Environmental Unit 4

Unit 4 = Modules 19, 20, 21, 22, and 23

Module 19

Layers of Earth

1. Core: The innermost layer, divided into:

   1. Inner Core: Solid, primarily composed of iron and nickel.

   2. Outer Core: Liquid, primarily iron and nickel.

2. Mantle: Above the core, contains three sub-layers:

   1. Magma: Molten rock.

   2. Asthenosphere: Semi-fluid layer allowing tectonic plates to float.

   3. Solid Upper Mantle: Rigid layer, part of the lithosphere.

3. Crust: Earth’s outermost layer, forming the lithosphere along with the solid upper mantle.

Types of Plate Boundaries

1. Divergent Boundary:

   1. Plates move apart.

   2. Creates new oceanic crust through seafloor spreading.

   3. Example: Mid-Atlantic Ridge.

2. Convergent Boundary:

   1. Plates move toward each other.

   2. Subduction Zone: One plate sinks beneath the other, causing volcanic activity or forming island arcs.

   3. Example: Andes Mountains.

   4. Collision Zone: Continental plates collide, forming mountain ranges.

      1. Example: Himalayas

3. Transform Boundary:

   1. Plates slide past each other horizontally.

   2. Example: San Andreas Fault.

Evidence for Plate Tectonics

• Theory of Plate Tectonics: Proposed by Alfred Wegener in 1912, suggesting continents were once part of a supercontinent (Pangaea).

  • Evidence:

    •  Identical rock formations on different continents.

    •  Fossils of the same species found on separate landmasses (e.g., Mesosaurus in South America and Africa).

    • Continents fit together like a puzzle, indicating past connections.

Geologic Events and Effects

• Earthquakes:

  • Caused by sudden movements of Earth’s crust, often along transform boundaries.

  • Measured on the Richter Scale, which is logarithmic (each unit is 10x greater in magnitude).

• Volcanoes: Formed at subduction zones and hotspots.

  - Hot Spot: Region where magma rises through the mantle independently of tectonic boundaries (e.g., Hawaiian Islands).

- Tsunamis: Caused by underwater seismic activity, particularly from subduction zone earthquakes.

Global Tectonic Plates and Boundaries:

• Major Plates: Pacific Plate, North American Plate, Eurasian Plate, Indo-Australian Plate, and more.

• Boundary Indicators:

  • Spreading Zones: Plates move apart (divergent).

  • Subduction Zones: Plates converge, one slides beneath the other.

  • Collision Zones: Continental plates collide, forming mountains.

  • Movement Direction: Arrows indicate the direction of plate motion on maps.

Consequences of Plate Movement

• Impact on Biodiversity:

  • As continents drift, ecosystems and climates change, leading to species adaptation, speciation, or extinction.

• Human and Environmental Impact:

  • Earthquakes and volcanoes near population centers can lead to significant loss of life, infrastructure damage, and long-term environmental changes.

  • Ex: 2017 earthquake in Mexico City (7.1 magnitude) caused severe damage.

Main Ideas! 

• Layers of Earth: Solid core, liquid outer core, magma, asthenosphere, lithosphere.

• Plate Movement: Driven by circulating magma, causing divergent, convergent, and transform boundaries.

• Prediction of Geologic Events: Plate boundaries indicate likely locations of earthquakes, volcanoes, and other phenomena.

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Module 20

Types of Rocks and Their Formation

• Igneous Rocks: Form from magma.

  • Types: Basaltic (oceanic crust), Granitic (continental crust).

  • Examples: Granite, Pumice, Scoria, Obsidian.

• Sedimentary Rocks: Formed by compressed sediments; often fossil-rich.

  • Examples: Sandstone, Shale, Conglomerate, Limestone, Gypsum.

• Metamorphic Rocks: Created by heat and pressure.

  • Examples: Marble, Slate, Gneiss, Quartzite.

The Rock Cycle

• Processes:

  • Melting & Cooling: Forms igneous rocks.

  • Weathering & Erosion: Turns rocks into sediments.

  • Compaction & Cementation: Forms sedimentary rocks.

  • Heat & Pressure: Transforms rocks into metamorphic forms.

Soil Formation Factors

• Parent Material: Determines soil’s mineral content.

• Climate: Temperature and moisture influence formation rate.

• Topography: Slope affects erosion and soil depth.

• Organisms: Plants and animals add organic material, improve soil aeration.

• Time: Soil develops gradually; older soils are richer.

Soil Properties

• Physical Properties:

  • Texture: Mix of sand, silt, clay, affecting water retention.

  • Porosity: Space for air and water.

• Chemical Properties:

  • Cation Exchange Capacity (CEC): Soil’s nutrient-holding ability.

  • pH: Influences nutrient availability.

• Biological Properties:

  • Organisms like bacteria and earthworms aid nutrient cycling.

Weathering and Erosion

• Weathering:

  • Physical: Temperature changes, freeze-thaw cycles.

  • Chemical: Dissolution, oxidation.

  • Biological: Organisms produce acids, breaking down rocks.

• Erosion:

  • Natural (wind, water, ice, gravity) and human activities (deforestation) accelerate erosion.

  • Effects: Loss of fertile soil, sedimentation in waterways.

Soil Erosion Causes and Impacts

• Causes: Rainfall, wind, farming, logging.

• Impacts: Loss of productivity, water pollution, habitat disruption.

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Chapter 21

Characteristics of a Watershed:

• Definition: A watershed is an area of land where all the water drains into a particular body of water, such as a river, lake, or wetland.

• Characteristics:

  • Area and Length: The watershed size can vary significantly, from small areas to vast regions covering multiple states.

    • Example: The Mississippi River watershed spans nearly one-third of the United States, draining into the Gulf of Mexico.

  • Slope: Determines the speed and direction of water flow.

    • Steeper slopes result in faster water movement, which can increase erosion.

  • Soil Type: Influences water absorption and flow.

    • Sandy soils allow water to infiltrate quickly, while clay soils retain water.

  • Vegetation Type: Plants stabilize soil, reduce erosion, and improve water quality.

    • Forested areas with dense vegetation can help slow water flow and increase absorption

Human Impacts on Watersheds:

• Water Flow Alteration: Construction, urbanization, and deforestation can change natural water pathways.

  • Example: Roads and buildings prevent water infiltration, leading to increased surface runoff and potential flooding.

• Excess Nutrient Runoff: Agriculture and urban runoff introduce nutrients and pollutants into waterways.

  • Effects: Excess nutrients can cause algal blooms, reducing oxygen levels and harming aquatic life.

• Water Pollution: Chemicals from industrial and agricultural activities can contaminate watersheds.

  • Pollutants like pesticides, heavy metals, and plastics degrade water quality and harm ecosystems.

Watershed Examples:

• Hubbard Brook Watershed (New Hampshire):

  • Known for long-term ecological studies on the effects of deforestation on water cycles.

  • Findings show that deforestation leads to increased runoff, nutrient loss, and changes in water quality.

• Chesapeake Bay Watershed:

  • Largest watershed on the U.S. East Coast, covering six states.

  • Subject to nutrient pollution from agriculture, leading to hypoxic (low oxygen) zones harmful to marine life.

  • Conservation efforts focus on reducing nutrient inputs and improving water quality.

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Chapter 22

Composition and Structure of Earth’s Atmosphere

• Major Gasses:

  • Nitrogen (78%) and Oxygen (21%) dominate Earth's atmosphere.

  • Other gasses like carbon dioxide and argon play minor roles but significantly influence the greenhouse effect.

• Atmospheric Layers:

  • Troposphere: Closest to Earth; weather occurs here; temperature decreases with altitude.

  • Stratosphere: Contains the ozone layer, absorbing UV radiation; temperature increases with altitude.

  • Mesosphere: Coldest layer; meteors burn up here.

  • Thermosphere: Contains the auroras; temperature increases with altitude.

  • Exosphere: Outermost layer, gradually transitions into space.

Properties of Air and Atmospheric Circulation

• Air Properties:

  • Density: Warm air is less dense and rises; cool air is denser and sinks.

  • Water Vapor Capacity: Warm air holds more moisture; cooling leads to condensation and precipitation.

• Adiabatic Processes:

  • Adiabatic Cooling: Air rises, pressure decreases, temperature drops.

  • Adiabatic Heating: Air sinks, pressure increases, temperature rises.

  • Latent Heat Release: Energy released during condensation, warming surrounding air.

• Convection Currents:

  • Hadley Cells: Located between the equator and 30° latitude, responsible for tropical and desert climates.

  • Ferrel Cells: Between 30° and 60° latitude; bridge polar and Hadley cells.

  • Polar Cells: Between 60° latitude and the poles; cold air sinks at the poles.

Solar Radiation and Seasons

• Earth’s Tilt and Seasons:

  • Earth’s 23.5° tilt causes seasonal variations in sunlight distribution.

  • Equinoxes (March & September): Day and night are approximately equal worldwide.

  • Solstices (June & December): Longest and shortest days of the year. 

• Albedo:

  • Reflectivity of surfaces; higher albedo (like snow) reflects more sunlight, while lower albedo (like forests) absorbs more.

Global Wind Patterns and the Coriolis Effect

• Global Wind Patterns:

  • Trade Winds: East-to-west winds near the equator due to Hadley cell activity.

  • Westerlies: West-to-east winds in mid-latitudes due to Ferrel cell activity.

  • Polar Easterlies: East-to-west winds near the poles.

Coriolis Effect:

•  Earth’s rotation causes winds to deflect, creating curved paths.

  • Northern Hemisphere: Winds deflect to the right.

  • Southern Hemisphere: Winds deflect to the left.

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