APES Soil & Geology Test

4 parts of soil
– mineral particles (45%)
– organic matter (5%)
– water (25%)
– air (25%)
Why is soil important?
– shelter, food and water for microorganisms
– plants use it for nutrients and water, a place to grow
– serves as a natural filter for water
Physical Weathering
sheet erosion (wind/water peel layers of soil in sheets), rill erosion (small channels are carved out by water), gully erosion (extreme rill erosion)
Chemical Weathering
plant roots/animal cells go through cellular respiration and the CO2 diffuses into the soil, reacting with water which forms carbonic acid and this eats away at the soil/rock
Soil: texture
the amount of sand, silt and clay a soil contains; gritty (has a lot of sand), sticky (has a lot of clay), silt (smooth like flour)
Soil: friability
the ability of soil to be reduced to smaller pieces with little effort, especially by rubbing
Soil: porosity
the amount of air/water a certain volume of soil can hold
Soil: permeability
the rate at which air and water can move from upper to lower soil layers
Soil: shrink-swell potential
some soils (clay) swell when water gets in them, then crack when they dry out
Soil: pH
normal pH of soils is 4.0-8.0 (pygmy forest has acidic soil and death valley has basic soil)
Soil: slope
steep slopes have very little soil because of gravity, runoff from precipitation also erodes the soil on slopes
Soil: depth
some soils are a few inches deep until you can hit rock, others are up to 3 feet deep
Soil: color
dark soil is rich w/ lots of organic matter, light soil has very little organic matter
O-horizon
Organic Layer, uppermost layer filled with plant litter = lots of nutrients
A-horizon
Topsoil, dark/rich in organic matter and humus, granular texture and a slight loss in nutrients due to leaching of nutrients to lower levels
B-horizon
Subsoil, light colored, nutrients and minerals that have been leached accumulate here, rich in iron, aluminum and clay
C-horizon
Parent Material, weathered pieces of rock and other parent material, saturated w/ ground water
Importance of erosion
– it reduces the fertility of soil, not a good thing
– over 6 tons of soil is eroded from the US (caused by removal of plants, rising sea levels, acid rain, extreme weather due to climate change, agriculture techniques)
Methods to control erosion
1985 Food Security Act (Farm Act): called for replanting eroded land and repairing it, farmers will get a subsidy for following the law
Dangers of the Pacific Ring of Fire
the plates are spreading (divergent boundary) and moving towards each other (convergent boundary), which makes it easy for magma to come on to the surface and form volcanoes, convergent boundaries also form earthquakes when the plates get stuck on each other and then fall apart violently
Why fossils in sedimentary rock?
Sedimentary rock is formed by smaller pieces of rock and sand being pressed together. A plant or animal can be stuck inside these layers and compressed within the rock, making a fossil. Other kinds of rock are formed by heat and melting, so a fossil would not be able to remain in that kind of rock.
Sedimentary Rock
formed by layers/pieces of rock or sand being compressed together under lots of pressure (ex: conglomerate, breccia, non-clastic)
Metamorphic Rock
formed when either sedimentary or igneous rock is put under large amounts of heat and pressure, so that it turns into a different kind of rock (ex: dynamic, contact)
Igneous Rock
formed by solidified magma (ex: intrusive or extrusive)
Layers of the earth
core (solid inner core and a molten outer core), mantel or asthenosphere (molten magma), crust (tectonic plates on top of molten magma)
P waves
travel through anything, smaller and faster, compression & expansion happens horizontally
S waves
only travel through liquids, larger and slower, vertical movement
Convection Currents
inside of the mantel, heat rises and cool air/magma sinks
Convection Currents/volcanoes
saltation
when one particle hits another, increases erosion
suspension
airborne soil
surface creep
surface creeping slowly on top of the crust (a landslide is a very fast surface creep)
1985 Food Security Act
known as the Farm Act, called for replanting eroded land and repairing it, farmers will get a subsidy for following the law
leaching
dissolving minerals/matter in upper layers being carried down to lower layers
Categories: Geology