Intro to Natural Disasters-III

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  • 8/11/2019 Intro to Natural Disasters-III

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  • 8/11/2019 Intro to Natural Disasters-III

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    9/3/2014 Intro to Natural Disasters-III

    http://classes.geology.illinois.edu/14FallClass/geo118/Lectures/3-Intro_Nat_Disasters-III.html

    drives moving tectonic plates + associated EQ's, volcanic eruptions, + mountain uplift (> landslide hazards)

    External Energy= 1) Energy from Sun- reaches Earth as radiant (light) energy+ comprises99.98% of energy received by Earth. ~30% is immediately reflected back into space byatmosphere + oceans; ~50% is absorbed (by water + Earth), converted to heat (drivingcirculation in atmosphere + oceans), + eventually escapes back into space; 23% evaporateswater (mostly in tropics) to begin hydrologic (water) cycle. Tiny amount is absorbed by plantsduring photosynthesis + stored in plants, used by other organisms, or stored in fossil fuels like

    coal + oil.

    2) Meteorite impact energy - meteorites+ asteroidshave enormous kinetic energy (fast-moving+ can be very large), which is transferred to Earth during impact; impact generates very hightemperatures (10,000C or more) + pressures (> million atmospheres); meteorite collisions weremuch more common during early history of Earth (generated lots of heat, which is stillescaping from Earth's interior); could be considered internal heat source but ultimately derivedexternally.

    Internal (geothermal) energy= only tiny amount of energy to Earth's surface (~0.02%): 1)Radioactive Decay- Certain elements like U, Th, + K have unstable form that is radioactive,

    i.e., atoms spontaneously release subatomic particles + energy (decay) to become more stable;energy release heats rock in Earth's interior + heat slowly moves to Earth's surface.

    2) Gravity- All objects at Earth's surface (rain, snow, + earth in landslide) are continuallypulled toward Earth's center by gravity. Some of Earth's internal energy is produced bygravitational compaction of Earth's interior.

    Geologic Cycles Earth consists of different systems (components): atmosphere, hydrosphere (water),lithosphere (rock + soil), + biosphere (living organisms), which continuously interact with each otherexchanging both matter + energy on cyclical basis. These various geologic cycles play major role indevelopment of natural disasters. Examples of geologic cycles:

    Hydrologic Cycle(figure) shows movement of water through different reservoirs (locations where waterresides); main reservoirs = oceans, atmosphere (clouds), glaciers, lakes + streams, groundwater(underground water in tiny spaces in rock), + biosphere. Ocean is largest reservoir with 97% of all water.Main pathway through which water moves is atmosphere. Solar energy causes evaporation of surfacewaters + atmospheric circulation; gravity causes water to flow back to oceans (rain + snow, river, glacial, +groundwater flow).

    Chemical Cycles- Movement + reservoirs of specific elements such as carbon (+ N, P, O, S, + others) =carbon cycle(figure). 4 major reservoirs in carbon cycle = biosphere (building block of life), lithosphere (incarbonate minerals, rocks + fossil fuels, coal + oil), hydrosphere/oceans (as dissolved ions), + atmosphere

    (as carbon dioxide, CO2, gas).

    Rock Cycle(figure) - involves cycling of elements among different rock types (igneous, sedimentary, +metamorphic), so mostly involves lithosphere (but also hydrologic + chemical cycles). Geologic processesconvert one rock type to another. Energy for processes near Earth's surface = solar energy + gravity (controerosion + weathering); energy driving subsurface processes = geothermal energy + gravity (control uplift,burial, melting, + metamorphism).