AP Environmental — Unit 4: Earth Systems and Resources

Core

Dense mass of solid nickel, iron, and radioactive elements that release massive amounts of heat

Mantle

Liuid layer of magma surrounding the core, kept liquified by intense heat from the core

Aesthenosphere

Solid, flexible outer layer of mantle beneath the lithosphere

Lithosphere

Thin, brittle layer of rock floating on the top of the mantle (broken up into tectonic plates)

Crust

Very outer layer of lithosphere, earth’s surface

Convergent Plate Boundary

• Plates move toward each other

• Leads to subduction

  • Forms mountains, islands, earthquakes, and volcanoes

Divergent Plate Boundary

• Magma heated by Earth’s core rises towards the lithosphere

• Rising magma cools and expands, forcing oceanic plates apart

  • Creates mid-ocean ridges, volcanoes, seafloor spread

• Magma cools, solidifying into new lithosphere

• Spreading magma forces the oceanic plates into continental plays

  • Sinking ocean plate melts back into the magma

  • Also forces magma up, creating narrow, coastal mountains and volcanoes on land

Transform Fault Boundary

• Plates slide past each other in the opposite direction and create a fault (fractures in rock surface)

• Creates earthquakes

• When rough edges of the plates get stuck on each other, pressure builds as the plates keep sliding but edges are stuck

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

Ring of Fire

Pattern of volcanoes all around the pacific plate

• Offshore island arcs in Japan

Hotspots

Areas of especially hot magma rising up to the lithosphere

• Mid-ocean islands like Iceland and Hawaii

Soil

• Sand, silt, clay

• Humus

• Nutrients: Ammonium, phosphates, nitrates

• Water and air

• Living organisms

Humus

The main organic part of soil with broken down biomass like leaves, dead animals, waste, etc.

Soil’s Role in Plants

Anchors the roots of plants and provides water, shelter, and nutrients for growth

Soil’s Role in Water

• Filters rainwater and runoff by trapping pollutants in pore spaces and plant roots

• Clean water enters groundwater and aquifers

Soil’s Role in Nutrient Recycling

Home to decomposers that break down dead organic matter and returns nutrients to the soil

Soil’s Role in Habitat

Provides habitat for organisms like earthworms, fungi, bacteria, moles, slugs, etc.

Soil’s Role in Weathering

Breakdown of rocks into smaller pieces

• Physical

• Biological

• Chemical

Weathering of rocks = soil formation

• Broken smaller and smaller

• Carried away and deposited by erosion

Soil’s Role in Erosion

• Transport of weathered rock fragments by wind and rain

• Carried to new location and deposited

Soil’s Role in Deposition

• Particles/pollutants/sediments settle out of the air/water and accumulates on Earth’s surface

• Originates from burning fossil fuels

• Allows for acidification of soils and water

So Formation From Below

Weathering of parent material produces smaller and smaller fragments that make geological/inorganic parts of soil

• Sand, silt, clay

• Minerals

Soil Formation From Above

• Breakdown of organic matter adds humus to soil

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

5 Soil Forming Factors

• Climate

  • Warmer = faster breakdown of organic matter adds humus

  • More precipitation = more weathering, erosion, and deposition

• Relief/Topography

  • Slope, aspect, and drainage affects water runoff, erosion, and deposition, influencing soil thickness and moisture

• Organisms

  • Soil organisms like bacteria, fungi, and worms break down organic matter

• Parent Material

  • Soil, pH, nutrient content

• Time

Soil Horizons

• O Horizon

• A Horizon

• B Horizon

• C Horizon

• R Horizon

O Horizon

Layer of organic matter (plant roots, dead leaves, animal waste) on top of soil

A Horizon

• Topsoil

• Later of humus (decomposed organic matter) and minerals from parent material

  • Has the most biological activity breaking down organic matter to release nutrients

B Horizon

• Subsoil

• Lighter layer below the topsoil, mostly made of minerals with little to no organic matter

  • Contains some nutrients

C Horizon

• Weathered parent material

• Least weathered soil that’s closest to parent material, sometimes called bedrock

R Horizon

• Bedrock

• Parent material

Soil Degradation

• The decline in soil quality, health, and productivity, making it less able to support life

• Primarily driven by human activities like poor agriculture (tilling, overgrazing, deforestation) and natural processes (erosion, salinization, nutrient depletion)

Loss of Topsoil From Tilling

• Soil Erosion & Nutrient Loss: Tilling breaks up soil structure, making the nutrient-rich topsoil easily carried away by wind and water, reducing land fertility and making it harder to grow crops.

• Water Pollution (Eutrophication): Eroded soil carries excess nutrients (nitrogen, phosphorus) and agrochemicals into rivers and lakes, causing algal blooms that deplete oxygen and harm aquatic life (eutrophication).

• Decreased Water Retention & Increased Flooding: Disturbed soil has poorer structure and organic matter, reducing its ability to absorb and hold water, which can lead to more surface runoff and worsen flooding.

• Reduced Biodiversity & Soil Health: Tilling disrupts vital soil organisms (worms, microbes) and destroys channels, decreasing biodiversity, harming soil structure, and increasing compaction, leading to reliance on fertilizers. 

Causes of Compaction

• Compression of soil by machines

• Grazing livestock

• Humans

• Reduces ability to hold moisture

Effects of Compaction

• Dry soil erodes more easily

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

Nutrient Deletion

• Repeatedly growing crops on the same soil, removing key nutrients over time

• Reduces ability to grow future crops

Soil Material

Sand > Silt > Clay

Soil Texture

• The % of sand, silt, and clay in a soil

• Always adds up to 100

Porosity

• The amount of pore space of a soil

• More sand in a soil = higher porosity

  • Easier for water and air to enter

  • Air and water can enter sandy soil more easily

• More clay in a soil = less porosity

  • Harder for water and air to enter

Permeability

How easily fluids can flow through a material such as soil or rock

• High permeability: Soil/rock lets water & fluids pass quickly

• Low permeability: Slow water flow (like clay), good for filtering/holding water but can cause waterlogging and runoff

• More porosity, more permeability

Water Holding Capacity

• A soil's ability to retain moisture against gravity for plant use

• High permeability = low capacity

• Low permeability = high capacity

Chemical Properties of Soil

• Nutrient and mineral levels that plants and animals need to apply

• Fertilizers can help increase nutrients (N, P, K) for plant growth (might not be good for soil organisms)

• Tests for N, P, K acidity

  • Nitrate is usable with plants

Biological Properties of Soil

• Plants, animals, and bacteria

• Plants are ecosystems that regulate nutrient cycling and soil density (number of pores)

Soil Nutrients in Soil Fertility

Increases Soil Fertility

• Organic matter (releases nutrients)

• Humus (holds and releases nutrients)

• Clay (negative and positive charged nutrients bind)

• Bases

Decreases Soil Fertility

• Acids leaching positive nutrients

• Excessive rain/irrigation leaches nutrients

• Excessive farming depletes nutrients

• Topsoil erosion

Water Capacity in Soil Fertility

Increases Soil Fertility

• Aerated soil (biological activity)

• Compost/humus/organic matter

• Clay content

• Root structures, especially natives

Decreases Soil Fertility

• Compacted soil

• Topsoil erosion

• Sand

• Root losses

Texture Test

• Let settle in a jar of water

• Tells the % of sand, silt, and clay

• Tells how porous/permeable the soil is

Permeability Test

• Test by timing water when it’s draining through a column

• Tells how easily water drains through soil

  • Too high permeability: Soil dries out

  • Too low permeability: Roots don’t get water/drown

pH Test

• Test by pH strip

• Tells how acidic (low pH) or basic alkaline (high pH) the soil is

• More acidic = less nutrient availability

Color Test

• Test by comparing with Munsell Soil Color Book

• The darker, the more humus there is

• More humus = more nutrients and moisture

Nutrient Level Test

• Test by measuring

• Higher nutrient levels = more plant growth

• Lower nutrient levels = More acidic soil

Nitrogen

• ~78%

• Mostly in gas form (unusable to plants)

Oxygen

• ~21%

• Produced by photosynthesis in plants

• Needed for human/animal respiration

Argon

• ~0.93%

• Inert, noble gas

Water Vapor

• 0-4%

• Varies by region and conditions

• Acts as a temporary greenhouse gas, but is less concerning than CO₂

• Quickly cycles through the atmosphere

Carbon Dioxide

• ~0.04%

• Most important greenhouse gas

• Leads to global warming

• Removed from the atmosphere by photosynthesis

Atmospheric Layers

• Exosphere

• Thermosphere

• Mesosphere

• Stratosphere

• Troposphere

Exosphere

Outermost layer atmosphere that merges with space

Troposphere

• Absorbs harmful x-rays and UV radiation

• Charged gas molecules glow under intense radiation, producing northern lights

• Increasing temperature gradient because of its high solar energy absorption

• Hottest place on earth (3,100F)

Stratosphere

• Less dense due to less pressure from the layers above

• Thickest ozone layer

• Absorbs UV-B and UV-C rays, which can mutate DNA and cause lung damage

• Increasing temperature gradient because its top layer is warmed by UV rays

Mesosphere

• Density decreases, leaving fewer molecules to absorb the sun

• Coldest place on Earth (-150F)

• Decreasing temperature gradient

Troposphere

• Most dense due to the pressure of other layers above

• Where climate occurs

• Most of atmosphere’s gas molecules are here

• Ozone in the troposphere is harmful to humans and damages plant stomata

• Forms smog

Hadley Cell

• A convection cell where warm air rises and cold air descends

• Warm air holds more moisture and has lower pressure

• Colder air expands and cools to sink, unable to hold as much vapor

• Wind blows up from the equator

• Wind blows down from 30

Coriolis Effect

• Deflection of moving objects (like air and water) on Earth due to the planet's rotation

• 0-30 wind moves E → W because the Earth spins W → E

• 30-60 wind moves W → E because the earth spins faster at 30 than 60

Eastern Trade

• 0-30 winds blow E → W

• Drives ocean currents clockwise in N hemisphere, counterclockwise in S hemisphere

Westerlies

• 30-60 winds blow W → E

• Drives patterns of N in America

Watershed

• All the land that drains into a specific body of water

• Boundaries are determined by the slopes and ridges that divide this

• More vegetation = more infiltration and groundwater recharge

• Greater slope = faster velocity of runoff and more soil erosion

• Soil permeability determines the runoff vs infiltration rates

• Human activities

  • Impacts H₂O quality from agriculture, clearcutting, urbanization, dams, mining

Estuary

Fresh + salt water nutrients in sediment, brackish water (productive)

Eutrophication

Algae bloom due to N/P increase → Less sunlight → Plants below the surface die → Bacteria use up O₂ for decomposition → Hypoxia (lack of oxygen) and dead zones

Major Nitrogen/Phosphorous Sources

• Discharge from sewage treatment plants

• Animal waste from CAFOS/factory farms

  • CAFOS is a concentrated animal feeding operations

• Synthetic fertilizer from agricultural fields and lawns

Major Pollutants

• Endocrine disruptor (from sewage treatment)

• Sediment pollution

  • Increases turbidity (reduced photosynthesis) and covers over rocky streambed habitats

What is climate largely determined by?

• Insolation

  • The latitude affects the angle of insolation and atmosphere

• Equator

  • Receives the most intense insolation

  • Higher temperature

  • Air rises

  • High precipitation

• Higher latitudes

  • Receives less insolation

  • Cooler

  • Less precipitation (especially at 30 degrees)

Windward

Warm moist air from the ocean hits this side of the mountain, rises, cools (condensing H₂O vapor and causing rain), and allows for lush green vegetation

Leeward

• Dry air descends down this side of the mountain, warming as it sinks

  • Leads to arid desert conditions

Gyre

Large ocean circular patterns due to global wind

• Clockwise in H hemisphere and counterclockwise in the S hemisphere

Upwelling Zones

Areas of ocean where winds blow warm surface water away from a land mass, drawing up colder, deeper water to replace it

• Brings O₂ and nutrients to surface → productive fishing

Thermohaline Circulation

Connects all the world’s oceans, mixing salt, nutrients, and temperature throughout

• Warm water from the Gulf of Mexico moves towards the North Pole

• Cools and evaporates as it moves toward poles

• Saltier and cooler water at poles is more dense, making it sink

• Spreads along ocean floor

• Rises back up into shallow warm ocean current at upwelling zone

El Niño Southern Oscillation (ENSO)

Pattern of shifting atmospheric pressure and ocean currents in the pacific ocean between South America and Australia/Southeast Asia

• Oscillates/shifts regularly from El Niño to La Niña (cooler, drier) conditions along the coast of South America

Normal Year Compared to El Niño and La Niña

• Trade winds blow equator water W ← E

• South America: High pressure in the East Pacific

  • Cool H₂O upwelled off coast of SA

  • Cool temperature and good fisheries

• Australia/Southeast Asia: Low Pressure

  • Warm equator current brings heat and precipitation to AUS/SE

El Niño

• Trade winds weaken, then reverse to W → E

• South America: Low pressure in East Pacific

  • Suppressed upwelling of South American coast, damaging fisheries

• Australia/Southeast Asia: High pressure in the West Pacific

  • Cooler, drier conditions

La Niña

• Trade winds blow stronger than the normal trade winds, going W ← ← E

• South America: Low pressure

  • Stronger upwelling and better fishes in South America than normal

• Australia/Southeast Asia: High pressure

  • Rainier, warmer, increased monsoons