Driven by uneven solar heating (equator vs. poles) and the Coriolis effect (Earth's rotation curving wind direction). Circulation cells (Hadley, Ferrel, polar) set where deserts and rainforests form.
Solar Radiation & Seasons
Earth's 23.5° axial tilt, not distance from the Sun, causes the seasons. The equator receives the most concentrated, year-round solar energy.
Geography & Climate
Latitude, elevation, ocean currents, and the rain-shadow effect (dry leeward side of mountains) shape a region's climate.
El Niño & La Niña (ENSO)
El Niño weakens trade winds and warms the eastern Pacific, cutting upwelling and fisheries off South America; La Niña is the opposite, cooler phase.
Watersheds
Land area draining into one water body. Land use anywhere in a watershed affects water quality downstream.
Soil Formation
Five factors: climate, parent rock, topography, organisms, time. Produces distinct horizons: O, A (topsoil), B, C, R.
Wind/water strip topsoil; worsened by deforestation, overgrazing, tillage. Prevented by contour plowing, terracing, no-till, cover crops.
The key terms you must know
Plate tectonics — the movement of Earth's lithospheric plates over the mantle.
Subduction — one tectonic plate sinking beneath another at a convergent boundary.
Coriolis effect — the deflection of moving air/water caused by Earth's rotation.
Watershed — the land area draining into a specific body of water.
Soil horizon — a distinct layer within soil (O, A, B, C, R).
Topsoil (A horizon) — the nutrient-rich layer most critical for plant growth.
Soil texture — the proportion of sand, silt, and clay in soil.
Permeability — the rate water moves through soil.
Soil erosion — the loss of topsoil to wind or water.
Ozone layer — the stratospheric layer that absorbs harmful UV radiation.
Rain shadow — the dry region on the leeward (downwind) side of a mountain range.
El Niño (ENSO) — a periodic warming of the eastern Pacific that weakens trade winds and disrupts weather and fisheries worldwide.
Key themes to remember
Plate boundaries explain almost all major geologic hazards. Most volcanoes and earthquakes cluster along plate edges.
Solar energy drives atmospheric circulation. Uneven heating between the equator and poles is the root cause of global wind patterns.
Watersheds connect land use to water quality. What happens anywhere upstream affects everyone downstream.
Soil takes centuries to form but can erode in years. This asymmetry is why soil conservation matters so much for agriculture.
Earth's systems are interconnected. Geology (soil parent material), atmosphere (climate), and hydrology (watersheds) all shape soil and ecosystem function together.
Common exam traps
Don't confuse the three plate boundary types. Convergent = collide/subduct, divergent = separate, transform = slide past (no new/destroyed crust).
The ozone layer is in the stratosphere, not the troposphere. Weather happens in the troposphere; UV protection happens in the stratosphere.
The A horizon is topsoil — don't confuse it with the O horizon (organic litter on top) or the B horizon (subsoil below).
Permeability and porosity are related but different. Porosity = how much space for water; permeability = how fast water actually moves through.
Volcanic cooling is temporary, not permanent. Don't describe it as a long-term climate fix — aerosols settle out within a few years.
Watershed boundaries don't follow political borders. They follow topography (drainage divides), which can cross state or country lines.