Earth's Structure and Plate Tectonics

• Geography examines Earth's landscapes, environments, and human-environment connections.
• Physical geography concerns itself with Earth's natural processes.
• The focus is on patterns pertaining to climate, landforms, vegetation, soils, and water.
• Physical geography studies how these patterns are formed and how they change.
• Understanding the natural world is aided by physical geography.
• Environmental studies and resource management are built upon its foundations.

Earth's Structure and Plate Tectonics

• Earth has layers: crust, mantle, and core.
• The crust, solid and outermost.
• The mantle, mostly solid, lies beneath the crust.
• The core, Earth's center, is mostly iron and nickel, and has a solid inner part and liquid outer part.
• Plate tectonics explains the movement of Earth's lithosphere.
• The lithosphere is split into plates.
• They float on the semi-molten asthenosphere.
• Mantle convection currents drive the plates.
• Plate boundaries: convergent, divergent, and transform.
• Convergent boundaries: plates collide, forming mountains, volcanoes, and subduction zones.
• Divergent boundaries: plates separate, causing seafloor spreading and rift valleys.
• Transform boundaries: plates slide past each other, causing earthquakes.
• Plate tectonics shapes the surface and causes geological events.

Climate and Weather

• Climate: long-term weather patterns of a region.
• Weather: short-term atmospheric conditions at a specific time and place.
• Key elements: temperature, precipitation, wind, and humidity.
• Climate is affected by latitude, altitude, nearness to water, and ocean currents.
• Seasonal changes in solar radiation are due to Earth's tilt.
• Atmospheric circulation distributes heat.
• The Coriolis effect deflects winds due to Earth's spin.
• Ocean currents move heat from the equator toward the poles.
• The greenhouse effect traps heat.
• Greenhouse gases: carbon dioxide, methane, and water vapor.
• Climate change: long-term shifts in temperature and weather.
• These shifts are caused by greenhouse gas increases due to human activity.

Landforms and Processes

• Landforms: natural surface features.
• Examples: mountains, plains, plateaus, and valleys.
• Processes shaping landforms: weathering, erosion, and deposition.
• Weathering breaks down rocks.
• Physical weathering: mechanical disintegration.
• Chemical weathering: alteration of rock composition.
• Erosion: removal and transport of weathered material.
• Primary agents of erosion: water, wind, and ice.
• Deposition: laying down eroded material elsewhere.
• Rivers create valleys, floodplains, and deltas.
• Glaciers carve U-shaped valleys and drop moraines.
• Wind forms dunes and loess deposits in dry areas.
• Coastal landforms are shaped by waves and tides.
• Examples: cliffs, beaches, and barrier islands.

Hydrology and Water Resources

• Hydrology: the study of water's movement, distribution, and quality.
• The hydrologic cycle: continuous water circulation.
• This includes evaporation, transpiration, condensation, precipitation, and runoff.
• Surface water: rivers, lakes, and wetlands.
• Groundwater: underground water in aquifers.
• Watersheds: land areas draining into a common outlet.
• Water is critical for people and ecosystems.
• Water scarcity affects many areas.
• Overuse, pollution, and climate change cause scarcity.
• Water management: strategies for sustainable use.
• Examples: irrigation, dams, and water treatment.

Biogeography and Ecosystems

• Biogeography studies the distribution of species and ecosystems.
• It examines climate, topography, soils, and historical events.
• Ecosystems: communities of living things interacting with their environment.
• Biomes: large ecosystems with specific climate and vegetation.
• Examples: forests, grasslands, deserts, and tundra.
• Biodiversity: the variety of life forms.
• It is key for ecosystem stability and resilience.
• Habitat loss, deforestation, and pollution threaten biodiversity.
• Conservation protects species and ecosystems.
• Examples: national parks, reserves, and habitat restoration.

Soils

• Soil is dynamic, natural, with minerals, organic matter, water, air, and organisms.
• It forms from rock weathering and organic decomposition.
• Soil horizons: distinct layers in a soil profile.
• The O horizon: surface layer, with lots of organic matter.
• The A horizon: topsoil, biologically active.
• The B horizon: subsoil, minerals accumulate there.
• The C horizon: weathered parent material.
• Soil properties: texture, structure, pH, and nutrient content.
• Soil texture: proportion of sand, silt, and clay.
• Soil structure: arrangement of soil particles.
• Soil pH: acidity or alkalinity measurement.
• Soil fertility: ability to support plant growth.
• Soil erosion degrades soil and reduces agricultural productivity.
• Soil conservation: conservation tillage, terracing, and crop rotation.

Natural Hazards

• Natural hazards threaten life and property.
• Examples: earthquakes, volcanoes, floods, droughts, and landslides.
• Earthquakes: sudden energy release in Earth's crust.
• Volcanoes: magma reaching the surface.
• Floods: excessive rain or snowmelt.
• Droughts: long periods of low precipitation.
• Landslides: soil and rock moving downslope.
• Hazard assessment identifies and maps hazards.
• Risk management reduces vulnerability to hazards.
• Examples: early warning systems, evacuation plans, and building codes.