Barron's
4.1 Plate Tectonics
Plate tectonic theory: Earth’s lithosphere is divided into plates that travel over the mantle, with Earth’s seismic activity at the boundaries, arose from continental drift and seafloor spreading
Continental drift theory: Wegener proposed that all continents formed from Pangaea and broke down, supported by fossils and landscapes
Seafloor spreading theory: Volcanic rift zones show subduction zones
Types of Boundaries
Convergent boundaries: Two plates slide toward each other, forming a subduction zone, orogenic belt (mountains), or oceanic trench
Divergent boundaries: Two plates slide apart form each other, filled with molten magma, create massive fault zones in the oceanic ridge system or continental rift valleys
Oceanic divergent boundary: Mid-Atlantic Ridge
Continental divergent boundary: East African Great Rift Valley
Island arc: Converging oceanic plates that form volcanic islands by subduction
Transform boundaries: Plates slide past each other, generating friction and stress, like the San Andreas fault
4.2 Soil Formation and Erosion
Soil: Thin layer on top of Earth’s land surface, affects chemistry of ground and surface water, holds nutrients and water, filters water
Soil composition: Minerals, open spaces of air and water, organic materials
Loam: Optimal soil composition for plants, 45% minerals, 5% organic, 25% air, 25% water
Soil Profile
O Horizon: Surface litter of leaves and debris, thick in forests, thin in tundras
A Horizon: Topsoil with organic matter (humus), living organisms, inorganic minerals, thick in grasslands
E Horizon: Zone of leaching, dissolved and suspended materials move downward
B Horizon: Subsoil that tends to be yellowish in color due to accumulation of iron, aluminum, humic compounds, and clay leached from A&E, rich in nutrients where rainwater leached nutrients from topsoil
C Horizon: Weathered parent material from partially broken-down inorganic minerals
Soils develop in response to: climate, living organisms, parent material, topography
Soil Erosion: Movement of weathered rock and soil components by water, wind, human activity, which decreases water-holding capacity because of destruction of soil profile and increase in soil compaction
Soil erosion is caused by: improper plowing, monoculture, overgrazing
Landslides and mudslides
Landslides: Masses of rock, earth, debris move down a slope
Causes of landslides: Heavy rains, droughts, earthquakes, volcanic eruptions, develop when water rapidly collects in the ground
Mudslides: Fast-moving landslide that flows in channels
Causes of mudslides: Steep slopes triggered by natural disasters where wildfires or construction destroyed vegetation, heavy rain
Areas likely to experience landslides: surface runoff, wildfires or construction that destroyed vegetation, channels along stream, slopes altered for construction, steep slopes, where landslides have previously occurred
Rock Types
Igneous rock: Cooling and classified by silica content, broken down by weathering and water transport, create most soils
Intrusive igneous rocks: Solidify deep underground, cool slowly, large-grained texture (e.g. granite)
Extrusive igneous rocks: Solidify on or near the surface, cool quickly, fine-grained smooth texture (e.g. basalt)
Metamorphic rock: Formed by intense heat and pressure, high quartz content (e.g. gneiss), like diamond, marble, or slate
Sedimentary rock: Formed by the piling and cementing of materials like weathered chemical precipitates or fragments of older rocks over time in low-lying areas, fossils form only in this rock
4.3 Soil Composition and Properties
Soil texture: Relative abundance of sand, silt, and clay
Gravel: Coarse particles, consists of rock fragments
Sand: Sedimentary material coarser than silt, water flows through too quickly for most crops, good for crops requiring low amounts of water
Silt: Sedimentary material consisting of very fine particles between sand and clay, easily transported by water
Clay: Very fine particles, compacts easily, forms large dense lumps when wet, low permeability to water, becomes waterlogged easily
Humus: Dark organic material that forms in soil when plant/animal matter decay
Soil with humus: Crumbly, allowing air and water to move easily through this loose soil, making root growth easier, reducing erosion, stabilizing pH
Soil Quality
Aeration: How well a soil is able to absorb oxygen, water, and nutrients. Reduces soil compaction, perforating soil with small holes to allow air, water, and nutrients to penetrate to the roots
Degree of soil compaction: Number of pores affect water infiltration and drainage
Nutrient-holding capacity: Ability of soil to absorb and retain nutrients to be available to the roots of plants, clay is better able to retain nutrients, but highly weathered soils will lose nutrients due to leaching.
Primary plant nutrients: Nitrogen, phosphorus, potassium
Permeability: Measure of capacity of soil to allow water and oxygen to pass through it.
Low permeability: Leads to soil salinization (accumulation of salts)
pH: Measure of how acidic or basic a soil is
Acidic soils: Areas of high rainfall, acid rain, mine spoiling
Basic soils: High amount of potassium, calcium, magnesium, or sodium ions
Pore size: Space between soil particles, determines how much water, air, nutrients available for plant roots
Size of soil particles: Determines amount of moisture, nutrients, and oxygen that soil can hold along with capacity for water to infiltrate
Water-holding capacity: Controlled by soil texture and organic matter content, reflecting particle size distribution, excess will leach downward in soil profile
Water-Holding Capacity and Soil
Amount of soil water available to plants: Depth of soil that roots can explore (root zone), nature of soil material (soil porosity), size of soil particles (texture), arrangement of particles (structure)
Sandier soils need to be irrigated more frequently than clay soils
4.4 Earth’s Atmosphere
Early History
Great Oxidation Event: Rise in oxygen, photosynthesizing unicellular microbes (cyanobacteria), caused mass extinction by triggering ice ages (weakening GHG) and biological diversification and changes in nature of chemical reactions
Current atmospheric composition: Nitrogen, oxygen, water vapor, carbon dioxide
Structure
Troposphere: Lowest portion of atmosphere, 0-10 km above surface, 75% of mass and all water vapor, where weather occurs. Atmospheric pressure highest at the surface and decreases with height. Temperature decreases with height.
Stratosphere: 10-50 km above Earth’s surface, oxygen absorbs UV rays into oxygen. Temperature increases with altitude.
Weather and Climate
Weather: Caused by the movement or transfer of heat energy from unequal heating of Earth’s surface.
Convection: Primary way energy is transferred from hotter to colder regions in Earth’s atmosphere and primary determinant of weather patterns. Latitudinal differences in surface temperature create global-scale flow of energy
Heat index: Measure of how warm it feels when factoring in relative humidity
Climate: Average weather in a geographic region over a period of time
Air mass: Large body of air that has similar temperature and moisture content
Albedo: Reflectivity. Ocean water is low, dust and ice is high
Carbon Cycle: Production of CO2 is exothermic reaction, which results in warming. Both carbonate formation in the oceans and the breakdown of carbonate yield CO2.
Distance to oceans: Thermally more stable than landmasses, specific heat (heat-holding capacity) 5 times greater than air, so milder climates
Fronts: The boundary where two air masses meet (vary in temperature, dew point, wind direction).
Dew Point: Temperature below which water droplets begin to condense
Cold Front: Leading edge of advancing mass of cold air, thunderhead clouds, high surface winds, thunderstorms. Cloud formation and precipitation from uplift of dense, warmer air.
Warm Front: Boundary between advancing warm air mass and cooler one it’s replacing. Less chance of uplift means lower risk of rainfall.
Stationary Front: Pair of air masses remain in same area for long period of time.
Greenhouse Effect
Greenhouse gases: Water vapor, carbon dioxide, methane, nitrous oxide
Heat (convection): How heat energy is exchanged between air over oceans and air over land
Insolation differences: At poles, sun’s rays strike Earth at an acute angle, which spreads heat over a larger area. More heat is lost to the atmosphere, as the rays travel a longer distance through atmosphere.
Moisture content of air: Primary determinant of plant growth and distribution, biome type, atmospheric water vapor creates clouds and rainfall, significant role in energy exchanges in atmosphere.
4.5 Global Wind Patterns
Land and Sea Breezes
Land Breeze: During relatively calm clear nights when land cools down faster than the sea, so air above land is denser than air above sea, so air moves from land toward the coast
Atmospheric Circulation-Pressure
Global air circulation: Affected by uneven heating of Earth’s surface, seasons, the Coriolis effect, the amount of solar radiation reaching Earth over long periods of time, convection cells created by warm ocean waters that commonly lead to hurricanes, ocean currents
Low-pressure weather system: Lower pressure at its center than in areas around it, air rises, water vapor condenses, forming clouds and precipitation
High-pressure weather system: Higher pressure at center than areas around it, winds blow away from high pressure, swirl in opposite direction as those of low-pressure (clockwise north of equator), air from higher sinking down, fair weather
Trade winds: Prevailing pattern of easterly surface winds found in tropics near Earth’s equator, within troposphere or lower portion of Earth’s atmosphere, strengthened during winter
Wind speed: Determined by pressure differences between air masses, measured with anemometer
Wind direction: Based on direction from which it originated (easterly, weasterly), measured with wind vane
Coriolis Effect: Causes prevailing winds in the Northern Hemisphere to spiral clockwise out from high-pressure areas and counterclockwise toward low-pressure areas. Due to Earth’s rotation on its axis that causes winds to not travel straight. Amount of deflection related to the speed at which air is moving and latitude.
The Cells
Hadley Air Circulation Cells: Air heated at equator rises, cools in upper atmosphere, then sinks back to surface within subtropical climate zone. Equator has high humidity, clouds, rains, tropical rainforest, temperature varies day to night. Subtropical regions have low relative humidity, cloud formation, high ocean evaporation, deserts, hot summers, mild winters.
Ferral Air Circulation Cells: 30-60, mid-latitude climates have severe winters, cool summers, drier, tropical and polar air masses, defined seasons, deciduous evergreen forests
Polar Air Circulation Cells: Icy-cold, dry, dense air that descends from troposphere to ground, meets with warm tropical air from mid-latitudes, then sinks, which suppresses precipitation. Severe winters, small precipitation in short summers. Tundra and taiga.
Polar Vortex: Low-pressure zone embedded in mass of cold air on top of poles, strengthen in winters, weaken in summers.
Relationship between Antarctic polar vortex and severe ozone depletion. Chlorine concentrations build up.
Hurricanes, Tornadoes, Monsoons
Hurricanes, cyclones, typhoons are all the same weather phenomenon.
Caused by a pre-existing weather disturbance, warm tropical oceans, atmospheric moisture, relatively light winds in the upper troposphere.
Combine to produce violent winds, very large waves, torrential rains, and floods.
Most severe weather phenomenon on the planet.
Begin over warm oceans in areas where the trade winds converge.
Subtropical high-pressure zone creates hot daytime temperatures with low humidity that allow for large amounts of evaporation, with the Coriolis effect initiating the cyclonic flow.
Cyclonic circulation allows picking up of moisture and latent heat energy from ocean.
Eye of the hurricane is an area of descending air and low pressure.
The energy of a hurricane dissipates as it travels over land or moves over cooler bodies of water.
Storm surge: Rise in sea level that occurs during tropical cyclones, typhoons, or hurricanes.
Tornadoes: Swirling masses of air with wind speeds close to 300 miles per hour.
Center of the tornado is an area of low pressure.
Formed from a single convective storm, in contrast to many convective storms that form hurricanes.
Require substantial vertical shear of the horizontal winds, as opposed to low values like hurricanes.
Monsoons: Strong, violent winds that change direction with season. Blow from cold to warm regions because cold air takes up more space than warm air. Blow from the land toward the sea in winter. andfrom the sea toward land in the summer.
4.6 Watershed
Watershed: Area of land that drains water from rainfall and snowmelt into a specific body of water or allows it to seep into the ground and collect in underground reservoirs known as aquifers.
Watershed management: Use of land, forest, and water resources to not harm biosphere, such as reducing pesticides and fertilizers that wash off farm fields into bodies of water.
4.7 Solar Radiation and Earth’s Seasons
Angle of sunlight: Varies by location, time of day, and season.
Lower angle: Sun is closer to the horizon, the energy of the sunlight spreads out over a larger area and is therefore weaker (winter). Sunlight must pass through more atmosphere, which causes diffraction and a reduction in amount of sunlight that reaches surface.
Solar intensity: Tilt of Earth’s axis (23.5 degrees), atmospheric conditions, Earth’s rotation around the sun (once per year), Earth’s rotation on its axis (once every 24 hours)
4.8 Earth’s Geography and Climate
Climate: Prevailing patterns of temperature and precipitation in a defined region on Earth
Weather: Condition of the atmosphere in one area at a particular time
Function of water: Oceans and lakes store solar radiation (heat), adds moisture to the air above it, drives major air currents, stabilizes climate of land masses by absorbing extra heat and releasing during cooler periods. Warm, moist ocean air drives precipitation patterns.
Higher elevations: Lower air pressure, cooler temperatures, more precipitation, deserts due to location on the downwind side of a mountain range (rain shadow).
Mountain ranges: Barriers to the smooth movement of air currents across continents. When an air masses encounters, it’s slowed and cooled because air is forced up into atmosphere and can’t hold as much moisture, so it releases as precipitation.
4.9 El Nino and La Nina
La Nada: Normal conditions where easterly trade winds move water and air toward the west. Ocean is higher and warmer in the western pacific.
The trade winds make a deep warm layer in the west that pushes the thermocline down while it rises in the east.
Upwelling: Shallow thermocline allows winds to pull nutrient-rich water from below, increasing fishing stocks.
Occur when prevailing winds, produced through Coriolis effect and moving clockwise in the Northern Hemisphere, push warmer, nutrient-poor surface waters away from the coastline. Nutrients are supplied for phytoplankton.
El Nino: The warm phase. Air pressure patterns reverse direction → trade winds decrease in strength → thermocline off western South America becomes deeper, decrease in upwelling of nutrients (fish kills) → Warmer water temperatures
Strongest during the Northern Hemisphere winter because ocean temperatures worldwide are warmest.
Enhances convection, alters the jet stream, which enhances precipitation across western and southern US, and winteer temperatures are cooler.
La Nina: The cool phase. Westerlies across the tropical Pacific are strong → Increase in upwelling off South America → Cooler sea surface temperatures off South America, wetter in Pacific Northwest, warmer in Southern → Increases number of hurricanes.
Warmer or cooler ocean temperatures: Decrease in upwelling, coral reefs, migration/weather patterns, CO2, marine biodiversity, hurricanes/tornadoes, glacial melting.
Increase or decrease in rainfall: Reduced agricultural output, changes in migration patterns, starvation, extinction, forest fires, water shortages, flooding, soil erosion, leaching.