AP Environmental Science: Earth Systems and Resources

A comprehensive vocabulary study set covering Earth's internal structure, plate tectonics, soil formation and properties, atmospheric layers, global air and water circulation patterns, ENSO phases, and watershed ecology.

Core

Dense mass of nickel, iron, and radioactive elements at the center of Earth that releases large amounts of heat.

Asthenosphere

Semi-molten, flexible outer layer of the mantle located directly beneath the lithosphere.

Lithosphere

Thin, brittle layer of rock that includes the solid upper mantle and crust, broken up into tectonic plates.

Divergent Plate Boundary

A plate boundary where tectonic plates move away from each other as rising magma plumes from the mantle force them apart, forming mid-oceanic ridges, volcanoes, seafloor spreading, rift valleys, and earthquakes.

Transform Fault Plate Boundary

A plate boundary where tectonic plates slide past each other in opposite directions, creating faults that produce earthquakes when locked rock edges suddenly slip.

Convergent Plate Boundary

A plate boundary where tectonic plates collide or move towards each other, resulting in subduction or crustal uplift that forms mountains, island arcs, earthquakes, and volcanoes.

Subduction Zone

A convergent boundary zone where a denser tectonic plate is forced beneath an adjacent plate and melts back into magma within the mantle.

Ring of Fire

A horseshoe-shaped pattern of volcanoes and earthquakes situated along the boundaries of the Pacific Plate, characterized by offshore island arcs such as Japan.

Hotspots

Areas in the mantle where exceptionally hot plumes of magma rise to the lithosphere, forming mid-ocean volcanic island chains such as Iceland and Hawaii.

Humus

The dark, primary organic component of soil formed from the decomposition of biomass, including dead leaves, animal remains, and waste.

Weathering

The mechanical, chemical, or biological breakdown of parent rock into smaller mineral fragments, initiating the process of soil formation.

Erosion

The physical transport of weathered rock fragments and soil particles across distances by wind or rain, ending with deposition in a new location.

O-Horizon

The surface organic horizon composed of fresh and decomposing plant litter, roots, and animal waste that supplies nutrients and reduces surface evaporation of $H_2O$.

A-Horizon

The topsoil layer composed of mixed humus and weathered minerals from parent material, displaying the highest biological activity from earthworms and microbes.

B-Horizon

The subsoil layer beneath topsoil, primarily consisting of mineral deposits and accumulated leached nutrients with little to no organic matter.

C-Horizon

The least weathered soil layer directly above the bedrock, consisting of broken rock fragments and devoid of organic material.

Soil Degradation

The decline in soil quality and its capacity to support plant growth, commonly caused by topsoil erosion, machinery or livestock compaction, and agricultural nutrient depletion.

Soil Texture

The relative proportion of sand, silt, and clay mineral particles present within a soil sample, always summing to $100\%$.

Soil Texture Chart

A ternary diagram used to determine soil texture classifications and evaluate water-holding capacity based on the percentages of sand, silt, and clay.

Porosity

The measurement of open pore space between particles within a soil sample, which increases with higher proportions of large sand particles.

Permeability

The speed and ease with which water drains through open pore spaces in a soil column.

$H_2O$ Holding Capacity

The capacity of a soil to retain moisture against drainage, which maintains an inverse relationship with both porosity and permeability.

Loam

An optimal soil texture classification for agricultural plant growth that balances drainage and water retention, typically comprising $40\%$ sand, $40\%$ silt, and $20\%$ clay.

Troposphere

The lowest and densest atmospheric layer ($0-16\,\text{km}$), where almost all weather occurs, containing the majority of atmospheric gas molecules and harmful ground-level ozone ($O_3$).

Stratosphere

The second atmospheric layer ($16-60\,\text{km}$), which holds the protective ozone layer that absorbs incoming UV-B and UV-C solar radiation.

Mesosphere

The middle atmospheric layer ($60-80\,\text{km}$), where meteors burn up from friction, representing the coldest atmospheric region at $-150^\circ\text{F}$.

Thermosphere

The hottest atmospheric layer ($3{,}100^\circ\text{F}$), where energetic solar X-rays and UV rays are absorbed, causing charged gas molecules to produce the aurora borealis.

Albedo

The fraction of incoming solar radiation reflected by a surface, where darker surfaces possess low albedo and emit more absorbed energy as infrared heat.

Urban Heat Island

A localized microclimate effect where developed cities experience elevated temperatures compared to rural surroundings due to the low albedo of dark blacktop surfaces.

Coriolis Effect

The apparent rotational deflection of air masses and moving objects across Earth, turning winds moving from $0-30^\circ$ to the west and winds moving from $30-60^\circ$ to the east.

Trade Winds

Equatorial surface winds between $0-30^\circ$ latitude that consistently blow from east to west, driving equatorial ocean surface currents.

Westerlies

Prevailing mid-latitude surface winds between $30-60^\circ$ latitude that blow from west to east, guiding major North American weather tracks.

Gyres

Large-scale circular ocean surface current systems driven by global winds, rotating clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

Upwelling Zones

Coastal marine regions where winds push warm surface waters offshore, allowing cold, nutrient- and oxygen-rich deep water to rise and sustain highly productive fisheries.

Thermohaline Circulation

A continuous global oceanic conveyor system driven by density gradients from salinity and temperature differences, distributing heat and dissolved minerals globally.

El Niño Southern Oscillation (ENSO)

A cyclical shift in atmospheric pressure and equatorial sea surface temperatures across the tropical Pacific Ocean between the Americas and Australasia.

Normal Year (Pacific Conditions)

Standard equatorial Pacific circulation where easterly trade winds push warm water west toward Australia, supporting strong, cold coastal upwelling off western South America.

El Niño

An ENSO phase where equatorial trade winds weaken or reverse ($\text{W} \rightarrow \text{E}$), suppressing South American upwelling and causing warm, rainy conditions in the Americas alongside droughts in Southeast Asia and Australia.

La Niña

An ENSO phase marked by stronger-than-normal easterly trade winds, enhanced cold-water upwelling off the coast of South America, and increased precipitation and monsoon intensity across Southeast Asia.

Watershed

A distinct drainage basin where all precipitation and surface runoff funnel down topographical slopes into a shared body of water such as a river, lake, or bay.

Eutrophication

A degradation cascade occurring when excess nitrogen ($N$) and phosphorus ($P$) induce algal blooms, blocking light and driving microbial decomposition that depletes dissolved oxygen (hypoxia).

Turbidity

A measure of water cloudiness resulting from suspended soil and sediment particles, which impedes aquatic photosynthesis and clogs the gills of aquatic organisms.

Riparian

The terrestrial ecosystem and vegetated zone immediately flanking and interacting with a freshwater stream or riverbank.