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2
Earth’s Physical Systems:
Matter, Energy, and
Geology
Chapter Objectives
This chapter will help students:
Explain the fundamentals of matter and chemistry and apply them to real-world
situations
Differentiate among forms of energy and explain the basics of energy flow
Distinguish photosynthesis, cellular respiration, and chemosynthesis, and
summarize their importance to living things
Explain how plate tectonics and the rock cycle shape the landscape around us
and the earth beneath our feet
List major types of geologic hazards and describe ways to mitigate their impacts
Lecture Outline
I.
Central Case: Clean Green Energy Beneath Our Feet, The Geysers in California
A. By tapping reservoirs of steam produced by hot rocks underground,
engineers are using geothermal energy, which produces enough
electricity at the Geysers in California to power nearly a million homes.
B. To counter the depletion of the underground reservoirs, managers began
to import wastewater from surrounding communities and inject it into the
ground.
C. Earthquakes have emerged as a consequence of the extraction of steam
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and the pumping of water into the reservoirs. So far, these have all been
minor but there are fears of larger ones.
D. Currently, the Geysers provide one-fourth of California’s renewable energy.
II.
Matter, Chemistry, and the Environment
1. All material in the universe that has mass and occupies space is termed
matter.
2. The ways in which various types of matter interact is called chemistry.
A. Matter is conserved.
1. Matter may be transformed from one type of substance into others, but
it cannot be created or destroyed. This principle is referred to as the
law of conservation of matter.
2. The amount of matter stays constant as it is recycled in nutrient cycles
and ecosystems. Pollution and waste will not simply disappear when
we dispose of it.
B. Atoms and elements are the chemical building blocks.
1. The geothermally-heated water at the Geysers is made of hydrogen
and oxygen. Both are elements.
2. An element is a fundamental type of matter, a chemical substance
with a given set of properties that cannot be broken down into
substances with other properties.
3. Other than hydrogen and oxygen, especially abundant elements on our
planet include silicon, nitrogen, and carbon. The periodic table
organizes the elements according to their chemical properties and
behavior.
4. Atoms are the smallest units that maintain the chemical properties of
the element. Each element has a defined number of protons in its
nucleus and this defines its atomic number. The combined number of
protons and neutrons in the nucleus determines the element’s mass
number.
5. The nucleus is surrounded by negatively charged particles known as
electrons, which balance the positive charge of the protons.
C. Isotopes
1. Atoms of a given element may contain different numbers of neutrons.
Atoms of the same element with differing numbers of neutrons are
referred to as isotopes.
2. Some isotopes are radioactive and decay into lighter radioisotopes
until they become stable isotopes (not radioactive).
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3. Each radioisotope decays at a rate determined by that isotope’s halflife. Uranium-235, our source for nuclear power, decays with a half-life
of about 700 million years, eventually forming a stable lead isotope.
D. Ions
1. Atoms may gain or lose electrons and become ions, electrically
charged atoms. In this state, they may combine with other atoms.
E. Atoms bond to from molecules and compounds.
1. Atoms bond together and form molecules, combinations of two or
more atoms. Some common gasses such as hydrogen, H2, and oxygen,
O2, are typical.
2. A molecule composed of atoms to two or more different elements is called a
compound. Water is a compound made of two hydrogen atoms bound to
one oxygen atom. Another important compound is carbon dioxide,
consisting of one carbon atom bonded to two oxygen atoms.
3. Atoms bond together as a result of an attraction for one another’s
electrons. These vary from equal sharing, such as in hydrogen gas, to
water where the oxygen attracts the electrons more strongly, to
compounds where the electron is transferred from one element to
another. Compounds exhibiting this last type of bonding are known as
ionic compounds, or salts.
4. Elements, molecules, and compounds can come together in mixtures
without chemically bonding. Homogeneous mixtures are called
solutions. Air in the atmosphere is a solution of many constituents,
including nitrogen, oxygen, water vapor, methane, and ozone.
F. Water’s chemistry facilitates life.
1. Water has properties that give it a unique capacity to support life. A
partial negative charge at the oxygen atom and a partial positive
charge at the hydrogen atom allow water molecules to adhere to one
another in a weak attraction called a hydrogen bond.
2. Hydrogen bonding gives water properties such as cohesion, high heat
absorption capacity, a solid form that is less dense than the liquid
form, and an ability to dissolve, or hold in solution, many other
molecules, particularly ions and other partially charged molecules.
G. Hydrogen ions determine acidity.
1. In aqueous solution, a small number of water molecules split apart,
forming a hydrogen ion (H+) and a hydroxide ion (OH–). The product
of these ion concentrations are always the same; if one increases, the
other decreases.
2. Solutions in which H+ concentration are greater than OH- are acidic.
The reverse case creates solutions which are basic, or alkaline.
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3. The pH scale quantifies the acidity or alkalinity. pH less than 7
indicates an acidic solution; pH greater than y indicates an alkaline
solution. Pure water has a pH of 7.
4. The pH scale is logarithmic; each step represents a tenfold difference
in hydrogen ion concentration.
H. Matter is composed of organic and inorganic compounds.
1. Organic compounds consist of carbon atoms and, generally,
hydrogen atoms, and may include other elements. When carbon atoms
bond together in long chains, the resulting molecules may be called
polymers.
2. One class of organic compounds that is important in environmental
science is hydrocarbons, which contain only atoms of carbon and
hydrogen.
3. The lightest hydrocarbons, containing four or fewer carbon atoms, are
gasses. Hydrocarbons with between four and 20 carbon atoms are
generally liquids; those having more than 20 are usually solids.
4. Some hydrocarbons, such as the polycyclic aromatic hydrocarbons,
PAHs, are found in gasoline and oil as well as in combustion products
and are known to be toxic to wildlife and humans.
I.
Macromolecules are building blocks of life.
1. Some polymers, proteins, nucleic acids, and carbohydrates play key
roles as building blocks of life. Along with lipids, fats, oils, and
waxes, these molecules are referred to as macromolecules because of
their large sizes.
2. Proteins consist of long chains of organic molecules called amino
acids. They serve many different functions in living cells, providing
structural support, energy storage, and immune system functions.
They also act as chemical messengers as hormones, and chemical
reaction catalysts as enzymes.
3. Nucleic acids direct the production of proteins. Deoxyribonucleic
acid (DNA) and ribonucleic acid (RNA) carry the hereditary
information for organisms. Nucleic acids are composed of nucleotides,
each of which contains a sugar molecule, a phosphate group, and a
nitrogenous base. Regions of DNA that code for specific functions are
called genes.
4. Carbohydrates include simple sugars that are 3 to 7 carbon atoms
long. Among these is glucose, which fuels living cells and serves as
the base for complex carbohydrates. Complex carbohydrates include
starch, an energy storage compound, chitin, a structural component of
shells, and cellulose, the most abundant organic compound on earth,
found in the cell walls of plants.
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J.
We create synthetic polymers.
1. Chemists work with the polymer concept and create polymers called
plastics.
2. Polyethylene, polypropylene, polyurethane, and polystyrene are just a
few of the many synthetic polymers in our manufactured products.
3. We value polymers because they are long-lasting and resist chemical
breakdown – the same traits that make them a serious source of waste
and pollution, which endangers wildlife and human health.
III. Energy: An Introduction
1. Energy is the capacity to change the position, physical composition,
or temperature of matter – in other words, a force than can accomplish
work.
A. Energy comes in different forms.
1. Potential energy is the energy of position.
2. Kinetic energy is the energy of motion. It can be expressed as heat
energy, light energy, sound energy, or electrical energy as well.
3. Chemical energy is a special type of potential energy that is held in the
bonds between atoms. Converting a molecule with high-energy bonds
into molecules with lower-energy bonds releases energy by changing
potential energy into kinetic energy.
4. Nuclear energy, the energy in an atomic nucleus, and mechanical
energy, such as that stored in a compressed spring, are also potential
energies.
B. Energy is always conserved but can change in quality.
1. The first law of thermodynamics states that energy can change from
one form to another, but cannot be created or lost. For example, when
heated underground water surges to the surface, the kinetic energy of
its movement will equal the potential energy it held underground.
2. The second law of thermodynamics states that energy tends to
change from a more-ordered state to a less-ordered state, as long as no
force counteracts this tendency. Systems tend to move toward
increasing disorder, or entropy.
3. The order of an object or system can be increased through the input of
additional energy from outside the system. Living organisms maintain
their structure and function by consuming energy (food).
4. The nature of an energy source determines how easily people can
harness it.
5. In every transfer of energy, some portion escapes. The degree to which
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we successfully capture energy is termed the energy conversion
efficiency and is the ratio of useful output of energy to the amount that
needs to be input.
C. Light energy from the sun powers most living systems.
1. Some organisms use the sun’s radiation to produce their own food.
Such organisms are called autotrophs or primary producers and
include green plants, algae, and cyanobacteria.
2. Autotrophs turn light energy from the sun into chemical energy in a
process called photosynthesis. In photosynthesis, sunlight powers a
series of chemical reactions that converts water and carbon dioxide
into sugars and oxygen, transforming diffuse energy from the sun into
concentrated energy the organism can use.
D. Photosynthesis produces food for plants and animals
1. In a series of chemical reactions called light reactions, photosynthesis
uses solar energy to split water molecules to form hydrogen ions and
the oxygen we breathe.
2. The light reactions produce energy molecules that fuel reactions in the
Calvin cycle where sugars are formed.
3. The net process of photosynthesis is defined by the chemical equation:
6CO2 + 6H2O + the sun’s energy → C6H1206 (sugar) + 6O2
4. Animals depend on the sugars and oxygen from photosynthesis.
E. Cellular respiration releases chemical energy.
1. Organisms make use of the chemical energy created by photosynthesis
in a process called cellular respiration, which is vital to life.
2. Cells employ oxygen to convert glucose back into its original starting
materials, water and carbon dioxide, and release energy to form
chemical bonds or perform other tasks within cells.
3. The net equation for cellular respiration is the exact opposite of that
for photosynthesis:
C6H12O6 (sugar) + 6O2 → 6CO2 + 6H2O + energy
4. The energy released per glucose molecule in respiration is only twothirds of the energy input per glucose molecule in photosynthesis, an
example of the second law of thermodynamics.
5. Cellular respiration occurs in all living things and in both the
autotrophs that create glucose and in heterotrophs, or consumers.
F. Geothermal energy also powers Earth’s systems.
1. A minor energy source is the gravitational pull of the moon, which, in
conjunction with the sun, causes ocean tides.
2. A more significant additional energy source is the geothermal heating
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emanating from inside the earth, powered primarily by radiation from
radioisotopes deep inside our planet.
3. Hydrothermal vents are areas in the deep ocean from which jets of
geothermally heated water emerge. Hydrothermal vent communities
utilize chemical energy instead of light energy.
4. Communities of living organisms at these locations depend on bacteria
at the base of the food web; these bacteria fuel themselves by
chemosynthesis using the chemical bond energy of hydrogen sulfide:
6CO2 + 6H2O + 3 H2S → C6H12O6 (sugar) + 3H2SO4
IV.
Geology: The Physical Basis for Environmental Science
1. A good place to begin understanding how our planet functions is right
beneath our feet: rocks, soil, and sediments.
2. Our planet is dynamic and this dynamism is what motivates geology,
the study of Earth’s physical features, processes and history. Two
geological processes of fundamental importance are plate tectonics
and the rock cycle.
A. Earth consists of layers.
1. Most geological processes take place near the Earth’s surface.
2. Earth’s center is a dense core consisting mostly of iron, solid in the
inner core and molten in the outer core.
3. Surrounding the core is a less dense, elastic layer called the mantle. A
portion of the upper mantle is the asthenosphere, which contains soft
rock. Above that is the harder rock we know as the lithosphere.
4. The lithosphere includes the Earth’s crust, the thin layer of rock that
covers the surface.
5. The heat from inner Earth rises to the surface and dissipates. Where
the asthenosphere approaches within a few miles of the surface, we
can drill to tap geothermal energy. But the soil and rock just below the
Earth’s surface is fairly constant in temperature, (cooler than the air in
summer and warmer than the air in winter), allowing homes to use
geothermal energy efficiently.
6. The heat from the inner layers of the Earth also drives convection
currents that move mantle material. As this material moves it drags
lithospheric plates along the surface. This movement is known as
plate tectonics.
B. Plate tectonics shape Earth’s geography.
1. Our planet’s surface consists of about 15 major tectonic plates which
move at rates of roughly 2 to 15 cm per year.
2. The plates’ movement has influenced Earth’s climate and life’s evolution.
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C. There are three types of plate boundaries.
1. At divergent plate boundaries, tectonic plates push apart as magma
rises upward to the surface, creating new crust as it cools. An example
is the Mid-Atlantic ridge.
2. Where two plates meet, they may slip and grind alongside one another,
forming a transform plate boundary or a fault. The San Andreas
Fault in California is an example of this type of boundary.
3. When plates collide at convergent plate boundaries, two scenarios
are possible. One plate may slide beneath the other in a process called
subduction. This can lead to volcanic eruptions. The Cascades in the
Pacific Northwest are an example and led to the eruption of Mount
Saint Helens in 1980 and 2004. When two plates of continental
lithosphere meet, the continental crust on both sides resists subduction
and instead crushes together, bending, buckling, and deforming layers
of rock from both plates in a continental collision. The Himalayas
were formed in this manner and continue to be uplifted.
D. Tectonics produce Earth’s landforms.
1. The Geysers in California are located above a region of subduction,
which is why magma rises to the surface.
2. Tectonic processes shape climate and life’s evolution by changing
areas of coastal regions to continental interiors and the reverse.
E. The rock cycle alters rock.
1. Over geological time, rocks and the minerals that comprise them are
heated, melted, cooled, broken down, and reassembled in a very slow
process called the rock cycle.
2. A rock is any solid aggregation of minerals. A mineral is any
naturally occurring solid element of inorganic compound with a
crystal structure, a specific chemical composition, and distinct
physical properties.
F. Igneous rock
1. If magma is released through the lithosphere, it may flow or splatter
across Earth’s surface as lava. Rock that forms when lava cools is
called igneous rock.
2. There are two main classes of igneous rock. Intrusive igneous rock
forms when magma cools slowly and solidifies while it is below the
Earth’s surface, giving rise to rocks with large crystals such as granite.
The second class is formed when molten rock is ejected from a
volcano and cools quickly. This class is called extrusive igneous rock
and its most common representative is basalt.
G. Sedimentary rock
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1. Through weathering, particles of rock blown by wind or washed away
by water come to rest downhill, downstream, or downwind from their
sources, eventually forming sediments.
2. Sediments can also form chemically from the precipitation of
substances out of solution.
3. Sedimentary rock is formed as sediments are physically pressed
together; dissolved minerals bind the particles together in a process
known as lithification. Sandstone, shale, and limestone are examples
of sedimentary rock.
4. These processes also create the fossils of organisms and the fossil
fuels we use for energy.
H. Metamorphic rock
1. When any type of rock is subjected to great heat and pressure, such as
from geologic forces deep underground, it may alter its form,
becoming metamorphic rock. Metamorphic rock includes slate and
marble.
V.
Geologic and Natural Hazards
1. Earth’s geothermal heating gives rise to creative forces that shape our
planet. They can include hazards such as earthquakes and volcanoes.
2. Nine out of ten of the world’s earthquakes and over half of the world’s
volcanoes occur on plate boundaries that are on the circum-Pacific
belt, the so-called “ring of fire.”
A. Earthquakes result from movement at plate boundaries and faults.
1. Plate boundaries and other places where faults occur may relieve builtup pressure in fits and starts. Each release of energy causes what we
know as an earthquake.
2. Damage from earthquakes is generally greatest where soils are loose
or saturated with water.
3. Engineers have developed ways to protect buildings from earthquakes
and such designs are an important part of new building codes in
earthquake-prone areas such as California and Japan.
B. Volcanoes arise from rifts, subduction zones, or hotspots.
1. Where molten rock, hot gas, or ash erupt through the Earth’s surface, a
volcano is formed, often creating a mountain over time as cooled lava
accumulates.
2. At some volcanoes, such as Mount Kilauea in Hawaii, lava flows
continuously downhill. At others, a volcano may let loose large
amount of ahs and cinder in a sudden explosion, such as during Mount
Saint Helen’s 1980 eruption.
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3. Volcanic eruptions exert environmental impacts. Large eruptions can
depress temperatures throughout the world as a result of ash blocking
sunlight and sulfuric acid hazes that block radiation and cool the
atmosphere.
C. Landslides are a form of mass wasting.
1. A landslide occurs when large amounts of rock or soil collapse and flow
downhill. Landslides are a severe and sudden manifestation of mass
wasting, the downslope movement of soil and rock due to gravity.
2. Mass wasting can be brought about by human land practices that
expose or loosen soil. Mass wasting events can be colossal and deadly,
such as the mudslides that occur after torrential hurricane rainfall or
following volcanic eruptions.
D. Tsunamis can follow earthquakes, volcanoes, or landslides.
1. Earthquakes, volcanic eruptions, and large coastal landslides can all
displace huge volumes of ocean water instantaneously and trigger a
tsunami, an immense swell or wave of water that can travel thousands
of miles across oceans.
2. Residents of the United States are vulnerable to tsunamis as well. A
Canary Island volcano could put Atlantic-coast cities at risk.
E. We can worsen or mitigate the impacts of natural hazards.
1. Flooding, coastal erosion, wildfire, tornadoes, and hurricanes are “natural
hazards” whose impacts can be worsened by the choices that we make.
a. As the population grows, more people live in areas susceptible to
disaster, sometimes by choice.
b. We use and engineer landscapes in ways that can increase the
severity of natural hazards.
c. As we change Earth’s climate by emitting greenhouse gases, we
alter patterns of precipitation, increasing risks of drought, flooding
and fire. Rising sea levels increase coastal erosion.
2. We can reduce the impacts of hazards through the thoughtful use of
technology and a solid understanding of geology and ecology.
VI.
Conclusion
A. Geothermal heating provides one window into the broad phenomena of
chemical and physical processes that shape our planet.
B. An understanding of matter and energy is essential for all science and
particularly for finding solutions to environmental problems.
C. The physical processes of geology are important because they shape Earth’s
terrain and generate phenomena that can threaten our lives and property.
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Key Terms
acidic
atoms
autotrophs
basic
carbohydrates
carbon
carbon dioxide
cellular respiration
chemistry
chemosynthesis
compound
continental collisions
convergent plate boundary
core
crust
deoxyribonucleic acid (DNA)
divergent plate boundary
earthquake
electrons
element
energy
first law of thermodynamics
genes
geology
geothermal energy
half-life
heterotrophs
hydrocarbons
hydrogen
hydrothermal vents
igneous rock
ions
isotopes
kinetic energy
landslide
lava
law of conservation of matter
lithosphere
macromolecules
magma
mantle
mass wasting
matter
metamorphic rock
methane
mineral
molecules
neutrons
nitrogen
nucleic acids
organic compounds
oxygen
ozone
pH
photosynthesis
plastics
plate tectonics
polymers
potential energy
primary producers
proteins
protons
radioactive
ribonucleic acid (RNA)
rock
rock cycle
second law of thermodynamics
sedimentary rock
sediments
silicon
subduction
transform plate boundary
tsunami
volcano
water
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Teaching Tips
1. Ask students to generate a list of environmental problems and write them on the
board. As a group, analyze each problem to determine how chemistry is
involved in understanding it. For example, smog is the result of the chemical
reaction of nitrogen oxides and hydrocarbons in the presence of sunlight. Allow
students to use the textbook if they need more information.
2. Ask students to consider the ways in which they utilize kinetic energy each day.
Then ask them to describe the potential energy source that was converted.
3. Ask students to describe what the consequences to the environment would be if
water did not become less dense upon freezing.
4. The recent fire and explosion on an oil drilling rig in the Gulf of Mexico, and
the subsequent leakage of oil into the environment, has had far-reaching
consequences. Ask students to search the Internet for information on the fate of
various components of the crude oil, i.e., how the molecular weight of the
hydrocarbons affected the deposition, transport, and treatment of components.
Examine the issue that arose with methane hydrates during the attempt to stop
the flow. Ask students to compare this situation with that of the Exxon Valdez
oil spill in Prince William Sound. A current and reliable Web page is the
NOAA’s Office of Response and Restoration, “Prince William Sound: An
Ecosystem in Transition” (http://response.restoration.noaa.gov/bat/about.html).
5. Lead a discussion of why perpetual motion machines are impossible and show
some examples of ones that have been proposed and the fallacious reasoning on
which they are based. Extensive resources exist on the Internet for this.
6. In this chapter, DNA and RNA are described. Recent scientific research on
DNA has centered on genetic engineering and cloning. Lead a discussion about
the pros and cons of these issues.
7. The ecological footprint exercise in this chapter leads into a more complex
discussion in later chapters. Explore with the students why energy
considerations might be important in this regard while also keeping in mind the
first and second laws of thermodynamics.
8. Community Service. Have the students explore potential natural hazards in their
communities. Is there sufficient information being provided to residents regarding these?
Could students propose ways to improve the dissemination of such information?
Additional Resources
Websites
1. Office of Response and Restoration, Oceanic Service, NOAA
(http://response.restoration.noaa.gov)
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This website is the gateway to the NOAA department that is involved in
oceanic environmental disasters, including the Exxon Valdez oil spill in Prince
William Sound.
2. General Chemistry Online!, Frostburg State University
(http://antoine.frostburg.edu/chem/senese/101/index.shtml)
This Web resource is an interactive guide for students and teachers of
introductory college chemistry.
3. Life on Mars?, NASA (http://nssdc.gsfc.nasa.gov/planetary/marslife.html)
This NASA Web resource describes the ALH84001 meteorite that was found to
contain organic molecules and mineral features indicative of primitive life on Mars.
4. Vents Program, Pacific Marine Environmental Laboratory, NOAA
(www.pmel.noaa.gov/vents)
The Vents Program website provides information about submarine volcanoes
and hydrothermal venting.
5. Encyclopedia of Earth, Environmental Information (http://www.eoearth.org/)
An electronic reference about the Earth, its natural environments, and their
interaction with society. The Encyclopedia is a free, fully searchable collection
of articles written by scholars, professionals, educators, and experts who
collaborate and review each other's work.
6. NOAA Watch, NOAA’s All Hazard Monitor (http://www.noaawatch.gov/)
As the title implies, this is a website that provides current information on all
natural hazards worldwide, including earthquakes, volcanoes, severe weather
and drought.
7. Latest Earthquakes in the World, United States Geological Survey,
(http://earthquake.usgs.gov/earthquakes/recenteqsww/)
This website is a wonderful online resource for the classroom providing visual
data on the latest earthquakes worldwide. It is capable of zooming in to very
local areas. Like the previous item, the parent site also has a lot of visual
information on the larger class of natural hazards.
Audiovisual Materials
1. Origins, 2004, NOVA, produced by Thomas Levenson and distributed by PBS
(www.shop.pbs.org)
Neil deGrasse Tyson narrates this four-part series that explores the origins of
the universe, the Earth, and life. The program is available in VHS and DVD
formats and comes with a companion book.
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2. Volcanoes of the Deep Sea, 2003, produced by Stephen Low and distributed by
Discovery Channel (http://shopping.discovery.com)
This 90-minute film accompanies a team of scientists to an incredible world
teeming with life 12,000 feet beneath the ocean surface. This prize-winning
documentary was originally created for exhibition in IMAX theaters and is
available on only DVD.
3. Natural Hazards Video Gallery United States Geological Survey
(http://gallery.usgs.gov/video_collections/Natural_Hazards)
This is a very large collection of short video clips on a wide range of
natural disasters.
Weighing the Issues: Facts to Consider
Your Risk from Natural Hazards
Facts to consider: Two very useful websites for beginning this discussion are:
http://earthobservatory.nasa.gov/NaturalHazards/category.php?cat_id=9
and
http://map.ngdc.noaa.gov/website/seg/hazards/viewer.htm
You can find information on nearly every possible natural hazard for locations
throughout the world on these two websites. The importance of science in the
decision of rebuilding is often diminished by cultural and economic considerations.
The Science behind the Stories:
Thinking Like a Scientist
Mapping the Unknown Beneath Us
Observation: We know comparatively little about what goes on beneath the
Earth’s surface yet these processes affect us all.
Application: A large consortium of researchers are attempting to map the
lithosphere beneath the entire United States. A 15-year program will place a
moving array of seismometers across the country. Longitudinal bands of
seismometers will stretch from the Pacific coast to the Atlantic coast in a phase of
the project to be completed in 2013. By recording the seismic waves from
earthquakes or other sources of vibrations, researchers can not only determine the
location and magnitude of earthquakes but can also infer the underground structure
of rock layers. By doing this research, scientists hope to better understand
earthquakes, and perhaps one day be able to predict when they will occur.
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Have We Brought on a New Geologic Epoch?
Question: Have the impacts of human beings on Earth been so profound as to
warrant creating a new time period in the geologic record?
Arguments: Geologists have divided the span of Earth’s history, 4.5 billion years
of it, into three eras and 11 periods. Periods are subdivided into epochs. We live in
the Holocene epoch, defined by the stable climate period commencing with the
warming trend that ended the last ice age, about 11,500 years ago. Some scientists
have argued that human beings have ushered in a new phase of the geologic record
by causing a sharp increase in soil erosion and by the emission of greenhouse gases
causing rising temperatures and rising sea levels. Atmospheric carbon dioxide is
acidifying the oceans and causing changes in coral reefs and geological strata.
Supporters of a new time period maintain that these changes will be readily visible in
the future stratigraphy and that we should recognize this with a new epoch called the
Anthropocene. Other scientists question whether the proposal upholds the tradition of
defining time periods based on what is actually seen in the scientific record.
Answers to End-of-Chapter Questions
Testing Your Comprehension
1. Atoms are the basic building blocks of matter. The differing number of protons
in each atom distinguishes them as different elements. Oxygen, silicon, and
nitrogen are common in the Earth’s physical systems. In living organisms, the
elements carbon, hydrogen, oxygen, nitrogen, and phosphorus are most common.
2. An ion is an electrically charged atom or combination of atoms, an entity that
has gained or lost electronics. An isotope is an atom of the same element with a
differing number of neutrons. An atom is a single structure consisting of a
nucleus containing protons and neutrons and surrounded by electrons. A
molecule is a chemical combination of two or more atoms. A compound is a
molecule composed of atoms of two or more different elements.
3. Potential energy, or energy of position, is a form of energy storage. This energy
may be released as kinetic energy, or energy of motion, when the object falls and is
accelerated by the force of gravity. When water evaporates and rises into a cloud, it
gains considerable potential energy. When that water falls to the ground and runs
downstream in a river, its potential energy is converted to kinetic energy.
4. The total amount of energy in the universe is constant and is conserved.
Therefore, when energy is converted from one form to another, it should be
possible to account for all of the energy in one form or another. The second law
of thermodynamics states that the nature of energy will change from a moreordered to a less-ordered state as long as no force counteracts this tendency.
When energy is converted from one form to another, some of it is converted
into a less useful form and is effectively lost to us.
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5. Sunlight (which drives photosynthesis), geothermal energy (from radiation deep
below ground), and the gravitational pull of the moon power Earth’s
environmental systems.
6. Photosynthesis produces oxygen molecules and sugar; aerobic cellular
respiration produces carbon dioxide, water, and energy; and chemosynthesis
produces sugar, oxygen, and sulfates.
7. The primary layers of the planet are the core, the mantle, and the crust. The
lithosphere includes the uppermost portion of the mantle and the entirety of
the crust.
8. Tectonic plates push apart at a divergent plate boundary allowing magma to rise
upward creating new crust. At a transform plate boundary, two plates slip and
grind alongside one another. Convergent plate boundaries can exhibit either
subduction, where one plate slides beneath the other, or a continental collision
where both plates are uplifted. Both cases can cause earthquakes and create
mountains, but the former is the source of most volcanism.
9. Igneous, sedimentary, and metamorphic are the three main types of rock. All
rock can be reassembled over time by the rock cycle and can be the source of
each type. Igneous rock results from the melting of rock deep beneath the
surface of the Earth and its release in a molten state through the lithosphere in a
volcanic eruption or at a divergent plate boundary. Sedimentary rock results
from the weathering of rock by wind or water and its deposition downwind or
downstream. Metamorphic rock results from rock being subjected to great heat
and pressure at temperatures below its melting point but high enough to change
its appearance and physical properties.
10. At plate boundaries, pressure is built up and relieved in fits and starts. Each
release of energy causes an earthquake. Tsunamis are an immense swell, or
wave, of water that occurs when huge volumes of ocean water are displaced by
earthquakes, volcanic eruptions, or coastal landslides. Mount Kilauea exhibits a
slow, constant flow of lava downhill to the sea while Mount Saint Helens
released an enormous amount of ash and cinder in a sudden explosion.
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Calculating Ecological Footprints
Diet
Source
of
calories
Number of calories
consumed
Ecologically
equivalent
calories
Total ecologically
equivalent calories
100% plant
0% animal
90% plant
10% animal
50% plant
50% animal
0% plant
100% animal
Plant
2,000
2,000
2,000
Animal
0
0
Plant
90% × 2,000 = 1,800
1,800
1,800 + 2,000 = 3,800
Animal
200
×
10
=
2,000
200
Plant
1,000
1,000
11,000
Animal
1,000
1,0000
Plant
0
0
20,000
Animal
2,000
20,000
1. Multiply the total ecologically equivalent calories per day by 365 days per year:
730,000 calories; 1,387,000 calories; 4,015,000 calories; and 7,300,000
calories, respectively.
2. A diet of only animal food has 10 times the ecological impact of a strictly
vegetarian diet (20,000 ecologically equivalent calories per day vs. 2,000).
Taking just 10% of one’s diet from animal sources means consuming an
additional 1,800 ecologically equivalent calories beyond those of a strictly
vegetarian diet.
3. Answers will vary.
4. The combined ecological impact of feeding so many people at the inefficient
upper end of the food chain may exceed Earth’s capacity. Large predators are
usually rare. We would be the only exception, if we choose to be predators
(carnivores), but we should be aware that we cannot violate the second law of
thermodynamics.
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