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EARTH 109 Final: earth final review (i got an A-).docx

Earth and Environmental Sciences
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Study Guide

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1. Introduction: Water in our planet, main water reservoirs, Brief overview of some of the main water issues we are
facing today, Placing the water reservoirs into the earth's context
70% of the earth’s surface is covered by water
conclusion: most of the water in and at the surface of earth is not usable by humans
usable/potable water by humans: groundwater 0.61%, freshwater lakes 0.009%, rivers 0.0001%
total usable water accounts only for 0.62% of the total water present in and on the earth
groundwater represents 98% of all available water for human consumption
in order to preserve and protect this scarce resource, one has to 1) evaluate both surface and groundwater
resources in different areas; and 2) to properly manage these resources by establishing limits on the amounts to
be used and by protecting it from being exposed to contaminants.
These steps have to be taken for every region.
When these limits are not respected, problems arise… 1) coastal areas: problems with sea water intrusion; 2)
continental areas: problems with land subsidence; 3) other issues such ahs dealing with disposal of radioactive
waste at depth, which risk groundwater contamination, also other general groundwater and surface water
contamination problems eg potential groundwater contamination due to hydraulic fracturing of shales to extract
natural gas, contamination released to surface water, including fecal coliforms, pesticides, pharmaceuticals, etc
Nuclear energy: water and rock cycles
oA dynamic earth: sun = huge natural nuclear reactor operating by FUSION. Energy produced by the Sun
(through fusion) powers the hydrological cycle

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oNuclear energy is produced naturally in the sun and many other stars through fusion; in the earth’s
interior (crust and mantle) through fission and radioactive decay (that is how heat is produced)
oFusion, fission + radioactive decay all produce nuclear energy
oFusion: two atoms of hydrogen joined together or fuse to create a larger atom, helium; energy is released
in the process in the form of heat
oFission: splitting of an atom into smaller ones. Energy is released and the sum of the masses of the
fission products is smaller than the original mass; fission is accomplished when a big atom such as
Uranium is bombarded by neutrons
oRadioactive decay: radioactive materials undergo a process of spontaneous decay, in which big atoms or
nuclides disintegrate to form other atoms that maybe, in turn, also unstable, and thus will also decay. The
decaying process will go on until a stable nuclide is finally formed. It is through radioactive decay of
different elements that most of the noble gases (helium for example) and heat are produced in the earth.
oThe nuclear energy produced in the earth’s interior (due to fission and r. decay) aka geothermal energy,
powers the rock/lithospheric cycle.
rock cycle

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odensity of lithosphere < “plastic mantle”s density= lithosphere floats on top of “plastic mantle” (isostasy)
oearth’s radius 6370km. core temp 6000celsius.
oHeat transfer to earth’s surface: 1) convection (“plastic mantle”): presence of convective cells 2)
conduction (lithosphere): very slow process where thermal energy is passed from one atom to another
oPlate tectonics: because the lithosphere is a thin cold brittle material floating and moving on top of the
ductile mantle it breaks into several segments aka tectonic plates (7 major: N&S Am, African, Eurasian,
Indian-Australian, Pacific, Antarctic Plate)
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