APES Unit 4

Earth Sturctures

  • Core: Dense mass of solid nickel, iron, and radioactive elements that release massive amount of heat

  • Mantle: liquid layer of magma surrounding core, kept liquefied by intense heat from core

  • Asthenosphere: solid, flexible outer layer of mantle, beneath the lithosphere

  • Lithosphere: thin, brittle layer of rock floating on top of mantle (broken up into tectonic plates)

  • Crust: very outer layer of the lithosphere, earth’s surface

Convention Cycles

  • Magma heated by earth’s core rises towards lithosphere

  • Rising magma cools & expands, forcing oceanic plates apart

    • Creates, mid ocean ridges, volcanoes, spreading zones or “seafloor spreading”

  • Magma cools, and solidifies into new lithosphere

    Spreading magma forces oceanic plate into cont. (subduction zone)

    • Sinking oceanic plate melts back into magma

    • Also forces magma up, creating narrow, coastal Mtns. (Andes) & volcanoes on land

Plate Boundaries

Divergent Plate Boundary

  • Plates move away from each other

  • Rising magma from mantle forces plates apart

    • Forms: mid-oceanic ridges, volcanoes, seafloor spreading, and rift valleys (on land)

Convergent Plate Boundary

  • Plates move towards each other 

  • Leads to subduction (one plate being forced beneath another)

    • Forms: mountains, island arcs, earthquakes, and volcanoes

Transform Fault Plate Bound

ary

  • Plates slide past each other in opposite directions

    • Forms: earthquakes

Convergent Boundary =  Subduction Zone

Oceanic-Oceanic : one plate subducts underneath other

  • Forces magma up to lithosphere surface, forming mid ocean volcanoes

    • Island arcs

  • Off-shore trench 


Oceanic-Continental : dense oceanic plate subducts beneath cont. Plate & melts back into magma

  • Forces magma up to lithosphere surface

  • Coastal Mountains (Andes), Volcanoes on land, trenches, tsunamis


Continental-Continental one plate subducts underneath other, forcing surface crust upward (mountains)

  • Ex: Himalayas


Transform Fault Boundary

  • Plates sliding past each other in opp. directions creates a fault (fracture in rock surface)

    • Earthquakes = most common activity

    • Occurs when rough edges of plates get stuck on each other

    • Pressure builds as plates keep sliding, but edges stay stuck

    • When stress overcomes the locked fault, plates suddenly release, slide past each other and release energy that shakes the lithosphere


Tectonic Map Can Predict...

Ring of Fire: pattern of volcanoes all around pacific plate

  • Offshore island arcs (Japan) 

Transform faults: likely location of earthquakes

Hotspots: areas of esp. hot magma rising up to lithosphere

  • Mid-ocean Islands (iceland, Hawaii)   


SOIL FORMATION AND EROSION

Plants: anchors roots of plants and provides water, shelter, nutrients (N, P, K, Mg) for growth


Water: filters rainwater + runoff by trapping pollutants in pore spaces + plant roots. Clean water enters groundwater + aquifers


Nutrient Recycling: home to decomposers that break down dead organic matter + return nutrients to the soil

Habitat: provides habitat for org. like earthworms, fungi, bacteria, moles, slugs

What is Soil?

Mix of geologic (rock) and organic (living) components

  • Sand, silt, clay

  • Humus: main organic part of soil (broken down biomass like leaves, dead animals, waste, etc.)

  • Nutrients: ammonium, phosphates, nitrates

  • Water and Air

  • Living Organisms

Weathering

  • Breakdown of rocks into smaller pieces

    • Physical (wind, rain, freezing/thawing of ice)

    • Biological (roots of trees crack rocks)

    • Chemical (acid rain, acids from moss/lichen)

  • Weathering of rocks = soil formation

    • Broken into smaller and smaller pieces

    • Carried away and deposited by erosion

Erosion

  • Transport of weathered rock fragments by wind and rain

  • Carried to new location and deposited (deposition)

Soil Formation

  • From below

    • Weathering of parent material produces smaller, and smaller fragments that make up geological/inorganic part of soil

      • Sand, silt, clay

      • Minerals

  • From above

    • Breakdown of organic matter adds humus to soil

    • Erosion deposits soil particles from other areas, adding to soil

Effects on Soil Form.

Parent material: soil pH, nutrient content 


Topography: steep slope = too much erosion; 

more level ground = deposition


Climate: warmer = faster breakdown of org. matter; 

more precip. = more weathering,  erosion + deposition


Organisms: Soil organisms like bacteria, fungi, worms breakdown organic matter

Soil Horizons

O-Horizon: layer of organic matter (plant roots, dead leaves, animal waste, etc) on top of soil

  • Provides nutrients and limits H2O loss to evap.

A-Horizon: aka topsoil; layer of humus (decomposed organic matter) and minerals from parent material

  • A-Horizon has most biological activity (earthworms, soil microbes) breaking down organic matter to release nutrients

B-Horizon: aka subsoil; lighter layer below topsoil, mostly made of minerals w/little to no org. matter

  • Contains some nutrients

C-Horizon: least weathered soil that is closest to the parent material, sometimes called bedrock

Soil Degradation: The loss of the ability of soil to support plant growth

Loss of Topsoil: tiling (turning soil for ag.) + loss of vegetation disturb soil and make it more easily eroded by wind and rain

  • Loss of top soil dries out soil, removes nutrients + soil organisms that recycle nutrients


Compaction: compression of soil by machines (tractors, bulldozers, etc.), grazing livestock, and humans reduces ability to hold moisture

  • Dry soil erodes more easily

  • Dry soil supports less plant growth, less root structure, leading to more erosion

Nutrient Depletion: repeatedly growing crops on the same soil removes key nutrients (N, P, K, Na, Mg) over time

  • Reduces ability to grow future crops

    Soil Particle Size, Texture, and Porosity

    • Geologic (rock) portion of soil is made up of 3 particles

      • (biggest to smallest) Sand > silt > clay

    • Soil Texture: is the % of sand, silt, and clay in a soil

      • Always adds up to 100% ex: 40-40-20

    • B/c sand is bigger, it has bigger pores (empty spaces between particles)

      • This allows air + water to enter sandy soil easily

      • Clay has smallest pores, so it’s harder for air + water to enter clay-heavy soils

    • Porosity is the amount of pore space a soil has

      • more sand in a soil = more porous/higher porosity (easier for water + air to enter)

      • more clay in a soil = less porous/less porosity (harder for water + air to enter)

    Porosity, permeability, and H2O Holding Capacity

    • Porosity: the pore space within a soil (more sand, more porous)

    • Permeability: how easily water drains through a soil

    • More porous/higher porosity = more permeable/higher permeability

      • Positive relationship between porosity + permeability

    • H2O holding Capacity: how well water is retained, or held by a soil

      • More porous/permeable = lower H2O holding capacity

Inverse relationship between porosity/permeability and H2O holding capacity

Effect on Soil Fertility


Soil that is too sandy (too permeable) drains water too quickly for roots + dries out


Clay-heavy soil doesn’t let H2O drain to roots, or waterlogs (suffocating them) 


Ideal soil for most plant growth is loam, which balances porosity or drainage, with H2O holding cap.

Soil Fertility: ability of soil to support plant growth

Nutrients

  • N, P, K+, Mg2+, Ca+, Na+

  • Factors that increase soil nutrients

    • Organic matter (releases nutrients)

    • Humus (holds and releases nutrients)

    • Decomposer activity (recycles nut.)

    • Clay (neg. charge binds pos. nutrients)

    • Bases (Calcium carbonate - limestone)

  • Factors that decrease soil nutrients

    • Acids leach pos. charge nutrients 

    • Excessive rain/irr. leeches nutrients

    • Excessive farming depletes nut.

    • Topsoil erosion

      Water

      • Needs to hold water, but not too much

      • Factors that increase H2O holding cap.

        • Aerated soil (biological activity)

        • Compost/humus/organic matter

        • Clay content

        • Root structure, especially natives

      • Factors that decrease H2O holding cap.

        • Compacted soil (machines, cows)

        • Topsoil erosion

        • Sand

        • Root loss