxy. Students should
also have been introduced to astronomical units (AUs), which measure distances between solar system objects
such as Earth and Jupiter. Students should know that distances
between stars, and also between galaxies, are measured in parsecs. The parsec is the distance
at which one astronomical unit subtends one second of arc. This distance
is about 3.26 light-years.
The
concepts dealt with in this standard set are not a part of students'
daily experience. As in the previous
standard set, students may need help to internalize the distance and time scales used to describe the
universe. In addition, misconceptions derived from outdated
hypotheses or from science fiction movies, books, and videos may
interfere with developing an understanding of accepted scientific
evidence. To promote scientific literacy, school libraries should
try to keep their collections up to date. Students
can benefit from the significant amount of new data gained from space
exploration during the past 20 years.
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Chapter
and section Numbers
[Not available @ this time.]
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Earth' s Place in
the Universe (Stars, Galaxies, and the Universe) - Q 1
[ 5 items] 2. Earth-based and space-based astronomy
reveal the structure, scale, and changes in stars, galaxies,
and the universe over time.
As a basis for understanding this concept:
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- Q 1
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a. Students know the solar system is
located in an outer edge of the disc-shaped Milky Way galaxy, which spans 100,000 light
years.
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The solar system is a tiny part of the Milky Way galaxy,
which is a vastly larger system held together by gravity and containing gas, dust, and billions
of stars. Determining the shape of this galaxy is like reconstructing
the shape of a building from the inside. The conception that the
Milky Way galaxy is a disc-shaped
spiral galaxy with a bulging spherical center of stars is
obtained from the location of stars in the galaxy. If viewed under a low-powered telescope from a planet
in another galaxy, the Milky Way would look like a fuzzy patch of
light. If viewed with more powerful telescopes from that far
planet, the Milky Way would look like a typical spiral galaxy. One
would need to travel at the speed
of light for about 100,000 years to go from one edge of the
Milky Way to the galaxy' s opposite edge.
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- Q 1
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b. Students know galaxies are
made of billions of stars and comprise most of the visible mass of
the universe.
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The large-scale structure of the visible, or luminous,
universe consists of stars found by the billions in galaxies. In
turn, there are billions of galaxies in the universe separated from
each other by great distances and found in groups ranging from a
few galaxies to large galaxy clusters with thousands of members. Superclusters are composed of agglomerations of many thousands of
galaxy clusters.
Students should know that scientists catalog galaxies and stars according
to the coordinates of their positions in the sky, their brightness,
and their other physical characteristics. Spectroscopic analysis of the light from
distant stars indicates that the same elements that make up nearby
stars are present in the Sun, although the percentages of heavy
elements may differ.
Matter found in stars makes up most of the mass of
the universe' s visible matter; that is, matter that emits
or reflects light or some other electromagnetic
radiation that is detectable on Earth. The presence of otherwise invisible matter can be inferred from the
effect of its gravity on
visible matter, and the mass of the invisible matter in the universe appears to be even greater than the mass
of the visible. To discover what form this invisible (or "dark")
matter takes is one of the great goals of astrophysics.
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- Q 1
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c. Students know the evidence indicating that all elements with an atomic number greater than
that of lithium have been formed by nuclear fusion in stars.
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Formation of the elements that compose the universe is called nucleosynthesis. Calculations
based on nuclear physics suggest that nucleosynthesis occurred through
the fusing of light elements to make heavier elements. The composition
of distant stars, revealed by their spectra, and the relative abundance of the different elements provide
strong evidence that these calculations are correct.
Theoretical models predict that the only elements that should have formed
during the big bang are hydrogen,
helium, and lithium. All other elements should have formed in the
cores of stars through fusion reactions. Fusion requires that one nucleus approach
another so closely that they touch and bind together. This process
is difficult to accomplish because all nuclei are positively charged and repel their neighbors, creating a barrier that inhibits close
approach. However, the barrier can be bypassed if the nuclei have high velocities because of high temperature. Once
the process begins, fusion of lightweight nuclei leads to a net release
of energy, facilitating further fusion. This mechanism can form elements
with nuclei as large as (but no larger than) those of iron, atomic
number 26. Temperatures sufficient to initiate fusion are attained
in the cores of stars.
In the Sun, and in most stars, hydrogen fusion to form
helium is the primary fusion reaction.
Elements heavier than carbon are formed only in more massive stars
and only during a brief period near the end of their lifetime. A
different type of fusion is necessary to form elements heavier than
iron. This type can be carried out only by adding neutrons to a preexisting
heavy element that forms a “seed.” Neutrons are available only during a limited portion of a star' s lifetime,
particularly during the brief supernova that occurs when a massive star
dies.
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- Q 1
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d. Students know that
stars differ in their life cycles and that visual, radio, and X-ray telescopes may be used to collect data
that reveal those differences.
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Stars differ in size, color, chemical composition, surface gravity, and temperature, all of which affect the spectrum
of the radiation the stars emit and the total energy. It is primarily
the electromagnetic radiation emitted
from the surface of the Sun and stars that can be detected and studied.
Radiation in wavelengths that run from those of X-rays to
those of radio waves can
be collected by modern telescopes.
The data obtained enable astronomers to
classify stars, determine their chemical composition, identify the
stages of their life cycles, and understand their structures. No
one has ever watched a star evolve from birth to death, but astronomers
can predict the ultimate fate of a given star by observing many stars
at different points in their cycles. The primary characteristics
that astronomers use to classify stars are surface temperature and luminosity (the
total energy emitted).
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NE - Q 1
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e.* Students know accelerators boost
subatomic particles to energy levels that simulate conditions in
the stars and in the early history of the universe before stars formed.
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Scientists' understanding of processes occurring in stars
has been enhanced by experiments in particle physics, nuclear physics, and plasma physics. Particle accelerators create particle velocities
great enough for the nuclei of elements to overcome electrostatic
repulsion and to approach close enough for nuclear interactions
to take place, mimicking stellar nuclear fusion processes. The first
accelerator was developed in the 1950s in Berkeley, California. It
allowed the energy of protons to be raised high enough to create antimatter particles,
thereby making it possible to explore the substructure of what had
been considered the most elementary form of matter. Scientists used
the results from these experiments to create models of the processes
and conditions under which matter is created. Developed at the turn
of the twentieth century, Einstein' s special theory of relativity showed that matter and
energy are interchangeable. Particle accelerators made it possible
to produce, in the laboratory, matter-energy transformations previously
possible only in stars. Scientists and engineers continue to look
for ways to control and sustain fusion reactions, a potential source
for a nearly inexhaustible supply of energy.
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NE - Q 1
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f.* Students know the evidence indicating that the color, brightness, and evolution of a star are determined by a balance
between gravitational collapse and nuclear fusion.
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A major concept in science is that temperature is a measure of the underlying energy of motion of
a system. Furthermore, thermal energy can be radiated away into space as electromagnetic
radiation. This process produces the light that Earth receives
from the Sun. As the temperature of a star' s surface increases,
the intensity of radiation produced also increases, and the spectrum
of radiation shifts toward a shorter wavelength.
Consequently, a blue-white star is
hotter than a red star and
emits more energy than does a red star of equal size.
A star' s surface temperature is a guide to the internal
processes occurring within the star. Stars are so hot that they are
a form of matter known as a plasma, in which atoms move so fast that electrons cannot keep
up, leaving the nuclei free as ions. Gravity acts to collapse the ions in the
hot plasma. The high density and high temperature of the plasma allow
the barrier caused by the mutual repulsion of positive nuclei to be overcome, permitting fusion,
or nucleosynthesis, to occur in the stellar core. The energy released from this
reaction helps maintain a pressure that resists further compaction
by the gravitational force and prevents collapse of the stellar core.
The stellar dynamics evolve to a structure that reflects the thermal energy flow from the hot core, where
energy is created, to the cooler surface, where it is radiated away
to space as starlight. The
star will attain an energy balance so that the production of energy
by fusion equals the upward heat flow, which in turn equals the energy
emitted into space. The size and color of the star reflect the balances
needed.
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3rd Content
Standard
The earth sciences use concepts, principles, and theories from the physical sciences and mathematics and often draw
on facts and information from the biological sciences. To
understand Earth' s magnetic field and magnetic patterns of the sea floor, students
will need to recall, or in some cases learn, the basics of magnetism. To understand circulation in the atmosphere, hydrosphere, and lithosphere, students should know about convection, density and
buoyancy, and the Coriolis effect. Earthquake epicenters are located by using geometry.
To understand the formation of igneous and sedimentary minerals, students must master concepts related to crystallization and solution
chemistry.
Because
students in grades nine through twelve may take earth science before
they study chemistry or physics, some background information from the physical sciences
needs to be introduced in sufficient detail. From standards
presented earlier, students should
know about plate tectonics as a driving force that shapes Earth' s surface. They should know that evidence
supporting plate tectonics includes the shape of the continents, the global distribution of fossils and rock types, and the location
of earthquakes and volcanoes. They should also understand that plates
float on a hot, though mostly solid, slowly convecting mantle. They
should be familiar with basic characteristics of volcanoes and earthquakes
and the resulting changes in features of Earth' s surface from volcanic
and earthquake activity.
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Chapter
and section Numbers
[Not available @ this time.]
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Dynamic
Earth Processes (15% of CST: 9 items) - Q 3 - 4
[ 9 items] 3. Plate tectonics operating over geologic time
has changed the patterns of land, sea, and mountains on Earth' s surface.
As the basis for understanding this concept:
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- Q 3 - 4
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a. Students know features of the ocean floor (magnetic patterns, age, and sea-floor topography)
provide evidence of plate tectonics.
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Much of the evidence for continental
drift came from the seafloor rather
than from the continents themselves.
The longest topographic feature in
the world is the midoceanic ridge
system, a chain of volcanoes and rift valleys about 40,000
miles long that rings the planet like the seams of a giant baseball.
A portion of this system is the Mid-Atlantic Ridge, which runs parallel
to the coasts of Europe and Africa and of North and South America
and is located halfway between them. The ridge system is made from
the youngest rock on the ocean floor, and the floor gets progressively
older, symmetrically, on both sides of the ridge. No portion of the
ocean floor is more than about 200 million years old. Sediment is
thin on and near the ridge. Sediment found away from the ridge thickens
and contains progressively older fossils, a phenomenon that also
occurs symmetrically.
Mapping the magnetic field anywhere
across the ridge system produces a striking pattern of high and
low fields in almost perfect symmetrical stripes. A brilliant
piece of scientific detective work inferred that these “zebra stripes”
arose because lava had erupted and cooled, locking into the rocks
a residual magnetic field whose
direction matched that of Earth' s field when cooling took place.
The magnetic field near the rocks is the sum of the residual field
and Earth' s present-day field. Near the lavas that cooled during
times of normal polarity, the residual field points along
Earth' s field; therefore, the total field is high. Near the lavas
that cooled during times of reversed polarity, the residual field
points counter to Earth' s field; therefore, the total field is
low.
The "stripes" provide strong support for the idea of
seafloor spreading because the lava in these stripes can be dated
independently and because regions of reversed polarity correspond
with times of known geomagnetic
field reversals. This theory states that new seafloor is created
by volcanic eruptions at the midoceanic ridge and that this erupted
material continuously spreads out convectively and opens and creates
the ocean basin. At some continental margins deep ocean trenches
mark the places where the oldest ocean floor sinks back into the
mantle to complete the convective cycle. Continental drift and seafloor
spreading form the modern theory of plate tectonics.
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- Q 3 - 4
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b. Students know the principal structures that form at the three
different kinds of plate boundaries.
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There are three different types of plate boundaries, classified
according to their relative motions: divergent boundaries; convergent boundaries; and transform,
or parallel slip, boundaries. Divergent boundaries occur where
plates are spreading apart. Young divergence is characterized by
thin or thinning crust and rift valleys; if divergence goes on long
enough, midocean ridges eventually
develop, such as the Mid-Atlantic Ridge and the East Pacific Rise.
Convergent boundaries occur where plates are moving toward
each other. At a convergent boundary, material that is dense enough,
such as oceanic crust, may sink back into the mantle and produce
a deep ocean trench. This process is known as subduction. The
sinking material may partially melt, producing volcanic
island arcs, such as the Aleutian Islands and Japan. If the
subduction of denser oceanic crust occurs underneath a continent,
a volcanic mountain chain, such as the Andes or the Cascades, is
formed. When two plates collide and both are too light to subduct,
as when one continent crashes into another, the crust is
crumpled and uplifted to produce great mountain chains, such as the
relatively young Himalayas or the more ancient Appalachians.
The third type of plate boundary, called a transform, or parallel
slip, boundary, comes into existence where two plates move
laterally by each other, parallel to the boundary. The San Andreas
fault in California is an important example. Marking the boundary
between the North American and Pacific plates, the fault runs from
the Gulf of California northwest to Mendocino County in northern
California.
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- Q 3 - 4
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c. Students know how to explain the properties of rocks based
on the physical and chemical conditions in which they formed,
including plate tectonic processes.
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Rocks are classified according to their chemical compositions
and textures. The composition reflects the chemical constituents
available when the rock was formed. The texture is an indication
of the conditions of temperature and pressure under which the rock
formed. For example, many igneous rocks, which cooled from molten
material, have interlocking crystalline textures.
Many sedimentary rocks have fragmental textures. Whether formed from
cooling magma, created by deposits of sediment grains in varying
sizes, or transformed by heat and pressure, each rock possesses identifying
properties that reflect its origin.
Plate tectonic processes directly or indirectly control
the distribution of different rock types. Subduction, for example,
takes rocks from close to the surface and drags them down to depths
where they are subjected to increased pressures and temperatures.
Tectonic processes also uplift rocks
so that they are exposed to lower temperatures and pressures and
to the weathering effects of
the atmosphere.
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- Q 3 - 4
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d. Students know why and how earthquakes occur and the scales
used to measure their intensity and
magnitude.
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Most earthquakes are caused by lithospheric plates moving against each other.
Earth' s brittle crust breaks episodically in a stick-and-slip manner.
Plate tectonic stresses build up until enough energy is stored to
overcome the frictional forces at plate boundaries. The magnitude of an earthquake (e.g., as shown on the Richter
scale) is a measure of the amplitude of
an earthquake' s waves. The magnitude depends on the amount of energy that is stored as elastic strain and then released. Magnitude scales are logarithmic,
meaning that each increase of one point on the scale represents a
factor of ten increase in wave amplitude and a factor of about thirty
increase in energy. An earthquake' s intensity (as
measured on a modified Mercalli
scale) is a subjective, but still valuable, measure of how
strong an earthquake felt and how much damage it did at any given
location.
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- Q 3 - 4
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e. Students know there are two kinds of volcanoes: one kind with
violent eruptions producing steep slopes and the other kind with
voluminous lava flows producing gentle slopes.
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The violence of volcanic eruptions is a function of the viscosity of
the lava that erupted. All magmas contain
dissolved volatiles (or gases) that expand and rise buoyantly as
the magma rises to the surface much like the bubbles in a bottle
of soda. Fluid lavas allow gases to bubble away relatively harmlessly,
but viscous lavas trap the gases until large pressures build up and
the system explodes. Temperature and composition determine the viscosity
of magma. Magma at cool temperatures and with a high silica content
is very viscous. Rhyolitic and andesitic lavas are examples of lavas
with high viscosity. They erupt violently, scattering volcanic fragments
and ash widely. Viscous lava, which does not flow very far, builds
steep-sided volcanoes. Other lavas, such as basaltic, are relatively
fluid and erupt quietly, producing great flows of lava that gradually
build gently sloping deposits (called shield volcanoes).
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- Q NE 3 - 4
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f.* Students know the explanation for the location and properties
of volcanoes that are due to hot spots and the explanation for those
that are due to subduction.
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The melting of silica-rich (granitic) upper-crustal rock produces viscous
lavas. The melting of iron-rich (basaltic) lower-crustal, or upper-mantle,
rock produces fluid lavas. Upper-crustal rock may melt at subduction
zones, and violent volcanic eruptions are common there. Lower-crustal
rock may melt at the midocean spreading centers, where quiet, fluid
eruptions are common.
Volcanoes may also arise from the activity
of mantle plumes, which are long-lived hot spots deep in the mantle.
Rock locally melted within the hot spot rises through buoyancy through
the crust, sometimes forming volcanoes. As the magma rises, it melts
other rocks in its path and incorporates them into the magma. The incorporation
of enough upper-crustal rocks, as at the Yellowstone Calder Complex at Yellowstone National Park,
produces explosive volcanoes. If only lower-crustal rocks are incorporated,
as in Hawaii, nonexplosive, gently sloped shield volcanoes form. The
Hawaiian Islands are an example of hot spot volcanism, which occurs
in chains with the volcanoes systematically aging downward away from
the heat source. This type of volcanism is extra evidence supporting
the theory of plate tectonics. Volcanoes form when a particular piece
of the crust is over the hot spot and then die out as that part of
the plate moves off.
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4th Content
Standard
Students know that energy
is transferred from warmer
to cooler objects. They are expected to know that energy is transported
by moving material or in heat flow or as waves. They have learned that when fuel is consumed,
energy is released as heat, which can be transferred by conduction, convection, or radiation. They have also learned
that the Sun is the major source of energy for Earth. They have
studied ways in which heat from Earth' s interior influences conditions
in the atmosphere and oceans and have considered the changes in
weather caused by differences in pressure, temperature, air movement,
and humidity.
Photosynthesis may have been covered in detail
if the students have completed high school biology. Students who have completed high school physics and
chemistry will also be better prepared to deal with transfer and
absorption of energy. To complete this standard set, students should review the characteristics
of the electromagnetic spectrum. Students should also review information presented in the sixth grade science
standards related to dynamic Earth processes to increase their awareness
of the enormous amount of energy stored in the planet, both as original
heat and as a product of radioactive decay. Students should also have studied the mechanisms, primarily mantle convection
and some conduction, that bring heat to Earth' s surface. Students
should know that heat from Earth' s interior escapes into the atmosphere
through volcanic eruptions, hot spring activity, geysers, and similar
means. Although spectacular and energetic, these phenomena
are localized and occur over a tiny percentage of Earth' s surface.
Beyond these readily noticeable losses of interior heat, internal
heat disperses into the atmosphere slowly and relatively uniformly
across the entire surface of the planet.
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Chapter
and section Numbers
[Not available @ this time.]
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Energy in the Earth
System (Solar Energy Enters, Heat Escapes) (30% of CST: 18 items) -
Q 2
[5 items] 4. Energy enters
the Earth system primarily as solar radiation and eventually escapes
as heat. As a basis for understanding this concept:
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- Q 2
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a. Students know the relative amount of incoming solar energy
compared with Earth' s internal energy and the energy used by society.
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Most of the energy that reaches Earth' s surface comes
from the Sun as electromagnetic radiation concentrated in infrared, visible, and ultraviolet wavelengths. The energy available from the Sun' s radiation exceeds
all other sources of energy available at Earth' s surface. There is
energy within Earth, some of which is primitive, or original, heat
from the planet' s formation and some that is generated by the continuing
decay of radioactive elements. Over short periods of time, however,
only a small amount of that energy reaches Earth' s surface. The enormous
amount of energy remaining within Earth powers plate tectonics.
Human
societies use energy for heating, lighting, transportation, and many
other modern conveniences. Most of this energy came to Earth as solar energy. Some has been stored as fossil fuels, plants that stored energy through photosynthesis. Fossil
fuels, including oil, natural gas, and coal, provide the majority
of energy used by contemporary economies. This energy, which has
been stored in crustal rocks during hundreds of millions of years,
is ultimately limited. On average a U.S. household consumes power
at the rate of about 1 kilowatt, or 1,000 joules of energy, per second.
The Sun delivers almost this much power to every square meter of
the illuminated side of Earth. For this reason total energy use by
humans is small relative to the total solar energy incident on Earth
every day, but harvesting this energy economically poses a challenge
to modern engineering.
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- Q 2
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b. Students know the fate of incoming solar radiation in terms
of reflection, absorption, and photosynthesis.
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The fate of incoming solar radiation, which is concentrated
in the visible region of the electromagnetic spectrum, is determined by its wavelength.
Longer wavelength radiation (e.g., infrared)
is absorbed by atmospheric gases. Shorter wavelengths of solar electromagnetic
energy, particularly in the visible range, are not absorbed by the
atmosphere, except for the absorption of ultraviolet radiation by
the ozone layer of the upper
atmosphere. Some of the incident visible solar radiation is reflected
back into space by clouds, dust, and Earth' s surface, and the rest
is absorbed.
Plants and other photosynthetic organisms contain chlorophyll
that absorbs light in the orange, short-red, blue, and ultraviolet
portions of the solar radiation spectrum. The absorption of visible
light is less for green and yellow wavelengths,
the reflection of which accounts for the color of leaves. The
plant uses the absorbed light energy for photosynthesis, in which carbon dioxide and water are converted to sugar, a process that is
used to support plant growth and cell metabolism. A byproduct of
photosynthesis is oxygen. The amount of carbon dioxide in the atmosphere
declines slightly during the summer growing season and increases
again in the winter. The solar energy stored in plants is the primary
energy source for life on Earth.
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5th Content
Standard
Students know that the uneven heating of Earth causes air movements
and that oceans and the water cycle influence weather. They also
know that heat energy is transferred by radiation, conduction, and convection
and that radiation from the Sun is responsible for winds and ocean
currents, which in turn influence the weather and climate. They should
have learned the concept of density and that warm, less-dense fluids
rise and cooler, denser fluids sink (see
Standard Set 8, “Density and Buoyancy,” for grade eight).
Students who have completed courses in chemistry and physics know
that water has high heats of crystallization and evaporation and
high specific heat (see Standard 7.d for chemistry). Others will
have to be introduced to these concepts. This knowledge provides
a foundation of physical principles for a fuller understanding of
energy flow through Earth' s system.
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Chapter
and section Numbers
[Not available @ this time.]
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Energy in the Earth System (Ocean and
Atmospheric Convection) - Q 2 - 3
[8 items] 5. Heating of Earth' s surface and atmosphere by the sun drives
convection within the atmosphere and oceans, producing winds and
ocean currents. As a basis for under-standing this
concept:
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- Q 2
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a. Students know how differential heating of Earth results in
circulation patterns in the atmosphere and oceans that globally distribute
the heat.
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The Sun' s rays spread unequally across Earth' s surface,
heating it more at the equator and less at the poles. As heat at the surface transfers to the atmosphere,
circulation cells are created. At the equator, for example, hot,
moist air rises, expands under lower atmospheric pressure, and cools,
causing the air to release its water as precipitation. The air then moves either north or south away from
the equator. In its eventual descent the air is compressed by higher
atmospheric pressure and warms. Therefore, the air arrives at Earth' s
surface in a state of low relative
humidity. The air then flows back to the equator, completing
the cycle. There are three such cycles (or cells) between the equator
and the pole. The circulation in
these cells regulates the general pattern of rainfall on Earth' s
surface, with wet climates to
be found under ascending air and dry climates under descending air.
Therefore, wet climates are generally found at the equator, dry climates
in bands at around 30 degrees north and south, wet climates in bands
at around 60 degrees, and dry climates again at still higher latitudes.
The same unequal heating of Earth' s surface that drives
the global atmospheric circulation also causes large thermally driven currents in
the oceans. These currents are important in global redistribution
of heat. Air currents also distribute heat. Some of the atmospheric
heat transport is carried out by exchanging warm and cold air, but
water vapor is also a major transport mechanism. Heat is
stored in water that evaporates at low latitudes and
then is released when the water recondenses (as precipitation) at
higher latitudes. For all these reasons combined, the equatorial regions are somewhat cooler, and the poles somewhat warmer,
than might otherwise be expected.
Earth' s axis is tilted with respect to the plane of its orbit around the Sun.
As a result, different amounts of solar energy reach the two hemispheres at
different times, thus causing the seasons. The ocean and atmosphere
are a linked system as energy is exchanged between them. Ocean currents
rise in part because cool or more saline waters descend, setting
circulation patterns in motion. These currents also distribute heat
from the equator toward the pole.
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- Q 2
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b. Students know the relationship between the rotation of Earth
and the circular motions of ocean currents and air in pressure centers.
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Earth rotates on an axis, and all flow of fluids on or below the surface appears to be
deflected by the Coriolis effect, making right turns in the Northern Hemisphere and
left turns in the south. This is a
complicated phenomenon to explain to students, but it can be illustrated
with a rotatable globe and chalk. Students can hold the globe still
and draw a chalk line from the North Pole to the equator and another
from the South Pole to the equator. The result will be a part of
a great circle. Next the students draw the same line while, at the
same time, slowly rotating the globe. A curved line will appear.
The faster the globe turns, the more profound the turning of the
chalk line. Teachers may find it helpful to compare this effect with
centrifugal force, another apparent force arising from an accelerating
reference frame. Many good demonstrations of this phenomenon are
possible. Teachers can also point out to students that the airflow
past a bicycle rider feels the same if the bicycle is still and the
air is moving or vice versa. An observer standing on Earth feels
that the air is moving, even if the relative motion arises because
he or she and Earth are moving through the air.
Combining convective air or water flows with Coriolis
turning produces circular currents. For example, when a region, or cell,
of lower-pressure (less dense)
air exists in the Northern Hemisphere, higher-pressure air tries to flow toward it from all sides
by convection. However, the Coriolis effect deflects these flows
to the right, leading to a circular airflow, which appears counterclockwise
when viewed from above.
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- Q 2
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c. Students know the origin and effects of temperature inversions.
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Normally,
the atmosphere is heated from below by the transfer of energy from
Earth' s surface. This activity produces convection, the transfer
of heat by the vertical movements of air masses. However, in certain
geographical settings, local sources or sinks for heat can interact
with topography to create circumstances in which
lower-density warm air, flowing from one direction, is emplaced over
higher-density cool air that has come from another direction. This
situation, called a temperature inversion, effectively stops convection, causing stagnant air.
In areas with high population density (or with other sources of pollution)
atmospheric pollutants, known as smog, may be trapped by the inversion.
In southern California inverted air occurs normally during the late spring
and summer, when the land' s temperature is significantly warmer
than the ocean' s. Air that has been cooled over the ocean flows
inland but is stopped by the mountains. Airflow from the deserts,
which are at higher elevations, provides warm air that caps this
cool marine layer, producing an inversion. This low-elevation,
cooler air is held in place by mountains ringing the Los Angeles
Basin and is rapidly filled with pollutants.
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- Q 3
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d. Students know properties of ocean water, such as temperature
and salinity, can be used to
explain the layered structure of the oceans, the generation of horizontal
and vertical ocean currents, and the geographic distribution of marine
organisms.
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In low latitudes water is warmed at the surface
by the Sun. Differences in the density of water force this water to flow
to high latitudes, where it
cools as it transfers thermal energy into the atmosphere. Because cooling
increases water' s density (down to a temperature of 4 degrees Celsius
in the case of fresh water and down to the freezing point in the case
of sea water), water sinks at high latitudes, flows back toward the
equator at depth, and upwells toward the surface as it is warmed by
the Sun. This density-driven circulation creates a layered ocean structure
at low and midlatitudes, with warm low-density water
at the surface and cool high-density water at depth. Salinity also plays a role because rapid evaporation in
dry-latitude belts concentrates the salt. Fresh water inflowing from
rainfall in wet climatic belts, from rivers, and from melting ice formed
at high latitudes decreases salinity. Because water has a high specific heat, it effectively transports
heat from the equator to the poles. Furthermore, the high specific
heat helps to buffer Earth' s surface against significant daily or seasonal
temperature changes. Ice, the solid phase of water, is less dense than
the liquid phase and thus floats. (This unique property of water is
important to life on Earth.) Icebergs float long distances from their
places of origin before they melt and add fresh water to the surface
of the ocean. Water is an excellent solvent
for many ions and dissolved gases necessary to sustain marine life.
The ocean' s chemistry reflects the combined influences of ocean circulation
and of marine organisms on biologically active compounds. Water near
the surface is oxygenated by photosynthesis, and dissolved nutrients
required by phytoplankton are depleted. Zooplankton eat phytoplankton, and the remains of both sink
into deeper waters where they decompose. The decomposition enriches
deep water in nutrients and depletes it in oxygen, leading to a chemically
stratified ocean. Deep water upwelled into the surface zone carries abundant nutrients needed
to sustain the growth of phytoplankton. These patterns influence the
distribution of marine life because organisms tend to follow and stay
within zones that best meet their requirements for survival. In addition to the density factors
that drive ocean circulation, a wind-driven circulation exists in surface
waters. These surface and deep currents mix the oceans continuously,
particularly at the surface. Ocean currents influence regional climates.
For example, the Gulf Stream brings warm water offshore to northwest
Europe, warming the climate in such countries as Great Britain. Without
these currents the climate would
be very different. To demonstrate the
density of currents, teachers can use containers of water heated to
different temperatures. Food coloring may be used to dye hot water
one color and cold water another. The students observe as the hot water is poured into the cold water and vice versa. To extend
the demonstration further, the teacher can add table salt to make different
concentrations of salt in same- and different-colored water samples.
As the teacher pours saline water into fresh water, and vice versa,
students can observe and report what happens.
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- Q 2
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e. Students know rain forests
and deserts on Earth are
distributed in bands at specific latitudes.
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Latitudinal bands, or zones, of similar climatic conditions
circle Earth. These bands are produced by the large-scale convective air patterns described earlier,
known as “Hadley cells.”
Basically, air rises at the equator and at near 60 degrees north
and south latitudes and sinks near 30 degrees north and south latitudes
and at both poles. Students
will learn these concepts more easily if they understand the ideal gas law and also the notion of relative humidity that cooler air evaporates less water than does warmer air. If students have
not studied these topics, the teacher can explain that sinking air
is compressed because
of gravity' s pull on the overlying air. Rising air expands and cools,
and sinking air is compressed and heated (e.g., compressing air into
a bicycle tire warms the air). Because more water can evaporate at
warmer temperatures, the air seems drier as it is compressed and
heated. Therefore, deserts are common in bands of sinking air and,
conversely, high precipitation in zones of rising air supports lush vegetation (e.g., rainforests).
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NE - Q 2
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f.* Students know the interaction of wind patterns, ocean currents, and mountain ranges results in the global pattern
of latitudinal bands of rain forests and deserts.
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As air is warmed in the tropics, water is evaporated,
and the resulting warm, moist air rises and cools. When this moist
tropical air cools enough, it becomes saturated
and precipitates water as rain. The once warm, moist air is now dryer
and
cold and heavy. This air is then displaced to the north or south
by rising currents of warm, moist air. The cold, dry air begins to
descend and is again compressed and heated. At last reaching the
ground, at about 30 degrees latitude, the now warm, dry air evaporates
water from the ground, producing a desert. A similar pattern is seen
farther north and south, where temperate rainforests exist at about
60 degrees latitude, reflecting the rising air in that region. The
air sinks at the poles and is warmed somewhat but is still very cold
and dry.
Deserts, called rain shadow deserts, are also found outside the latitudinal
band of deserts. An example is the desert in much of Nevada east
of the Sierra Nevada. Warm, moist winds blowing off the Pacific Ocean
rise up over the Sierra Nevada, cooling and dropping rain on the
forested westward side of the mountains. East of the mountains the
air, which is dry, drops down to lower elevations, heats up, and
evaporates surface water, producing a desert. Global weather and atmospheric circulation maps from the weather bureau are helpful for studying this
process. Such maps can be downloaded from appropriate Internet sites. Students may search an
atlas for maps that show the distribution of deserts and rain forests
and compare those maps with global weather maps. Students can plot atmospheric and oceanic currents
on a world map and identify regions that are warm and wet and those that are
cold and dry.
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6th Content
Standards
This standard set is designed to help students focus on
the various factors that produce climate and weather. Since the study of the water (hydrologic) cycle is fundamental to
understanding weather, teachers should review that cycle during the study of Standard Set
6. In standard sets taught previously in the lower grade levels, weather
was introduced, as a phenomenon, followed by a discussion of the
procedures in which weather is observed, measured, and described. Subsequently,
weather maps were introduced, and students
should have learned to read and interpret topographic maps.
The Investigation and Experimentation standards for grades six and seven also called for students to construct scale models and make predictions from accumulated evidence. Teachers should review the concept of pressure with
the students.
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Chapter
and section Numbers
[Not available @ this time.]
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Energy in the Earth System (Climate
and Weather) - Q 3
[ 5 items] 6. Climate is the long-term average of a region' s
weather and depends on many factors. As a basis for understanding
this concept:
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- Q 3
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a. Students know weather (in
the short run) and climate (in the long run) involve the transfer of energy into and out of the atmosphere.
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Unequal transmission and absorption of solar energy cause differences in air temperature and
therefore differences in pressure; winds are generated as a result. Solar-influenced evaporation and precipitation of
water determine the humidity of
the atmosphere. Evaporation and precipitation also transfer energy between the atmosphere and oceans because energy
is absorbed when water evaporates and is released when water condenses.
Climate is the long-term average of weather. According to an old
saying, “Climate is what you expect, and weather is what you get.”
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- Q 3
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b. Students know the effects on climate of latitude, elevation, topography, and proximity to large bodies of water and cold
or warm ocean currents.
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Previous earth science standards covered how and why the
locations of rainforests and deserts depend on latitude. But other variables can
modify the climate in a particular region. For example, since air
expands and cools when it rises, expected temperatures at high elevations are considerably lower than they
are at sea level or below. Mountains also affect local climate because
of the rain-shadow effect,
described in Standard Set 5, “Energy in the Earth System,” in this section, and
the direction of prevailing winds.
The Indian monsoon cycle and the smaller-scale Santa Ana winds are other examples of how
mountains may influence weather and climate.
The proximity of land to large bodies of water can also strongly influence
climate. Large-scale warm and cold oceanic currents (e.g., the cold Japanese
current off the coast of California and the warm Gulf Stream off
the East Coast of the United States) exert regional controls on the
climate of adjoining landmasses. Even more important, water has a
very high specific heat,
which causes water to remain within a relatively narrow temperature
range between day and night and from season to season. Because of
this phenomenon, regions near bodies of water have a tempered climate
generally cooler than inland regions during hot weather and warmer
than inland regions during cold weather.
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- Q 3
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c. Students know how Earth' s climate has changed over time, corresponding
to changes in Earth' s geography, atmospheric composition, and other factors, such as solar radiation and plate movement.
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Because Earth is dynamic, particularly with regard to long-term
changes in the distribution of continents caused by plate tectonic movements, the planet' s climate
has changed over time. Some geologic eras were much warmer than the
present Cenozoic era. At other times much of the land was covered
in giant ice sheets.
Astronomical factors that vary significantly only over millenia and
such factors as changes in the tilt of Earth' s axis of rotation and changes in the shape of Earth' s
orbit also influence climate. The configuration of continental landmasses affects ocean currents. Climate
is affected, episodically, by volcanic eruptions and impacts of meteorites that inject dust into
the atmosphere. Dust and volcanic ash reduce the amount of energy
penetrating the atmosphere, thereby changing atmospheric circulation, rainfall
patterns, and Earth' s surface temperatures.
Variations in life in general, and human activity in particular,
affect the amounts of carbon dioxide and other gases that enter the atmosphere. The
effect of carbon dioxide and other greenhouse gases is discussed in Standard
4.d in this section.
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7th Content
Standard
Students who complete high school biology/life sciences before they
take earth sciences will already have learned about biogeochemical cycles. Through standards presented in lower grade levels,
other students should have been exposed to life cycles, food chains, and the movement of chemical elements through biological and physical systems.
Students should also have studied chemical changes in organisms and
should know that through photosynthesis solar energy is used to create
the molecules needed by plants. In this standard set students will learn that within the biogeochemical
cycles, matter is transferred between organisms through food webs or chains. Matter can also be transferred from
these cycles into physical environments where the cycling elements are
held in reservoirs. Matter can be transferred back into biological
cycles through physical processes, such as volcanic eruptions
and products of the rock cycle, particularly those from weathering.
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Chapter
and section Numbers
[Not available @ this time.]
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Biogeochemical
Cycles (8.3 % of CST: 5 items)- Q 3 - 4
[5 items] 7. Each element on Earth
moves among reservoirs, which
exist in the solid earth, in oceans, in the atmosphere, and within
and among organisms as part of biogeochemical cycles.
As a basis for understanding this concept:
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- Q 3
- 4
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a. Students know the carbon cycle of photosynthesis and respiration
and the nitrogen cycle.
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Carbon and nitrogen move through biogeochemical cycles. The recycling of these components in
the environment is crucial to the maintenance of life. Through photosynthesis,
carbon is incorporated into the biosphere from
the atmosphere. It is then
released back into the atmosphere through respiration.
Carbon dioxide in the atmosphere is dissolved and stored in the ocean
as carbonate and bicarbonate ions, which organisms
take in to make their shells. When these organisms die, their shells
rain down to the ocean floor, where they may be dissolved if the
water is not saturated in carbonate. Otherwise, the shells are deposited
on the ocean floor and become incorporated into the sediment, eventually turning into a bed of
carbonate rock, such as limestone.
Uplifted limestone may dissolve in acidic rain to return carbon to the atmosphere
as carbon dioxide, sending calcium ions back into the ocean where
they will precipitate with carbon dioxide to form new carbonate material.
Carbonate rocks may also be subducted, heated to high temperatures, and decomposed, returning carbon to the atmosphere
as volcanic carbon dioxide gas. Carbon is also stored in the solid
earth as graphite, methane
gas, petroleum, or coal.
Nitrogen, another element important to life, also cycles through the
biosphere and environment. Nitrogen gas makes up most of the atmosphere,
but elemental nitrogen is relatively inert, and multicellular plants and animals
cannot use it directly. Nitrogen must be “fixed,” or converted to ammonia, by specialized
bacteria. Other bacteria change ammonia to nitrite and then to nitrate,
which plants can use as a nutrient. Eventually, decomposer bacteria
return nitrogen to the atmosphere by reversing this process.
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- Q 3
- 4
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b. Students know the global carbon
cycle: the different physical and chemical forms of carbon
in the atmosphere, oceans, biomass, fossil fuels, and the movement of carbon among these reservoirs.
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The global carbon cycle extends across physical and biological
Earth systems. Carbon is held temporarily in a number of reservoirs,
such as in biomass, the atmosphere,
oceans, and in fossil fuels. Carbon appears primarily as carbon dioxide
in the atmosphere. In oceans carbon takes the form of dissolved carbon
dioxide and of bicarbonate and carbonate ions. In the biosphere carbon
takes the form of sugar and of many other organic molecules in living
organisms. Some movement of carbon between reservoirs takes
place through biological means, such as respiration and photosynthesis,
or through physical means, such as those related to plate
tectonics and the geologic
cycle. Carbon fixed into the biosphere and then transformed into coal, oil, and gas deposits
within the solid earth has in recent years been returning to the
atmosphere through the burning of fossil fuels to generate energy.
This release of carbon has increased the concentration of carbon dioxide in the atmosphere. Carbon dioxide
is a primary greenhouse gas, and its concentration in the atmosphere
is tied to climatic conditions.
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- Q 3
- 4
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c. Students know the movement of matter among reservoirs is driven
by Earth' s internal and external sources
of energy.
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The energy to move carbon from one reservoir to another
originates either from solar energy or as heat from Earth' s interior. For example, the energy
that plants use for photosynthesis comes directly from the Sun, and the heat that drives subduction comes
from the solid earth.
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NE - Q 3 - 4
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d.* Students know the relative residence times and flow characteristics of carbon in and out of its
different reservoirs.
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Carbon moves at different rates from one reservoir to another, measured
by its residence time in any particular reservoir. For example, carbon
may move quickly from the biomass to the atmosphere and back because
its residence time in organisms is relatively short and the processes
of photosynthesis and respiration are relatively fast. Carbon may
move very slowly from a coal deposit or a fossil fuel to the atmosphere
because its residence time in the coal bed is long and oxidation
of coal by weathering processes is relatively slow.
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8th Content
Standards
Students have little direct background on the structure and composition
of the atmosphere beyond what they have learned from Standard Set 7, “Biogeochemical Cycles.” If studying
earth sciences, they will know how organisms exert chemical influences
on the air around them through photosynthesis and respiration.
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Chapter
and section Numbers
[Not available @ this time.]
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Structure and Composition of the Atmosphere (8.3 % of CST: 5 items)-
Q 2
[ 5 items] 8. Life has changed Earth' s atmosphere, and
changes in the atmosphere affect conditions for life. As a basis
for understanding this concept:
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- Q 2
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a. Students know the thermal structure and chemical composition
of the atmosphere.
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The atmosphere is a mixture of gases: nitrogen (78 percent), oxygen (21
percent), argon (1 percent), and trace gases, such as water vapor
and carbon dioxide. Gravity pulls
air toward Earth, and the atmosphere gradually becomes less dense
as elevation increases. The atmosphere is classified into four layers
according to the temperature gradient. The temperature decreases
with altitude in the troposphere, the first layer; then similarly increases in the stratosphere,
the second layer; decreases in the mesosphere,
the third layer; and increases in the thermosphere (ionosphere), the fourth layer.
The troposphere, the layer in which weather occurs,
supports life on Earth. The stratosphere is less dense than
the troposphere but has a similar composition except that this second
layer is nearly devoid of water. The other difference is that solar
radiation ionizes atoms in the stratosphere and dissociates oxygen
to form ozone, O3. This process is important to life
on Earth because ozone absorbs harmful ultraviolet
radiation that would otherwise cause health problems. Air
in the mesosphere has very low density and is ionized by solar radiation. The thermosphere, the
outermost layer of the atmosphere, is almost devoid of air and receives the direct rays of the Sun. The
thermosphere provides a good illustration of the difference between
temperature and heat. Temperature is high there because the little
heat absorbed is distributed among very few molecules, keeping the
average energy of each molecule high.
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- Q 2
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b. Students know how the composition of Earth' s atmosphere has evolved over geologic
time and know the effect of out-gassing,
the variations of carbon dioxide concentration, and the origin
of atmospheric oxygen.
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During the early history of the solar system, strong solar winds drove the primordial atmosphere away. This atmosphere
was then replaced by a combination of gases released from Earth (out-gassing),
mostly through volcanic action, and by bombardment of materials from comets and asteroids. Chemical reactions through time, in the presence
of water, changed the atmosphere' s original methane and ammonia into
nitrogen, hydrogen, and carbon dioxide. Lightweight hydrogen escaped,
leaving a predominance of nitrogen. As life capable of photosynthesis developed on Earth, carbon
dioxide was taken up by plants, and oxygen was released. The present
balance of gases in the atmosphere was achieved at least 600 million years
ago. Small but important variations in
the amount of carbon dioxide in the atmosphere have occurred naturally
since then. Significant increases have been measured in modern times and attributed
in large part to human activities, such as the burning of fossil
fuels.
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- Q 2
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c. Students know the location of the ozone layer in the upper atmosphere, its role in absorbing ultraviolet
radiation, and the way in which this layer varies both naturally
and in response to human activities.
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The ozone layer in the stratosphere is formed when high-energy
solar radiation. By absorbing ultraviolet radiation, the ozone eventually converts interacts with
diatomic oxygen molecules (O2) to produce ozone, a triatomic oxygen molecule (O3 back to diatomic
oxygen O2). This absorption of ultraviolet radiation
in the stratosphere reduces radiation levels at Earth' s surface and mitigates harmful effects on plants and animals.
The formation and destruction of ozone creates an equilibrium
concentration of ozone in the stratosphere. A reduction in
stratospheric ozone near the poles has been detected, believed to
be caused by the release of chlorofluorocarbons
(CFCs), such as those used as working fluids in air conditioners.
The halogens in these CFCs interfere with the
formation of ozone by acting as catalysts substances that modify the rate of a reaction without
being consumed in the process. As catalysts, a few molecules of CFCs can help
to eliminate hundreds of ozone molecules in the stratosphere. While
ozone is beneficial in the stratosphere, it is also a manufactured photochemical
pollutant in the lower atmosphere. Students should be taught the importance of reducing the level of ozone in
the troposphere and of maintaining the concentration of that gas
in the stratosphere.
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9th Content
Standard
Students
should already know that mountains, faults,
and volcanoes in California result from plate tectonic activity and that flowing surface water is the most important agent in
shaping the California landscape. The topics in this standard set
can be covered as a separate unit or as a part of a unit included in other topics addressed by the standards.
A specific discussion of California earthquakes can be introduced in the teaching
of Standard Set 3, “Dynamic Earth Processes,” in this section.
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Chapter
and section Numbers
[Not available @ this time.]
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California
Geology (8.3 % of CST: 5 items)- Q 1- 4
[ 5 items] 9. The geology
of California underlies the state' s wealth of natural
resources as well as its natural
hazards. As a basis for understanding this concept:
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- Q 1-
4
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a. Students know the resources of major economic importance in
California and their relation to California' s geology.
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Many of the important natural resources of California are related
to geology. The Central Valley
is a major agricultural area and a source of oil and natural gas because of deposition of sediments in
the valley, which was created by faulting that occurred simultaneously as the Sierra Nevada was elevated tectonically.
California' s valuable ore deposits
(e.g., gold) came into existence during the formation of large igneous intrusions, when molten
igneous rock was injected into older rocks. Geothermal
energy resources are related to mountain building and to plate
tectonic spreading, or rifting, of the continent.
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- Q 1-
4
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b. Students know the principal natural hazards in different California
regions and the geologic basis of those hazards.
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California is subject to a variety of natural hazards.
Active fault zones generate earthquakes, such as those of the San
Andreas fault system. Uplifted areas
with weak underlying rocks and sediments are prone to landslides, and the California Cascade mountains
contain both active and dormant volcanoes. The erosion of coastal
cliffs is expected, caused in part by the energy of waves eroding them at their bases. When earthquakes
occur along the Pacific Rim, seismic sea waves, or tsunamis, may be generated.
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- Q 1-
4
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c. Students know the importance
of water to society, the origins of California' s fresh water, and the relationship between
supply and need.
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Water is especially important in California because its
economy is based on agriculture and industry, both of which require
large quantities of water. California is blessed with an abundance
of fresh water, which is supplied by precipitation and collected from the melting of the snowpack in
watersheds located in the Sierra Nevada and in other mountain ranges.
This process ensures a slow runoff of water following the winter
rains and snowfall. But the water is not distributed evenly. Northern
California receives most of the rain and snowfall, and southern California
is arid to semiarid. The natural distribution of water
is adjusted through engineered projects that transport water in canals from
the northern to the southern part of the state.
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NE - 1- 4
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d.* Students know how to analyze published geologic hazard maps
of California and know how to use the map' s information to identify evidence of geologic
events of the past and predict geologic changes in the future.
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Students who learn to read and analyze published
geological hazard maps will be able to make better personal decisions about the safety of business and residential locations.
They will also be able to make intelligent voting decisions relative to public land use and remediation of hazards.
A wealth of information pertaining to these content standards for earth science
is readily available, much of it on the Internet. County
governments have agencies that dispense information about resources and hazards, often related to issuing permits
and collecting taxes. The California Division of Mines and Geology
is an excellent state-level resource. Federal agencies that supply
useful information about California resources and hazards are the
U.S. Geological Survey, the Federal Emergency Management Agency,
and the U.S. Army Corps of Engineers.
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Investigation and Experimentation Content Standard
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Chapter
and section Numbers
[Not
available @ this time.]
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Investigation and Experimentation (10% of
CST: 6 items) - Q 1,
2, 3, 4
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- Q 1, 2, 3, 4
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a. Select and use appropriate tools and technology (such
as computer- inked probes, spreadsheets, and graphing calculators)
to perform tests, collect data, analyze relationships,
and display data.
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- Q 1, 2, 3, 4
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b. Identify and communicate sources
of unavoidable experimental error.
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- Q 1, 2, 3, 4
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c. Identify possible reasons
for inconsistent results, such as sources of error or uncontrolled conditions.
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- Q 1, 2, 3, 4
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d. Formulate explanations
by using logic and evidence.
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- Q 1, 2, 3, 4
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e. Solve scientific problems
by using quadratic equations and simple trigonometric, exponential,
and logarithmic functions.
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