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the portion of the earth's crust that primarily contains granite, is less dense than oceanic crust, and is 20-50 km thick
The portion of Earth's crust that is usually below the oceans, thinner and higher in density than continental crust and made of basalt
Continental Drift Theory
Alfred Wegner, 1915, theory that states that the gradual shifting of Earth's plates causes continents to change their global positions over time
Seafloor Spreading Theory
dating of the rocks indicated that farther away from the ridge, the rocks became older, the crust was created at volcanic rift zones
areas on the earth where two tectonic plates move and meet towards each other, one sliding underneath the other and moving down into the mantle .
Plates slide apart from the othere with the space that was created being filled with molten magma from below (ie East African Great Rift Valley)
Plates slide toward each other forming either a subduction zone or an orogonic belt (ie Cascade Mountain Range)
Two oceanic plates converge-->
they create an island arc, curved chain of volcanic islands rising from the deep seafloor and near a continent. (ie Aleutian Islands by Alaska)
Two continental plates collide-->
mountain ranges are created as the colliding crust is compressed and pushed upwards (ie Himalayas)
a logarithmic scale of 1 to 10 used to express the energy released by an earthquake recorded by a seismograph, compares amplitudes of waves on a seismograph really
body waves that are produced when material moves either vertically or horizontally and travel only within the uppermost layers of earth
Severity of an earthquake depends on...
1.) the amount of potential energy that has been stored
2.) the distance the rock mass moved when the energy was released
3.) how far below the surface the movement occurred
4.) the makeup of the rock material
series of waves created when a body of water is rapidly displaced usually by an earthquake, can be devastating, subduction-zone related earthquakes lead to most tsunamis, rarely form near divergent boundaries, small wave height offshore, long wavelength, pass unnoticed at sea
classified as: intermittent, dormant, or extinct; most occur at subduction zones and mid-oceanic ridges, others occur at hot spots (areas of plumes of magma come close to the surface), volcanoes release sulfur dioxide, hydrogen chloride, carbon dioxide, and steam; eruption's particles increases average temperature and contributes to acid rain
occur when pressure within a magma chamber forces molten magma through a conduit pope and out a vent at the top of the volcano, correlation exists between seismic and volcanic activity
Factors that affect solar energy at Earth's surface
Earth's rotation, tilt of Earth's axis, and atmospheric conditions
Surface Litter: leaves and partially decomposed organic debris, may be very thick in deciduous forests and very thin in tundra and desert
Topsoil: Organic Matter (humus), living organisms, inorganic minerals. the topsoil is typically very thick in grasslands
Subsoil: tends to be yellowish in color due to the accumulation of iron, aluminum, humic compounds, and clay leached down from the A and E horizons, can be rich in nutrients in areas where rainwater leeched nutrients from the topsoil
very fine particles, compacts easily, forms large, dense clumps when wet, low permeability to water; therefore, upper layers become waterlogged
about equal mixtures of clay, sand, silt, and humus, rich in nutrients, holds water but does not become waterlogged
sedimentary material coarser than silt, water flows through too quickly for most crops, good for crops and plants requiring low amounts of water
sedimentary material consisting of very fine particles between the size of sand and clay, easily transported by water
Soil Food Web
First trophic level: photosynthesizers
Second trophic level: decomposers, mutualists, pathogens, parasites, root-feeders
Third trophic level: shredders, predators, grazers
Fourth trophic level: higher level predators
Fifth and higher: higher level predators
three common forms: animal manure, green manure, and compost; improves water-holding capacity of soil; helps to prevent erosion
Does not add humus to the soil, resulting in less ability to hold water and support living organisms (earthworms, beneficial bacteria, and fungi)
Lovers oxygen content of soil thereby keeping fertilizer from being taken up efficiently
Supplies only a limited number of nutrients (usually nitrogen and phosphorous)
Requires large amounts of energy to produce, transport and apply
Releases nitrous oxide--a green house gas
Causes of soil erosion
flowing water, wind, and human activity (cultivating inappropriate land, burning of native vegetation, deforestation, and construction)
Poor agricultural techniques
monoculture, row cropping, overgrazing, improper plowing of the soil, and removing crop wastes instead of plowing the organic material back to the soil
Soil erosion damages...
agriculture, waterways (canals), and infrastructures (dams), wetland ecosystems, reproductive cycles (salmon), oxygen capacity, and pH of water
productive potential of arid or semiarid land falls by at least 10% due to human activity and/or climate change
Water that is not absorbed into the soil and evaporates leaves behind dissolved salts in topsoil
masses of rock, earth, or debris move down a slope; also known as debris flows; landslides are caused by the turbances in the natural stability of a slope, occur after droughts, earthquakes, or volcanic eruptions,
rocks solidify on or near the surface, cool quickly and have a fine-grained smooth texture (basalt)
formed by intense heat and pressure
High quartz content --> sandy soil
Slate --> silt soil
Marble --> limestone clay
Common examples: diamond, marble, asbestos, slate anthracite coal
formed by poling and cementing of various materials (diatoms, weathered chemical precipitates, fragments of older rocks) over time in a low-lying area, fossils only form in this
1935 Soil Erosion Act
established the soil conservation service, mandates the protection of the nation's soil reserves, deals with soil erosion problems, carries out soil surveys, and does research on soil salinity, provides computer databases for scientific research
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