Unit 4 AP Environmental Science

Convergent

plates collide → mountain building, subduction zones, volcanoes, earthquakes

Divergent

plates move apart → seafloor spreading, rift valleys

Transform

plates slide past one another → earthquakes along faults

What is soil formation and what factors control its rate?

• Soil forms from weathering of parent rock + accumulation of organic matter.

• Influencing factors: climate (temperature, precipitation), organisms (plants, microbes), topography (slope), parent material, time.

O horizon:

organic matter (leaf litter, decomposing material)

A horizon (topsoil)

mineral particles + organic matter, plant roots

B horizon (subsoil):

accumulation of leached minerals (clays, iron, aluminum)

C horizon:

weathered parent rock material

R horizon:

unweathered bedrock

Sand (largest particle)

drains fastest, holds little water

Silt

moderate drainage and retention

Clay (smallest):

holds water strongly, poor drainage

Loam (balanced mix)

is best for plant growth.

What is the composition of Earth’s atmosphere (major gases & approximate percentages)?

• Nitrogen (N₂): ~78%

• Oxygen (O₂): ~21%

• Argon, CO₂, and trace gases: ~1% (including water vapor, ozone, etc.)

Troposphere

where weather occurs, temperature decreases with altitude

Stratosphere

contains ozone layer, temperature increases with altitude

Mesosphere

meteors burn up here, temperature decreases

Thermosphere

very thin air, auroras occur, temperature increases

Exosphere

transitional zone to space

What is the Coriolis effect, and how does it influence wind patterns?

• As Earth rotates, moving air is deflected: to the right in Northern Hemisphere, to the left in Southern Hemisphere.

• Causes curved wind paths, affecting trade winds, westerlies, and ocean currents.

Hadley cell

(0°–30° latitude): warm air rises near equator, moves poleward, sinks → creates trade winds

Ferrel cell

(30°–60°): intermediate cell, air moves opposite to Hadley and Polar cells

Polar cell

(60°–90°): cold air sinks at poles then moves equatorward near surface

What causes the seasons, and how does solar radiation vary with latitude?

• Earth’s axis is tilted ~23.5°, so during its orbit, each hemisphere is tilted toward or away from the sun at different times → seasons.

• At low latitudes (near equator), sunlight is more direct, so more intense radiation. At higher latitudes, sunlight is more oblique, less energy per unit area.

Define rain shadow effect and how it shapes regional climates.

• When moist air moves up a mountain, it cools and drops precipitation on windward side.

• On the leeward side, descending air is dry, creating a rain shadow—arid region behind the mountain.

What are El Niño and La Niña, and what are their global climate impacts?

• El Niño: trade winds weaken or reverse, warm surface water moves eastward; leads to altered precipitation patterns (e.g. wetter in some places, droughts in others)

• La Niña: exaggerated “normal” conditions, stronger trade winds; cooler-than-average waters along Pacific coast, opposite climate anomalies