Physical Geography Flashcards

Earth Structure and Planetary Spheres

• Crust: The thin, solid outermost layer where humans, plants, and animals live. Its thickness ranges from $0\,\text{km}$ to $100\,\text{km}$.
  • Continental Crust: Thicker and less dense.
  • Oceanic Crust: Thinner and denser.
• Mantle: A thick layer located directly beneath the crust, composed of hot, semi-solid rock. Convection movement of material in the mantle helps drive plate tectonics.
• Outer Core: A liquid layer composed primarily of liquid iron and nickel extending from a depth of $2900\,\text{km}$ to $5100\,\text{km}$. The movement of liquid metal in this layer generates Earth's magnetic field.
• Inner Core: The solid innermost sphere extending from $5100\,\text{km}$ to Earth's center at $6378\,\text{km}$. It is composed of solid iron and nickel and remains solid despite extreme temperatures due to massive overburden pressure.

• Earth's Four Spheres:
  • Atmosphere: The protective envelope of gases surrounding Earth.
  • Hydrosphere: All water present on Earth, including oceans, rivers, lakes, groundwater, glaciers, and atmospheric water vapor.
  • Lithosphere: The solid outer layer of Earth, comprising the crust and the uppermost solid mantle.
  • Biosphere: All regions of Earth where living organisms exist.
• Spherical Interactions: The four spheres interact continuously. For instance, precipitation from the atmosphere enters the hydrosphere, providing essential moisture that sustains life within the biosphere.

Plate Tectonics and Boundary Dynamics

• Theory of Plate Tectonics: The scientific theory stating that Earth's lithosphere is divided into several large, rigid plates that move slowly across the underlying asthenosphere.
• Drivers of Plate Motion:
  • Convection currents operating within the thermal mantle.
  • Internal heat energy originating from Earth's core.
  • Ridge push at mid-ocean spreading ridges.
  • Slab pull at subduction zones.

• Major Tectonic Plates: North American Plate, Eurasian Plate, Pacific Plate, Juan de Fuca Plate, Philippine Plate, Indo-Australian Plate, Cocos Plate, Nazca Plate, Caribbean Plate, South American Plate, African Plate, Arabian Plate, Scotia Plate, and Antarctic Plate.

• Constructive / Divergent Boundaries:
  • Motion: Two plates move away from each other.
  • Effect: Constructive process where new oceanic lithosphere is created.
  • Topography & Features: Mid-ocean ridges, rift valleys, new crust, volcanoes, and shallow earthquakes.
  • Example: The Mid-Atlantic Ridge.
• Destructive / Convergent Boundaries:
  • Motion: Two plates collide or move toward each other.
  • Effect: Destructive process where oceanic lithosphere is consumed or subducted.
  • Oceanic + Continental Convergence: The denser oceanic plate subducts beneath the lighter continental plate into the subduction zone. Produces deep ocean trenches, continental volcanic arcs, fold mountains, and intense earthquakes.
  • Oceanic + Oceanic Convergence: One oceanic plate subducts beneath another, creating deep ocean trenches, volcanic island arcs, and earthquakes.
  • Continental + Continental Convergence: Neither continental plate subducts due to low density. The crust buckles, compresses, and folds. Produces vast fold mountain ranges and frequent earthquakes. Example: The Himalayas.
• Conservative / Transform Boundaries:
  • Motion: Plates slide laterally past one another.
  • Effect: Conservative process where lithosphere is neither created nor destroyed.
  • Topography & Features: Transform faults, severe earthquakes within the crust, and an absence of major volcanic activity.

Volcanology

• Definition: An opening or vent in Earth's crust through which magma, volcanic gases, and ash escape to the surface.

• Types of Volcanoes:
  • Shield Volcano: Broad, gently sloping structure built by successive flows of low-viscosity, runny lava. Generally characterized by non-explosive eruptions.
  • Composite Volcano / Stratovolcano: Tall, steep-sided cone constructed from alternating layers of hardened lava, tephra, and volcanic ash. Capable of highly explosive and hazardous eruptions.
  • Cinder Cone: Small, steep-sided volcano formed primarily from accumulated pyroclastic fragments and scoria.
  • Fissure Volcano: An elongated crack in the crust through which lava erupts across a wide line.
  • Lava Dome: A steep mound formed by viscous lava that accumulates near the eruption vent.
  • Caldera Volcano: A large, basin-shaped depression formed when a volcano collapses into its emptied magma chamber.
• Geographic Distribution: Volcanoes occur predominantly along active plate boundaries, along the Pacific Ring of Fire, at mid-ocean divergent ridges, within oceanic subduction zones, and over intraplate mantle hotspots.

Landforms, Weathering, and Erosion

• Classification of Major Landforms:
  • Mountains: Elevated landforms featuring steep slopes. Includes fold mountains, block mountains, volcanic mountains, and dome mountains.
  • Plateaus: Elevated regions characterized by flat or gently undulating terrain.
  • Plains: Large, low-lying stretches of flat land.
  • Valleys: Low terrain situated between hills or mountain ranges.
  • Canyons / Gorges: Deep, narrow valleys with steep, cliff-like sides.
  • Coastal Landforms: Features produced by wave energy, including cliffs, headlands, caves, arches, stacks, beaches, sand dunes, spits, bars, lagoons, and tombolos.

• Weathering: The process of fracturing and breaking down rocks in situ (in their original location).

• Physical / Mechanical Weathering: Mechanical breakdown of rocks without altering chemical composition.
  • Frost Wedging: Water penetrates cracks, freezes, expands, and forces rock apart.
  • Thermal Expansion: Diurnal temperature changes cause expanding and contracting cycles that induce fracturing.
  • Exfoliation: Outer rock layers peel away due to pressure release.
  • Salt Weathering: Salt crystals grow within pore spaces, exerting internal pressure.
  • Abrasion: Mechanical scraping of rock surfaces by wind-blown or water-borne particles.
• Chemical Weathering: Decomposes or dissolves minerals within rock structures.
  • Carbonation: Weak carbonic acid dissolves susceptible minerals.
  • Oxidation: Reaction between atmospheric oxygen and iron-bearing minerals, generating rust.
  • Hydrolysis: Reaction between water molecules and rock minerals, breaking them down into new mineral compounds.
  • Solution / Acid Rain: Acidified rainfall dissolves mineral compounds.
• Biological Weathering: Disintegration caused by living organisms.
  • Plant Roots: Roots grow into rock crevices, expanding and exerting mechanical pressure.
  • Burrowing Animals: Excavation destabilizes substrate and increases air/water exposure.
  • Lichens: Organisms secrete organic acids that decompose mineral surfaces.
• Erosion: The breakdown, detachment, and downslope transportation of surface material.
  • Hydraulic Action: The force of moving water dislodges particles from surfaces.
  • Abrasion / Corrasion: Sediments carried by water, wind, or glacial ice scrape across rock surfaces.
  • Attrition: Particles transported by moving water crash into one another, becoming smaller and rounder.
  • Solution / Corrosion: Soluble mineral matter is dissolved into fluid solutions.
  • Agents of Erosion: Running water (rivers/streams), ocean waves, wind action, glacial ice, and gravitational mass movement.

River Systems and Profiles

• Anatomy of a River System:
  • Source: The originating point of a river.
  • Tributary: A smaller stream or river feeding into a main river channel.
  • Confluence: The junction point where two watercourses meet.
  • River Channel: The structural bed and banks through which water flows.
  • Meander: A pronounced bend or curve in a river channel.
  • Floodplain: Flat land adjacent to a river formed by sediment deposition during floods.
  • Oxbow Lake: A crescent-shaped lake formed when a meander neck is breached and cut off.
  • Mouth: The terminus where a river enters a sea, lake, or larger body of water.
  • Estuary: A partially enclosed coastal river mouth where freshwater mixes with ocean saltwater.
  • Delta: A landform created by sediment deposition at a river mouth.

• Three Courses of a River Profile:
  • Upper Course (Youthful Stage): Features steep gradients, high kinetic energy, and dominant vertical erosion. Characteristics include deep narrow channels, V-shaped valleys, interlocking spurs, waterfalls, rapids, and gorges.
  • Middle Course (Mature Stage): Characterized by moderate gradients, balanced lateral erosion and sediment transport, wider channel capacity, increased discharge, meanders, cut banks, point bars, and developing floodplains.
  • Lower Course (Old Stage): Low energy, gentle gradients, and dominant sediment deposition. Landforms include wide floodplains, expansive meanders, oxbow lakes, natural levees, and deltas with distributary channels or estuaries.

Oceanography and Meteorology

• Ocean Currents: Continuous, directed movements of seawater.
  • Forcing Factors: Global wind belts, thermal gradients, salinity differences, Coriolis effect from Earth's rotation, and continental configurations.

*   **Warm Currents**: Transport warm equatorial waters poleward toward higher latitudes (e.g., Gulf Stream, North Atlantic Drift, Kuroshio Current, East Australia Current).
*   **Cold Currents**: Move cold polar water equatorward toward lower latitudes (e.g., California Current, Peru Current, Benguela Current, Canaries Current, West Wind Drift).
*   **Climatic & Environmental Impacts**: Regulate atmospheric heat transport, modify coastal climate regimes, alter precipitation patterns, and enhance marine fisheries through upwelling.

• Atmospheric Pressure Systems:
  • Definition: Pressure exerted on Earth's surface by the gravitational weight of the air column above.

*   **High-Pressure Systems**: Cool air sinks toward the surface, creating high pressure. Winds blow outward from high-pressure cells, producing clear, dry, and stable weather.
*   **Low-Pressure Systems**: Warm air expands and rises, creating surface low pressure. Converging inward winds cool and condense, producing clouds and precipitation.

• Global Pressure Belts and Planetary Winds:
  • Equatorial Low-Pressure Belt: Located around $0^\circ$.
  • Subtropical High-Pressure Belts: Located near $30^\circ\,\text{N}$ and $30^\circ\,\text{S}$.
  • Subpolar Low-Pressure Belts: Located near $60^\circ\,\text{N}$ and $60^\circ\,\text{S}$.
  • Polar High-Pressure Belts: Located at $90^\circ\,\text{N}$ and $90^\circ\,\text{S}$.
  • Prevailing Wind Belts: N.E. and S.E. Trade Winds, S.W. and N.W. Westerlies, N.E. and S.E. Polar Winds.

• Precipitation Mechanisms:
  • Convectional Rainfall: Solar radiation heats the ground, warming the air above it. The warm air rises, expands, cools, and condenses into cloud formations, generating intense convective rainfall (common in tropical latitudes).
  • Relief / Orographic Rainfall: Moist maritime air is forced upward over topographical barriers like mountain ranges. Rising air cools to saturation, causing condensation and heavy precipitation on the windward side, while creating a dry rain shadow region on the leeward side.
  • Frontal / Cyclonic Rainfall: Occurs along boundary fronts where warm air masses encounter denser cold air masses. The warm air is forced upward over the cold air, cooling and condensing into widespread precipitation.

Coordinates, Astronomical Motions, and Climate Dynamics

• Geographic Coordinate System:
  • Latitude: Measures angular distance north or south of the Equator.

*   **Equator**: $0^\circ$
*   **Tropic of Cancer**: $23.5^\circ\,\text{N}$
*   **Tropic of Capricorn**: $23.5^\circ\,\text{S}$
*   **Arctic Circle**: $66.5^\circ\,\text{N}$
*   **Antarctic Circle**: $66.5^\circ\,\text{S}$
*   **North Pole**: $90^\circ\,\text{N}$
*   **South Pole**: $90^\circ\,\text{S}$

• Planetary Motions:
  • Rotation: Earth rotates on its tilted axis from west to east once every $24\,\text{hours}$, causing day and night.
  • Axial Tilt: Earth's axis is inclined at an angle of $23.5^\circ$. This tilt causes seasonal variation, changes in daylight duration, and shifting solar elevation angles throughout the year.
• Gravitational Forces: Gravity holds atmospheric gases around Earth, maintains surface placement, drives liquid streamflow downslope, and induces mass movements.
• Factors Regulating Climate: Latitude, altitude, continentality (distance from oceans), ocean currents, topographic relief, and prevailing wind directions.

Biomes and Forest Ecosystems

• Major Global Biomes:
  • Tropical Rainforest: Hot, humid equatorial zones with dense, multi-layered evergreen forests and high biodiversity.
  • Savanna: Warm tropical biome characterized by seasonal rainfall, expansive grasslands, and scattered drought-resistant trees.
  • Desert: Arid regions receiving minimal precipitation, supporting sparse xerophytic vegetation.
  • Temperate Grassland: Mid-latitude interior regions featuring moderate precipitation and grass cover.
  • Temperate Deciduous Forest: Mid-latitude regions with moderate temperatures and seasonal broadleaf trees that shed leaves in winter.
  • Coniferous / Boreal Forest (Taiga): Cold subarctic regions dominated by evergreen coniferous species.
  • Tundra: Polar regions characterized by extreme cold, permafrost, and low-growing vegetation.
  • Other Biomes: Mediterranean vegetation / Chaparral and mountain vegetation systems.

• Forest Stratification:
  • Emergent Layer: The highest vertical layer containing giant trees that rise above the canopy. Receives intense sunlight and strong wind forces; inhabited by specialized birds, bats, insects, and primates.
  • Canopy Layer: A continuous overhead roof created by interlocking crowns of tall trees. Receives abundant light and harbors the majority of forest wildlife.
  • Understory Layer: Shaded environment beneath the canopy containing saplings, shrubs, and woody vines. Characterized by low light, high humidity, and warm temperatures.
  • Forest Floor: The dark ground surface where leaf litter and organic matter accumulate. Saprophytes and decomposers (fungi, bacteria, insects) recycle nutrients back into the soil matrix.
• Forest Biome Formations:
  • Tropical Rainforest: Continuously warm and wet equatorial systems (e.g., Amazon, Congo, Southeast Asia).
  • Tropical Monsoon Forest: Seasonal climate with distinct wet and dry phases; deciduous species shed foliage during drought periods.
  • Temperate Deciduous Forest: Found in Europe, North America, and Eastern Asia, characterized by seasonal leaf shedding.
  • Coniferous / Boreal Forest: Expansive high-latitude belts dominated by needle-leaf evergreen conifers.

Soil Science and Horizons

• Soil Profile: A vertical cross-section of soil revealing distinct horizontal strata (horizons).

• Master Soil Horizons:
  • O Horizon: Surface organic horizon composed of partially decomposed organic detritus, fallen leaves, and humus.
  • A Horizon (Topsoil): Fertile dark horizon rich in accumulated organic humus, active plant roots, and biological organisms.
  • E Horizon (Eluviation Layer): Light-colored zone depleted of mineral clays, iron, or organic matter by downward leaching.
  • B Horizon (Subsoil): Illuvial accumulation zone where leached minerals, clays, and iron oxides precipitate.
  • C Horizon (Parent Material): Layer of unconsolidated, partially weathered parent rock fragment material.
  • R Horizon (Bedrock): Unweathered, solid parent rock layer.

Economic Sectors, Mining, and Energy

• Industrial Sector Categorization:
  • Primary Industry: Direct extraction and harvesting of raw natural resources (e.g., agriculture, forestry, commercial fishing, mining).
  • Secondary Industry: Manufacturing and construction processes that convert raw inputs into processed goods (e.g., heavy manufacturing, food processing, textile production).
  • Tertiary Industry: Commercial and public service provision (e.g., banking, transport, retail, healthcare, education, tourism).
  • Quaternary Industry: Knowledge-based intellectual activities (e.g., scientific research, information technology, data analysis).
• Industrial Location Factors: Availability of raw materials, labor force, energy supply, transport networks, market access, financial capital, suitable land, government regulations, and water supply.

• Mining Extraction Methods:
  • Open-Pit / Open-Cast Mining: Excavation of vast surface pits used for deposits located near the surface.
  • Strip Mining: Sequential removal of overburden strips to expose shallow mineral seams (e.g., coal).
  • Underground / Shaft Mining: Vertical shafts and horizontal tunnels constructed deep underground to extract buried ores.
  • Alluvial Mining: Hydraulic separation of heavy mineral grains (e.g., gold) from river gravels and sediments.
  • Quarrying: Open surface cutting of dimensional stone, rock, and aggregates (e.g., limestone, granite, gravel).
• Natural Resources:
  • Renewable Resources: Resources naturally replenished on human timescales (e.g., solar radiation, wind energy, water, managed forests, fish stocks).
  • Non-Renewable Resources: Finite resources formed over geological periods (e.g., fossil fuels like coal, oil, natural gas; mineral ores like gold, copper).
• Energy Resource Drivers: Geographic distribution depends on geological history, localized climate, water accessibility, wind currents, solar irradiance, and fossil fuel basins.

Greenhouse Gases and Global Climate Change

• The Greenhouse Effect: The natural atmospheric mechanism where greenhouse gases absorb outgoing longwave thermal radiation emitted by Earth, maintaining global surface temperatures.
• Principal Greenhouse Gases: Carbon dioxide ($\text{CO}_2$), Methane ($\text{CH}_4$), Nitrous oxide ($\text{N}_2\text{O}$), Water vapor ($\text{H}_2\text{O}$), and Ozone ($\text{O}_3$).
• Human Drivers: Fossil fuel combustion, deforestation, agricultural activities, industrial processes, transportation, and landfill organic waste decomposition.
• Environmental Consequences: Global warming, climate destabilization, polar ice cap and glacial retreat, global sea-level rise, altered precipitation patterns, and increased frequency of extreme weather events.

Demography and Urban Geography

• Population Pyramids:

*   **Expanding Pyramid**: Broad base reflecting high birth rates, rapid population growth, and high youth proportions (e.g., Cambodia 2014, Philippines 2017).
*   **Stable Pyramid**: Uniform age distribution reflecting balanced birth and death rates and slow growth.
*   **Contracting Pyramid**: Narrow base reflecting low birth rates, an aging population, and slow or negative growth.

• Urban Structure Models:

*   **Concentric Zone Model**: Cities grow outward in concentric rings from the core: 1. Central Business District (CBD), 2. Zone of transition / Light manufacturing, 3. Low-class residential, 4. Medium-class residential, 5. Commuter zone.
*   **Sector Model**: Urban land uses expand outward along major transportation corridors in wedge-shaped sectors.
*   **Multiple Nuclei Model**: Cities develop around several distinct growth nodes or nuclei rather than a single CBD.

• Urban Dynamics:
  • Urbanisation: Growth in the proportion of people living in urban areas, driven by rural-to-urban migration and industrial development.
  • Informal Settlements / Shanty Towns: Unplanned settlements lacking formal property rights, characterized by high density, poor housing, inadequate sanitation, and limited infrastructure.
  • Urban Decay: Physical, economic, and social deterioration of urban areas due to disinvestment and depopulation.
  • Urban Renewal: Redevelopment of decaying urban areas through infrastructure investment, housing rehabilitation, and commercial revival.
  • Gentrification: Inflow of higher-income residents and capital investment into low-income urban neighborhoods, leading to rising property values and displacement risks for lower-income residents.
• Solid Waste Management: Methods include Landfills, Incineration, Mechanical Recycling, Biological Composting, and Waste Reduction.

Biogeography and Ecosystem Structure

• Taxonomic Classification of Fauna:
  • Marine Organisms: Fish (gill respiration; e.g., salmon, tuna, sharks), Marine Mammals (lung respiration; e.g., whales, dolphins, seals), Marine Reptiles (e.g., sea turtles, sea snakes), Molluscs (e.g., octopus, squid), Crustaceans (e.g., crabs, lobsters), and Cnidarians (e.g., jellyfish, corals).
  • Terrestrial Organisms: Mammals (endothermic, fur/hair, feed young milk), Birds (feathers, lay eggs), Reptiles (ectothermic, scaly skin), Amphibians (dual aquatic/terrestrial phases), Insects (six legs, three body divisions), and Arachnids (eight legs).
• Ecosystem Energetics:

*   **Food Chain Sequence**: Linear transfer of energy: Primary Producer (Grass) $\rightarrow$ Primary Consumer (Grasshopper) $\rightarrow$ Secondary Consumer (Frog) $\rightarrow$ Tertiary Consumer (Snake) $\rightarrow$ Apex Consumer (Hawk).
*   **Food Web**: Interlocking network of multiple food chains within an ecosystem.
*   **Trophic Levels**: Producers (autotrophs), Primary Consumers (herbivores), Secondary Consumers (carnivores), Tertiary Consumers, and Decomposers (bacteria/fungi).
*   **Energy Pyramid Principles**: Available energy decreases exponentially at higher trophic levels. Most energy is lost between levels through metabolic respiration, kinetic movement, excretion, and thermal heat loss.