Rucete ✏ AP Environmental Science In a Nutshell
4. Earth Systems and Resources
This unit covers Earth's dynamic systems including plate tectonics, soil formation, atmospheric layers, wind patterns, watersheds, solar radiation, and major climate phenomena like El Niño and La Niña. Understanding these systems is essential for analyzing environmental processes and resource distribution.
4.1 Plate Tectonics
Theory Overview
• Earth's lithosphere is divided into tectonic plates that move over the mantle.
• Much of Earth's seismic activity occurs at plate boundaries.
Continental Drift (Wegener)
• Pangaea: supercontinent that broke apart ~200 million years ago.
• Evidence includes fossil distribution, glaciation patterns, and rock similarities.
Seafloor Spreading
• New crust forms at mid-ocean ridges, evidenced by symmetrical magnetic patterns and rock age.
Types of Plate Boundaries
• Convergent: plates move toward each other → subduction zones, mountain ranges, trenches (e.g., Himalayas, Cascade Range).
• Divergent: plates move apart → magma upwelling forms ridges, rift valleys (e.g., Mid-Atlantic Ridge, East African Rift).
• Transform: plates slide past each other → earthquakes (e.g., San Andreas Fault).
4.2 Soil Formation and Erosion
Soil Composition
• Ideal loam: 45% minerals (sand, silt, clay), 25% air, 25% water, 5% organic matter.
• Formed through weathering of parent material influenced by climate, organisms, topography, and time.
Erosion and Human Impact
• Caused by wind, water, deforestation, poor agriculture (e.g., monoculture, overgrazing).
• Effects: reduced water retention, nutrient loss, compaction, and increased runoff.
Landslides and Mudslides
• Triggered by rain, earthquakes, volcanoes, and vegetation loss on steep slopes.
Rock Types
• Igneous: from cooling magma (intrusive: granite; extrusive: basalt).
• Metamorphic: heat and pressure (e.g., marble, slate).
• Sedimentary: compacted materials; only type containing fossils.
4.3 Soil Composition and Properties
Soil Horizons (Soil Profile)
• O horizon: organic matter (litter, decomposed leaves).
• A horizon (topsoil): organic material mixed with minerals; crucial for plant growth.
• B horizon (subsoil): accumulation of leached minerals like iron and aluminum.
• C horizon: partially weathered parent material.
• R horizon: bedrock.
Soil Types by Texture
• Sand: large particles, good drainage, poor nutrient retention.
• Silt: medium particles, moderate retention and drainage.
• Clay: smallest particles, high nutrient retention, poor drainage.
• Loam: balanced mix of sand, silt, and clay → ideal for agriculture.
Soil Characteristics
• Permeability: rate at which water passes through soil.
• Porosity: amount of pore space between particles (affects water retention).
• pH: affects nutrient availability (ideal range: 6.0–8.0).
• Fertility: capacity to support plant growth (depends on nutrient content and organic matter).
• Color: darker soils usually indicate higher organic matter.
Soil Degradation
• Caused by erosion, compaction, salinization, nutrient depletion, and contamination.
• Solutions: conservation tillage, cover crops, crop rotation, terracing, contour plowing.
4.4 Earth's Atmosphere
Atmospheric Layers (from lowest to highest)
• Troposphere: weather occurs here; temperature decreases with altitude.
• Stratosphere: contains ozone layer; temperature increases with altitude due to UV absorption.
• Mesosphere: coldest layer; meteors burn up here.
• Thermosphere: thin air; auroras; temperature increases with altitude.
• Exosphere: outermost layer; merges into space.
Atmospheric Composition
• 78% nitrogen, 21% oxygen, 1% other gases (argon, CO₂, methane, etc.).
• Water vapor varies and plays a key role in weather and climate.
Weather vs. Climate
• Weather: short-term atmospheric conditions (e.g., temperature, humidity, precipitation).
• Climate: long-term average of weather over decades.
4.5 Global Wind Patterns
Air Circulation Basics
• Unequal solar heating causes air to rise at the equator and sink at the poles, creating convection cells.
• Warm air rises (less dense), cools, and sinks (more dense), driving wind and weather patterns.
Hadley, Ferrel, and Polar Cells
• Hadley Cells: 0°–30° latitude; warm equatorial air rises, cools, and descends at ~30° N/S.
• Ferrel Cells: 30°–60° latitude; indirect circulation; driven by adjacent cells.
• Polar Cells: 60°–90° latitude; cold air sinks at poles and moves toward 60°.
Surface Winds
• Trade Winds: blow from east to west in tropics (0°–30°).
• Westerlies: blow from west to east in mid-latitudes (30°–60°).
• Polar Easterlies: blow from east to west near poles (60°–90°).
Coriolis Effect
• Caused by Earth's rotation; deflects wind to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
• Responsible for curved wind and ocean current paths.
Jet Streams
• Fast-moving ribbons of air near the top of the troposphere (especially between Hadley and Ferrel cells).
• Influence weather patterns and air travel efficiency.
4.6 Watersheds
Definition
• A watershed is a region of land where all water drains to a common body of water (river, lake, ocean).
• Also called a drainage basin.
Watershed Features
• Includes surface water (streams, rivers, lakes) and groundwater (aquifers).
• Topography (elevation and slope) determines the direction of flow.
• Vegetation, soil, and geology influence water infiltration, runoff, and erosion.
Human Impact
• Urbanization increases impervious surfaces → more runoff and flooding.
• Deforestation and agriculture → increased erosion and sedimentation.
• Pollution from point (pipes) and non-point (runoff) sources can degrade water quality.
Management Practices
• Reforestation, buffer zones, sustainable agriculture, wetland protection, and stormwater management help protect watersheds.
4.7 Solar Radiation and Earth's Seasons
Insolation
• Insolation is incoming solar radiation; it powers Earth's weather, climate, and life processes.
• Greatest at the equator and least at the poles due to Earth's curvature.
• Varies with latitude, season, time of day, and atmospheric conditions.
Earth’s Tilt and Seasons
• Earth is tilted 23.5° on its axis.
• As Earth orbits the sun, this tilt causes seasonal variations in day length and insolation.
• Northern Hemisphere receives more sunlight from March to September; Southern Hemisphere receives more from September to March.
Equinoxes and Solstices
• Equinoxes: March 21 and September 23 → equal day and night; sun is directly above the equator.
• Solstices: June 21 and December 21 → longest and shortest days; sun is directly over Tropic of Cancer or Capricorn.
Albedo Effect
• Albedo is the reflectivity of a surface.
• Ice and snow reflect more sunlight (high albedo), while forests and oceans absorb more (low albedo).
• Affects local and global temperatures.
4.8 Earth’s Geography and Climate
Latitudinal Influence
• Equatorial regions are warm and wet; polar regions are cold and dry.
• Mid-latitudes experience seasonal variation and diverse biomes.
Topography and Rain Shadows
• Moist air rises over mountains, cools, and condenses → precipitation on windward side.
• Dry air descends on leeward side → creates arid rain shadow (e.g., Sierra Nevada → Mojave Desert).
Proximity to Water
• Coastal regions have milder temperatures due to water’s high heat capacity.
• Inland areas have greater temperature extremes (continentality).
Ocean Currents
• Driven by wind, Earth’s rotation, salinity, and temperature differences.
• Redistribute heat across the globe (e.g., Gulf Stream warms Europe).
Climate Zones
• Tropical: hot, high rainfall
• Temperate: seasonal, moderate rainfall
• Polar: cold, dry
4.9 El Niño and La Niña
El Niño–Southern Oscillation (ENSO)
• ENSO is a periodic climate pattern involving changes in Pacific Ocean surface temperatures and atmospheric pressure.
• Occurs every 2–7 years and affects global weather, ecosystems, and economies.
El Niño (Warm Phase)
• Trade winds weaken or reverse, allowing warm water to accumulate off the coast of South America.
• Suppresses upwelling of nutrient-rich water → reduces marine productivity.
• Causes wetter conditions in western South America, drier conditions in Australia and Southeast Asia.
• Increases storm activity in the eastern Pacific; weakens Atlantic hurricane season.
La Niña (Cool Phase)
• Strengthened trade winds push warm water westward, increasing upwelling off South America.
• Leads to cooler ocean temperatures in the eastern Pacific.
• Wetter conditions in Australia and Southeast Asia; drier in the western Americas.
• Can enhance Atlantic hurricane activity.
Global Impacts of ENSO
• Alters precipitation patterns, agricultural productivity, and fish populations.
• Causes flooding, droughts, and economic disruption around the world.
• ENSO events are monitored via ocean buoys and satellite systems.
In a Nutshell
Earth’s systems—including its geologic, atmospheric, and oceanic processes—interact to shape climate, weather, and resource distribution. Plate tectonics and soil formation drive terrestrial landscapes, while global wind patterns and ocean currents influence weather and climate. Solar radiation, seasons, and geographic features regulate temperature and precipitation. Understanding watersheds, ENSO cycles, and soil dynamics is essential for managing ecosystems, predicting climate trends, and conserving Earth’s resources.