FTCE Social Science 6-12 (037)

Physical geography examines Earth's natural systems, landforms, climate patterns, and physical processes that shape the planet's surface.

Earth consists of four major spheres: the lithosphere (solid earth), hydrosphere (water), atmosphere (air), and biosphere (living organisms). The lithosphere comprises three layers: the crust, mantle, and core. Continental crust is thicker but less dense than oceanic crust.

Plate tectonics theory explains how Earth's lithosphere is divided into large plates that float on the semi-fluid asthenosphere. Three types of plate boundaries exist: divergent boundaries where plates move apart creating rift valleys and mid-ocean ridges, convergent boundaries where plates collide forming mountains or subduction zones, and transform boundaries where plates slide past each other causing earthquakes.

Major landform types include mountains, plateaus, plains, and hills. Mountains form through folding, faulting, or volcanic activity. The Himalayas resulted from the collision of the Indian and Eurasian plates. The Appalachian Mountains are older, more eroded fold mountains. Volcanic mountains like Mount St. Helens form from magma eruptions.

Weathering breaks down rocks through mechanical processes (frost wedging, root growth, thermal expansion) and chemical processes (oxidation, carbonation, hydrolysis). Erosion transports weathered material via water, wind, ice, and gravity. Deposition occurs when transported sediments settle, creating features like deltas, alluvial fans, and sand dunes.

Glaciers shape landscapes through erosion and deposition. Alpine glaciers carve U-shaped valleys, cirques, arêtes, and horns. Continental glaciers create features like moraines, drumlins, eskers, and kettle lakes. The Great Lakes formed from glacial activity during the Pleistocene epoch.

The hydrologic cycle describes continuous water movement through evaporation, condensation, precipitation, infiltration, and runoff. Approximately 97% of Earth's water is saltwater in oceans; only 3% is freshwater, with most locked in ice caps and glaciers.

Rivers develop drainage patterns based on underlying geology. Dendritic patterns form on uniform rock, trellis patterns on alternating resistant and weak rock, radial patterns on volcanic cones, and rectangular patterns on jointed bedrock. Rivers progress through youthful, mature, and old-age stages, developing features like V-shaped valleys, meanders, oxbow lakes, floodplains, and deltas.

Groundwater occupies pore spaces in soil and rock. The water table marks the upper surface of saturated ground. Aquifers are permeable rock layers that store and transmit groundwater. The Ogallala Aquifer underlies the Great Plains and faces depletion from agricultural irrigation.

Oceans influence climate through heat storage and distribution. Ocean currents operate as surface currents driven by wind and deep currents driven by density differences (thermohaline circulation). The Gulf Stream carries warm water from the Gulf of Mexico northward along the Atlantic coast, moderating Western Europe's climate.

Weather describes short-term atmospheric conditions; climate describes long-term average patterns. Climate is determined by latitude, altitude, proximity to water, ocean currents, prevailing winds, and topography.

Earth's climate zones include tropical (low latitude, warm year-round), temperate (mid-latitude, seasonal variation), and polar (high latitude, cold year-round). The Köppen climate classification system categorizes climates using letters: A (tropical), B (dry), C (temperate), D (continental), and E (polar).

Atmospheric circulation operates through three cells in each hemisphere: Hadley cells near the equator, Ferrel cells in mid-latitudes, and Polar cells near poles. Rising air at the equator creates the Intertropical Convergence Zone with heavy rainfall. Descending air at approximately 30° latitude creates subtropical high-pressure zones and desert belts.

Air masses are large bodies of air with uniform temperature and humidity. Continental polar (cP) air is cold and dry; maritime tropical (mT) air is warm and humid. Fronts form where air masses meet. Cold fronts produce intense, brief precipitation; warm fronts produce prolonged, lighter precipitation; stationary fronts cause extended cloudiness; occluded fronts form when a cold front overtakes a warm front.

Severe weather includes thunderstorms, tornadoes, hurricanes, and blizzards. Tornadoes form from rotating updrafts in severe thunderstorms, primarily in the central United States ("Tornado Alley"). Hurricanes are tropical cyclones with sustained winds exceeding 74 mph, forming over warm ocean water and weakening over land.

Biomes are large ecological communities defined by climate and dominant vegetation. Major terrestrial biomes include tropical rainforest, tropical savanna, desert, Mediterranean, temperate grassland, temperate deciduous forest, taiga (boreal forest), and tundra.

Tropical rainforests occur near the equator with high rainfall and temperatures, supporting the greatest biodiversity. Deserts receive less than 10 inches of annual precipitation and exhibit extreme temperature variation. Temperate grasslands (prairies, steppes) have moderate rainfall insufficient for forests, supporting grasses and grazing animals. Taiga is the largest terrestrial biome, dominated by coniferous trees in cold northern climates. Tundra exists in polar regions and high mountains, characterized by permafrost and low-growing vegetation.

Aquatic biomes include freshwater (lakes, rivers, wetlands) and marine (oceans, coral reefs, estuaries). Wetlands provide flood control, water filtration, and wildlife habitat. Estuaries where rivers meet oceans are highly productive ecosystems serving as nurseries for many marine species.