10-15% of The AP Test

Topics

4.1 Plate Tectonics

4.2 Soil Formation and Erosion

4.3 Soil Composition and Properties

4.4 Earth’s Atmosphere

4.5 Global Wind Patterns

4.6 Watersheds

4.7 Solar Radiation and Earth’s Seasons

4.8 Earth’s Geography and Climate

4.9 El Niño and La Niña

These notes are based on Mr Jordan Dischinger-Smedes’s YouTube videos and the fill in template notes for these videos created by Carolyn Kelleher Mendonca. Some changes were made. Videos available here.

Good luck on the AP Test! 🩷

4.1 - Tectonic Plates

Layers of the Earth

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

• Mantle: soft liquid of magma surrounding core, kept soft by intense heat from core. Because of convection currents, it is almost constantly moving.

• 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

Types of Plate Boundaries

Divergent Plate Boundary

• Plates move away from each other

• Rising magma plume from mantle forces plates apart

  • Forms: Mid-oceanic ridges, volcanoes, seafloor spreading, and rift valleys on land.

Convergent Fault Plate Boundary

• Plates move towards each other

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

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

Transform Plate Boundary

• Plates slides past each other in opposite directions

• Form earthquakes

Convection Cycles

• Occur in Divergent Plate Boundaries

• Magma heated by earth’s core rises towards the lithosphere, melting the 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 plates into cont. (subduction zone)

  • Sinking oceanic plate melts back into magma

  • Also forces magma up, creating narrow, coastal mountains (andes) on land

Subduction in Convergent Boundaries

Oceanic-Oceanic - One plate subducts underneath the other

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

  • Island arcs

• Off-shore trench

Oceanic-Continental: Dense oceanic plate subducts beneath continental Plate & melts back into magma

• Forces magma up to lithosphere surface

• Coastal Mountains (andes), volcanoes on land, trenches, tsunamis

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

• Ex: Himalayas

Effects of Transform Boundaries

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

  • Earthquakes are the most common activity

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

  • Pressure builds as keep sliding
    but edges stay stuck

  • When stress overcomes, plates suddenly release, slide past each other and release energy

Ring of Fire: pattern of volcanoes all around pacific plate

• Offshore island arcs (Japan)

Transform Faults: likely location of earthquakes.

Hotspots: areas of especially hot magma rising up to lithosphere

• Mid-ocean islands like Hawaii and Iceland

Continental Drift Theory:

4.2 - Soil

Soil is a mix of geological (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

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

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

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

Habitat: provides a habitat for organisms like earthworms, fungi, bacteria, moles, and slugs.

Weathering and Erosion

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 leads to 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 ground

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

    • Sand, silt, and clay

    • Minerals

• From above ground

  • Breakdown of organic matter adds humus (organic materials) to soil

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

Effects on Soil Formation

• Parent material: soil pH, nutrient content

• Topography: steep slope = too much erosion; more level ground = deposition

• Climate: warmer = warmer breakdown of org. matter; colder. = more weathering, erosion + deposition

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

Soil Horizons (know OABC, not E or R) Mnemonic: Obviously Alligators Boycott Cats.

O-Horizon: layer of organic (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 agriculture) and a loss of vegetation disturb soil and make it more easily eroded by wind and rain

• Loss of topsoil dries out soil, removes nutrients and organisms that recycle nutrients

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

• Dry soil erodes more easily

• Dry soil supports less plant growth, less root, 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

4.3 - Soil Composition and Properties

Soil Particle Size, Texture, and Porosity

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

Sand > Silt > Clay

(biggest to smallest)

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

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

• Because sand is bigger, it has bigger pores (empty spaces between particles)

  • This allows air and water to enter sandy soil easily-

  • Clay has the 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)

Soil Texture Chart

• Soil texture is determined by clay, sand, silt %

  • Ex: Loam = 40-40-20, sand, silt, clay

  • Or 45% sand 35% silt, 20% clay: loam

• Tips for using Soil Texture Chart

  • Always start on bottom with sand %

  • Move out diagonally to the point where sand + silt meet

  • Then go straight over to clay

  • Make sure it adds up to 100%

Porosity, permeability, and H2O Holding Capacity

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

• Permeability: how easily water can move through a soil

  • More porous = 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

• 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: The ability of soil to support plant growth

Nutrients

• N, P, K, Mg, Ca, Na

• Factors that increase soil nutrients

  • Organic matter (releases nutrients)

  • Humus (holds and releases nutrients)

  • Decomposer activity (recycles nutrients)

  • Clay (negative charge binds positive nutrients)

  • Bases (Calcium carbonate and limestone)

    • Adding Calcium Carbonate/Limestone can allow soil to better hold onto nutrients!

• Factors that decrease soil nutrients

  • Acids leach pos. charge nutrients

  • Excessive rain/irrigation leaches nutrients

  • Excessive farming depletes nutrients

  • 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 structures, especially natives

• Factors that decrease H2O holding cap.

  • Compacted soil (machines, cows)

  • Topsoil erosion

  • Sand

  • Root loss

4.4 - Atmosphere

• Nitrogen (N2) - 78%

  • Mostly in the form of N2 (unuseable to plants without being fixed)

• Oxygen (O2) - 21%

  • Produced by photosynthesis in plants & needed for human/animal respiration

• Argon (Ar) - 0.93%

  • Inert, noble gas

• Water Vapor (H2O) - 0.4%

  • Varies by region & conditions; acts as a temporary GHG, but less concerning than CO2

  • Quickly cycles through atmosphere

• Carbon Dioxide (CO2) - 0.04%

  • Most important GHG; leads to global warming

  • Removed from atm. by photosynthesis

Mnemonic for layers - The Silly Monkeys Twirl Endlessly

Troposphere:

• Tropo means change (weather occurs here) - 0-16 km, most dense due to pressure of other layers above it

• Most of atmosphere’s gas molecules are found here

• Ozone (O3) in the troposphere is harmful to humans (respiratory irritants) & damages plant stomata, and forms smog

• Most dense layer

Stratosphere: (“S” for second)

• 16-60 km; less dense due to less pressure from layers above

• Thickest O3 (ozone) layer is found here; absorbs UV-B & UV-C rays which can mutate DNA of animals (cancer)

Mesosphere:

• Meso is for middle; 60-80 km, even less dense

Thermosphere:

• Therm = hottest temp;

• absorbs harmful X-rays & UV radiation

• Charged gas molecules glow under intense solar radiation producing northern lights (aurora borealis)

Exosphere:

• Outermost layer where the atmosphere merges with space

Troposphere: Temperature decreases as air gets further from warmth of earth’s surface

Stratosphere: Temperature increases because top layer of stratosphere is warmed by UV rays (like pool surface)

Mesosphere: Temperature decreases because density decreases, leaving fewer molecules to absorb sun

• Coldest place on earth (-150F)

Thermosphere: Temperature Increases due to absorption of highly energetic solar radiation

• Hottest place on earth (3,100F)

4.5 - Wind Patterns

Air Properties

• Warm air rises

• Warm air holds more moisture

• Rising air expands and cools

• Cool air can’t hold as much H2O vapor (condenses → rains)

• After cooling & expanding, air sinks

Coriolis Effect

• Coriolis Effect is the deflection of objects traveling through the atmosphere is due to the spin of the earth

• Air at 30° moves back due to the low pressure of equator

• Wind between 0-30° moves. from E→W

  • Due to earth spinning W→E

• Wind between 30-60° moves W→E

  • Due to earth spinning faster at 30° then 60°

Global Wind Patterns

• Air moves out from 30° to 0° and 60° due to H pressure at 30° & and L pressure at 0° and 60°.

  • Air rising at equator = low pressure,

  • Air sinking down at 300 = high pressure

• 0-30° winds blow E → W (Eastern Trade Winds)

  • Drives ocean current clockwise in N and counterclockwise in S

• 30- 60°: winds blow W → E (Westerlies Wind)

  • Drives weather patterns of N America

Hadley Cells rise at 0° and drop and 30°

Ferrell Cells drop at 30° and rise at 60°

Polar Cells rise at 60° and drop at 90° (the poles).

4.6 - Watersheds

A watershed is an anywhere where water collects. It can be filled by runoff or rivers. It’s often a part of a river system and water will continue to flow down until it reaches the ocean.

• The more vegetation, the less runoff, so the less watershed volume

• The greater slope, the more watershed volume

• Soil Permeability determines how much runoff there is

Polluted runoff and rivers can pollute a watershed

Solutions to Watershed Pollution

• Cover crops (pulls pollutants from the soil, not used for profit)

• Riparian buffer (plants along the water's edge)

4.7 - Radiation and Seasons

Insolation is the amount of solar radiation (energy) that reaches an area. It is measured in Watts per Meters squared.

• Solar intensity of insolation (W/m2) depends on:

  1. Angle: how directly rays strike earth’s surface

  2. The amount of Atmosphere sun’s rays pass through

• The Equator has higher insolation than higher latitudes

• The orbit of the earth around sun & the earths tilt on its axis changes angle of sun’s rays

• This causes varying insolation, varying length, and seasons.

• The tilt of earth’s axis stays fixed during orbit

  • June & December Solstices: N or S hemisphere is maximally tilted toward sun (summer/winter)

  • March & Sept. Equinox: N & S hemispheres equally facing sun (Equinox - Equal)

• Albedo: the proportion (percentage) of light that is reflected by a surface

• Surfaces with higher albedo reflect more light, and absorb less (ice/snow)

  • Absorb less heat

• Surfaces with low albedo reflect less light, and absorbs more (water)

  • Absorb more heat

• surface temperature is affected by albedo

• When sunlight is absorbed by a surface, it gives off infrared radiation (heat)

  • Areas with lower albedo, absorb more sunlight light (heat)

• Urban Heat Island: urban areas are hotter than surrounding rural area due to low albedo of blacktop

• Polar regions are colder in part due to higher albedo

4.8 - Climate and Geography

• Climate is largely determined by insolation (latitude, angle of insolation, & atmosphere)

  • Higher latitudes: cooler, less precipitation (especially at 30 degrees latitude)

  • The equator receives the most intense insolation: higher temp, air rises, high precipitation

• Geography also plays a role

  • Mountains: disrupt wind & produce rain shadow effect

  • Oceans: moderate temperature & add moisture to the air

  • Warm, moist air from ocean hits the “windward” side of the mountain, rises, cools, (condensing H2O vapor & causing rain) creating lush, green vegetation

  • Dry down “leeward” side of mtn, warming as it sinks

    • Leads to arid (dry) desert conditions.

• Eastern trade winds blow moist air from Atlantic across South Asia

  • Windward (E) side of Andes receives heavy rainfall

  • Leeward (W) side of Andes receives arid/dry air

  • ~30 latitude also contributes to lack of rain, high pressure, dry, descending air from Hadley cell

4.9 - El Niño and La Niña

• Gyres: large ocean circulation patterns due to global winds

  • (clockwise in N hemisphere, counterclockwise in S hemisphere)

  • Covers whole oceans

• Eastern Trade Winds between 0-30° push water along the equator E → W

• Westerlies between 30-60° push mid latitude currents W → E

Upwelling Zones: areas of ocean where winds blow warm surface water away from a land mass and draw up cold, deep water to replace it. Brings O2 and nutrients to the surface, so these areas have productive fisheries

Thermohaline Circulation

• Connects all of the world’s oceans, mixing salt, nutrients, and temperatures throughout

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

• Water cools and evaporates as it moves toward poles

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

• The water the spreads along ocean floor

• Rises back up into shallow warm ocean current upwelling zones

El Niño and La Niña

• ENSO: pattern of shifting atmospheric pressure & ocean currents in the pacific ocean between South America, Australia, and Southeast Asia.

• ENSO - El Nina Southern Oscillation

  • Oscillates, or shifts regularly from El nino (warmer, rainier) to La Nina (cooler, drier) conditions along coast of South America

La Niña conditions are just more extreme normal conditions.

• El Niño

  • No upwelling in Latin America

  • Warm Latin America water

  • Warm water in Asia

  • Droughts/no rainfall in Asia

  • Rainfall in Latin America

  • High Pressure in Asia

  • Low pressure in Latin America

• La Niña

  • Rain in Asia

  • Warm water in Asia

  • Cold water in Latin America

  • Upwelling in Latin America (good for fishing)

  • High pressure in Latin America

  • Low pressure in Asia