APES UNIT 4

Continental Drift

Proposed by Alfred Wegener (1915)

🌍 Pangaea: A supercontinent that began breaking apart 200 million years ago.

🔍 Evidence for Continental Drift:
1⃣ Fossils of extinct land animals on separate continents.
2⃣ Fossilized tropical plants under Greenland’s ice caps.
3⃣ Glaciated landscapes in the tropics (Africa & South America).
4⃣ Rock similarities between America’s east coasts and Africa & Europe’s west coasts.
5⃣ Continents fit together like puzzle pieces.
6⃣ Past polar climates in tropical regions (paleo-climatic data).

Seafloor Spreading Theory (1960s)

🌊 Key Discoveries:

• Alternating magnetic patterns in oceanic rocks.

• Rocks near mid-ocean ridges are younger; older farther away.

• Suggests new crust is formed at volcanic rift zones.

Lithosphere & Plate Movement

🌍 The lithosphere is the solid outer layer of Earth.
🛑 Plates move slowly, causing earthquakes and volcanoes.

🔽 Subduction Zones:

• Areas where one tectonic plate moves under another.

• Causes volcanoes and earthquakes.

1⃣ Convergent Boundaries (➡⬅)

• Plates move toward each other.

• Creates:

  • Subduction zones (one plate moves under another).

  • Orogenic belts (if plates collide and compress).

• Example: Cascade Mountain Range.

🔽 When Oceanic & Continental Plates Converge:

• Denser oceanic plate subducts beneath the continental plate.

• Forms oceanic trenches & mountain ranges.

🏝 When Two Oceanic Plates Converge:

• Forms an island arc (volcanic islands).

• A deep-sea trench forms at the subduction zone.

🏔 When Two Continental Plates Converge:

• Mountain ranges form as plates compress & push up.

2⃣ Divergent Boundaries (⬅➡)

• Plates move apart.

• Forms fault zones & oceanic ridges.

• Frequent earthquakes occur.

🌊 Examples:

• Mid-Atlantic Ridge (Oceanic Divergent Boundary).

• East African Great Rift Valley (Continental Divergent Boundary).

3⃣ Transform Boundaries (⬆⬇)

• Plates slide past each other in opposite directions.

• Friction & stress buildup cause earthquakes.

• Example: San Andreas Fault.

Soil

🟤 Definition: A thin layer on Earth’s land surface that is a basic natural resource, affecting ecosystems.

🔹 Main Ingredients:
1⃣ Minerals of different sizes.
2⃣ Air & water in open spaces.
3⃣ Organic material from decomposed plants & animals.

Soil Profile (Layers of Soil)

🌿 O Horizon (Surface Litter)

• Leaves & decomposing debris on top.

🌱 A Horizon (Topsoil)

• Organic matter, living organisms, inorganic materials.

• Thickest in grasslands.

⬇ E Horizon (Zone of Leaching)

• Dissolved & suspended materials move downward.

🟡 B Horizon (Subsoil)

• Yellowish due to iron, aluminum, humic compounds, and clay from A & E horizons.

⛰ C Horizon (Weathered Parent Material)

• Partially broken-down rock & minerals.

Factors Affecting Soil Formation

🌦 Climate

• Precipitation & temperature affect the weathering of parent material.

🦠 Living Organisms

• Bacteria (Rhizobium), fungi, insects, worms, snails help break down organic matter.

🪨 Parent Material

• The original rock & minerals that soil forms from.

• Can be native or transported by wind, water, glaciers.

🏔 Topography

• Land shape & elevation influence soil formation.

Soil Erosion

🌍 Definition:

• The movement of weathered rock/soil due to water, wind, or human activity.

⚠ Effects:

• Reduces water-holding capacity.

• Destroys soil profile.

• Increases soil compaction.

🚜 Poor Agricultural Practices That Cause Erosion:
❌ Improper plowing.
❌ Monoculture (planting only one crop).
❌ Overgrazing.
❌ Removing crop waste instead of returning it to the soil.

Landslides & Mudslides

🏔 Landslides

• Masses of rock, earth, or debris move down a slope.

• Can be triggered by heavy rain, droughts, earthquakes, volcanic eruptions.

🌊 Mudslides (Debris Flows)

• Fast-moving landslides that flow in channels.

• Begin on steep slopes and are worsened by wildfires or construction.

🌍 High-Risk Areas:
✅ Places with previous landslides.
✅ Locations with high surface runoff.
✅ Steep slopes or areas near rivers & canyons.

Rock Types

🔥 Igneous Rocks (Formed by cooling lava/magma)

• Intrusive: Cools slowly underground, large-grained.

• Extrusive: Cools quickly on surface, fine-grained.

• Weathering & water transport break them down.

🌋 Metamorphic Rocks (Formed by heat & pressure)

• Examples: Diamond, marble, slate, anthracite coal.

🪵 Sedimentary Rocks (Formed by layers of compacted materials)

• Only rock type that contains fossils.

Soil Components

🪨 Gravel

• Coarse particles made of rock fragments.

🏖 Sand

• Larger than silt, high permeability (water drains too quickly).

• Good for crops needing less water.

🌾 Loam

• Balanced mix of clay, sand, silt, & humus.

• Rich in nutrients & holds water without waterlogging.

💦 Silt

• Fine sediment between sand & clay in size.

• Easily transported by water.

🌑 Clay

• Very fine particles, compacts easily.

• Low permeability, leading to waterlogging.

🌱 Humus

• Dark organic material from decayed plants & animals.

• Improves soil structure, aeration, & pH stability.

• Mixed by earthworms.

Components of Soil Quality

💨 Aeration

• Refers to how well soil absorbs oxygen, water, & nutrients.

• Helps root growth & reduces soil compaction.

🧱 Soil Compaction

• Highly compacted soil has few large pores, reducing water infiltration & drainage.

🌾 Nutrient-Holding Capacity

• Ability to retain & provide nutrients for plants.

• Weathering releases nutrients, but leaching can reduce soil fertility.

• Key nutrients: Nitrogen (N), Phosphorus (P), Potassium (K).

💧 Permeability

• How well water & oxygen pass through soil.

• Low permeability can cause salinization.

🧪 pH Levels

• Acidic soil → caused by acid rain, pollution, or high rainfall.

• Alkaline soil → contains high potassium (K), calcium (Ca), magnesium (Mg), or sodium (Na).

🌿 Pore Size

• Determines how much water, air, & nutrients reach plant roots.

💧 Water-Holding Capacity

• Controlled by soil texture & organic matter.

• Fine soils hold more water, coarse soils drain faster.

🌍 Soil Texture

• Defined by particle size distribution.

• Affects moisture, nutrients, & oxygen retention.

🌱 Soil Food Web

• Community of organisms that live in soil.

• Affects nutrient cycling, plant health, & soil structure.

🌍 Greenhouse Effect & Early Life

CO2 (volcanoes) & CH4 (early microbes) → Strong greenhouse effect enabled life to develop.

💨 Great Oxidation Event (GOE) (2.5 BYA)

• Oxygen rise → killed most life on Earth.

• Methane (CH4) → oxidized into CO2, weakening the greenhouse effect, leading to cooling & ice ages.

• Higher O2 → biological diversification & chemical changes in atmosphere, oceans, and rocks.

Atmosphere’s Current Composition

🟡 Nitrogen (N2) - 78%

• Key nutrient for organisms (in amino acids & nucleic acids).

• Enters the atmosphere through denitrification & combustion.

🟢 Oxygen (O2) - 21%

• Vital for respiration & produced in photosynthesis.

• Became abundant 2.5 billion years ago.

💦 Water Vapor (H2O) - 0-4%

• Highest near the equator & oceans, lowest in polar & desert regions.

• Sources: evaporation, respiration, combustion, volcanoes, transpiration.

🌫 Carbon Dioxide (CO2) - <1%

• Produced by respiration, fossil fuel combustion, & decay.

• Absorbed in photosynthesis.

• Major greenhouse gas, lifespan ~100 years.

Atmosphere’s Structure

☁ Troposphere (0–10 km / 0–6 mi)

• 75% of atmosphere’s mass & almost all water vapor.

• Weather occurs here.

• Temperature & pressure decrease with height.

☀ Stratosphere (10–50 km / 6–30 mi)

• Ozone (O3) absorbs UV radiation.

• Temperature increases with altitude.

🌦 Weather

• Caused by heat energy transfer from unequal solar heating.

• Includes: Air pressure, temperature, humidity, precipitation, wind speed/direction, sunlight.

🌍 Climate

• Long-term weather patterns (months to millions of years).

• Controlled by latitude, altitude, ocean distance, albedo, & human activity.

🔥 Convection

• Main energy transfer process.

• Warm air rises, creating wind & pressure differences.

🌡 Heat Index (HI)

Feels like temperature with humidity factored in.

🌪 Air Mass

• Large body of air with similar temperature & moisture.

• Types: Equatorial, tropical, polar, Arctic, continental, maritime.

☀ Albedo

• Reflectivity of a surface.

• High albedo: Ice & snow.

• Low albedo: Oceans & dark land.

🌊 Oceans & Temperature Stability

• Water heats/cools slowly compared to land.

• Coastal areas have less extreme temperature changes than inland.

🌡 Fronts (Boundary Between Air Masses)

• Cold Front → Thunderstorms & strong winds.

• Warm Front → Gradual warming & light rain.

• Stationary Front → Lingering weather patterns.

🌿 Greenhouse Effect

• Keeps Earth warm, but excess traps heat → Global warming.

• Main greenhouse gases: H2O, CO2, CH4, N2O.

🏙 Human Activity & Climate

• Pollution increases rainfall in urban areas.

• Deforestation & urbanization impact climate.

🌍 Latitude & Sunlight

• Farther from equator = Less sunlight.

• Poles receive spread-out solar energy.

💨 Moisture Content of Air

Determines plant growth, biome type.

🌫 Pollution & Greenhouse Gases

Emitted from natural & human sources.

🌎 Earth’s Rotation & Temperature

Day/Night cycle affects daily temperature patterns.

🌋 Volcanoes & Climate

• Sulfur-rich eruptions → Cooling & stratospheric warming.

• Volcanic aerosols last 1–3 years & can damage ozone layer.

🌬 Land Breeze (Night)

• Land cools faster than the sea.

• Denser air over land moves to sea.

🌊 Sea Breeze (Day)

• Land heats up faster than the sea.

• Less dense air over land rises, and cooler sea air moves in.

🔄 Air Circulation

• Warm air rises due to Earth's rotation, revolution, and tilt.

• Cool air sinks, creating convection & winds.

🌪 Low-Pressure Systems

• Lower pressure at center.

• Air rises, forms clouds & precipitation.

🌞 High-Pressure Systems

• Higher pressure at center.

• Winds blow outward.

• Clockwise in Northern Hemisphere, counterclockwise in Southern Hemisphere.

• Associated with fair weather.

💨 Trade Winds

• Easterly surface winds in the tropics.

• Used by sailing ships for navigation.

🌬 Wind Speed & Direction

• Higher pressure difference = Higher wind speed.

• Easterly winds come from the east.

• Westerly winds come from the west.

🌍 Coriolis Effect

• Earth's rotation curves wind paths.

• Northern Hemisphere: Winds spiral clockwise out from high pressure & counterclockwise toward low pressure.

Hadley Air Circulation

🔥 Near the Equator

• Warm air rises, spreads north & south.

• High humidity, heavy rainfall → Rainforests.

🏜 Subtropical Regions

• Air cools, sinks, & becomes dry.

• Low humidity, little cloud formation → Deserts.

☀ Climate Characteristics

• Warm to hot summers, mild winters.

• Savanna climate has a dry season over two months long.

🌍 Ferrel Cells (30°–60° latitude)

• Mid-latitude climates → Defined seasons.

• Severe winters & cool summers due to cyclone patterns.

❄ Polar Cells (Above 60° latitude)

• Cold, dry air sinks → Polar deserts.

• Little precipitation because water is frozen.

🌪 Polar Vortex

• Low-pressure zone over poles with cold air.

• Strengthens in winter, weakens in summer.

• Antarctic vortex linked to ozone depletion.

🌊 Hurricanes (Cyclones/Typhoons)

• Over warm oceans where trade winds converge.

• Rotating thunderstorms absorb ocean moisture & heat.

• Eye → Low pressure, descending air.

• Storm surge → Sea level rise during storm.

🌪 Tornadoes

• Updrafts & downdrafts create a rotating mesocyclone.

• Warm air rises, cold air sinks, forming a funnel

🌧 Monsoons

• Seasonal winds changing direction.

• Winter: Blow from land to sea (dry season).

• Summer: Blow from sea to land (wet season).

💧 Watershed

• A land area that drains rainfall & snowmelt into a lake, ocean, or aquifer.

🌊 Mississippi River Watershed

• Largest watershed in the U.S.

• Drains over 1 million square miles.

🌱 Watershed Management

• Reduces pesticides & fertilizers from washing into waterbodies.

• Uses land, forest, and water resources responsibly.

• Protects plants, animals, and water quality.

☀ Angle of Sunlight

• Heat energy received depends on the sunlight's angle.

• Varies by location, time of day, & season.

• Tilt of Earth's axis causes seasonal changes.

• Lower angle = Weaker sunlight spread over a larger area.

🌍 Solar Intensity Factors

• Tilt of Earth’s axis (23.5°).

• Atmospheric conditions.

• Earth’s yearly orbit around the sun.

• Earth’s 24-hour rotation on its axis.

🌊 Bodies of Water and Climate

• Over 70% of Earth's surface is covered in water.

• Oceans & lakes store heat, adding moisture to air, driving air currents.

• Water stabilizes climate by absorbing heat in warm periods & releasing in cooler ones.

• Warm, moist ocean air drives precipitation patterns when carried over land.

🏞 Higher Elevations = Cooler Climates

• Elevation increases = cooler climates and longer cold seasons.

• Lower air pressure at higher elevations = cooler temperatures.

• High-altitude plains are deserts due to being downwind of mountains.

📏 Latitude and Tropics

• Latitude measures distance from the equator.

• Tropic of Cancer = northernmost latitude of overhead sun.

• Tropic of Capricorn = southernmost latitude of overhead sun.

🏔 Mountains and Air Flow

• Mountains act as barriers to air currents.

• Air cools & rains on windward side, creating a rain shadow effect on leeward side.

• Rain shadow affects plant & animal life on the leeward side.

🌊 La Nada (Normal Conditions)

• Easterly trade winds push water & air west.

• Western Pacific has warmer water (14°F) & higher ocean (24 inches).

• Upwelling brings nutrient-rich water to the surface.

🔥 El Niño (Warm Phase)

• Air pressure patterns reverse, weakening trade winds.

• Water piles up in the western Pacific, weakening upwelling.

• Warmer-than-average ocean temperatures occur off South America.

• Jet stream changes, increasing ocean warmth & affecting weather.

❄ La Niña (Cool Phase)

• Stronger trade winds push cooler water west, increasing upwelling.

• Cooler-than-normal ocean temperatures off South America.

• Wetter-than-normal in Pacific Northwest & drier in southern US.

• More hurricanes & cooler winters in southeast US.

🌎 Environmental Effects of ENSO Patterns

• Warmer/cooler ocean temperatures disrupt marine ecosystems.

• Decrease in upwelling = fish die-offs & negative effects on coral reefs.

• Changes in weather increase insect-borne diseases & migration patterns.

• Hurricanes & tornadoes become stronger & more frequent.

• Altered ocean currents & glacial melting with warmer oceans.

• Flooding and soil erosion with increased rainfall.