AP Environmental Science Unit 4 — Earth Systems and Resources.
This unit covers plate tectonics, soil composition and atmosphere layers — essential concepts for AP Environmental Science. Use our interactive study games to test your understanding, or review questions in traditional format below.
Pick a mode. Play.
Answer questions as fast as you can. 2 minutes on the clock. Build streaks for bonus points!
Don't want to play?
Review the questions traditionally. Click to expand.
Questions loading...
Focus on understanding.
Focus on understanding core concepts before memorizing details. Use the game modes to test yourself repeatedly — spaced repetition is proven to boost long-term retention.
Ready for college?
See which colleges accept your AP Environmental Science score.
This unit covers plate tectonics, soil composition and atmosphere layers — essential concepts for AP Environmental Science. Use our interactive study games to test your understanding, or review questions in traditional format below.
Key Concepts Breakdown
1 Plate Tectonics
Students must understand the types of plate boundaries (convergent, divergent, transform) and the geological events associated with each. The movement of tectonic plates drives processes like volcanic activity, earthquakes, mountain building, and seafloor spreading. The rock cycle and soil formation are also connected to tectonic processes.
Key Points
- Convergent boundaries: oceanic-continental subduction creates volcanoes and trenches; continental-continental collision creates mountain ranges (e.g., Himalayas)
- Divergent boundaries: plates move apart, magma rises to form new crust; mid-ocean ridges and rift valleys form here
- Transform boundaries: plates slide horizontally past each other, producing earthquakes but no volcanism (e.g., San Andreas Fault)
- Subduction zones recycle oceanic crust back into the mantle; oceanic crust is denser than continental crust
A student is told that two oceanic plates are converging. One plate subducts beneath the other. What surface features would most likely form at this boundary?
When two oceanic plates converge, the denser plate subducts, creating a deep-ocean trench at the subduction zone. As the subducting plate melts in the mantle, magma rises and erupts, forming a chain of volcanic islands called an island arc (e.g., the Aleutian Islands). Earthquakes are also common due to friction along the subducting slab.
2 Soil Composition
Students must know the four components of soil (minerals, organic matter/humus, water, air), the five soil-forming factors (CLORPT: climate, organisms, relief/topography, parent material, time), and the structure of a soil profile with its horizons. Soil texture (relative proportions of sand, silt, and clay) determines water retention and fertility, which are heavily tested.
Key Points
- Soil horizons: O (organic litter), A (topsoil, humus-rich), E (eluviation/leaching), B (subsoil, mineral accumulation), C (weathered parent material), R (bedrock)
- Loam (balanced sand/silt/clay mixture) has the best agricultural properties: good drainage and high nutrient retention
- Clay soils retain water and nutrients well but drain poorly; sandy soils drain quickly but have low fertility
- Soil erosion removes the nutrient-rich A horizon first; this is why topsoil loss is a critical agricultural problem
A farmer notices that after heavy rainfall, water pools on the surface of her fields and crops show signs of root rot. A soil analysis shows 60% clay, 30% silt, and 10% sand. What is the most likely cause, and what amendment could help?
The soil is classified as clay-dominant, which means particles are very fine and tightly packed, leaving little pore space for water to drain through — causing waterlogging. Root rot occurs when roots are deprived of oxygen in saturated soil. Adding coarse organic matter (compost) or sand can improve drainage by increasing pore space, while also boosting microbial activity and nutrient availability.
3 Atmosphere Layers
Students must know the four main layers of the atmosphere (troposphere, stratosphere, mesosphere, thermosphere), their altitude ranges, temperature trends, and key processes occurring in each. The exam focuses especially on the troposphere (weather, greenhouse effect) and stratosphere (ozone layer, UV absorption). Understanding temperature inversions and their environmental consequences is also tested.
Key Points
- Troposphere (0–12 km): temperature decreases with altitude; contains 75% of atmospheric mass and all weather; greenhouse gases trap heat here
- Stratosphere (12–50 km): temperature increases with altitude due to ozone absorbing UV radiation; ozone layer (O3) peaks around 20–30 km
- Mesosphere (50–80 km): temperature decreases with altitude; meteors burn up here
- A temperature inversion in the troposphere traps pollutants near the surface because the normal lapse rate is reversed — warm air sits above cooler air, preventing convective mixing
On a calm winter morning in a city surrounded by mountains, air quality monitors record dangerously high levels of particulate matter and ground-level ozone near street level, despite low industrial activity. What atmospheric condition best explains this?
This scenario describes a temperature inversion: a layer of warm air has settled above the cooler air near the surface, acting as a lid that prevents the normal upward mixing of air. Pollutants from vehicles and other sources become trapped in the cool surface layer and accumulate to harmful concentrations. The mountain topography worsens the effect by limiting horizontal airflow and preventing dispersion.
Questions, answered.
What is Earth Systems and Resources?
Earth Systems and Resources is Unit 4 of AP Environmental Science, covering plate tectonics, soil composition and atmosphere layers.
How to study for AP Environmental Science Unit 4?
Start with the Quick Summary above, review the Key Concepts, then test yourself with our interactive study games. Aim for 80%+ accuracy before moving on.
How many questions are in this unit?
This unit has 30+ review questions across 5 different game modes.