Unit 4 Exam

4.1 Plate Tectonics

Overview

Plate tectonics explains the structure and motion of Earth's outer shell, resulting in various geological features and activities such as mountains, earthquakes, and volcanic eruptions.

Key Concepts

• Location of Mountains and Volcanoes: Mountains and volcanoes are primarily located at or near tectonic plate boundaries due to the interactions between these plates.

Types of Plate Boundaries

1. Convergent Boundaries: "Collide to Create"

   • Formation: Plates crash into each other, forming mountains and volcanoes.

   • Example: Himalayas and Andes.

2. Divergent Boundaries: "Divide to Thrive"

   • Formation: Plates pull apart, resulting in rift valleys and new oceanic crust.

   • Example: Mid-Atlantic Ridge.

3. Transform Boundaries: "Slide to Decide"

   • Formation: Plates slide past each other, mostly causing earthquakes.

   • Example: San Andreas Fault.

Important Features

• Subduction Zones: Areas where one tectonic plate slides beneath another, typically found at convergent boundaries.

• Rift Valleys: Lowland regions that form when a tectonic plate is pulled apart, commonly found at divergent boundaries (e.g., East African Rift).

• Hot Spots: Locations where magma from the mantle reaches the surface, creating volcanoes even in the middle of tectonic plates. The Hawaiian Islands are an example.

The Ring of Fire

• Location: A horseshoe-shaped zone in the Pacific Ocean basin, known for its high volcanic and earthquake activity.

• Significance: Hosts about 75% of the world’s active volcanoes and is a result of tectonic plate interactions.

Identifying Features

• Mid-Atlantic Ridge: An underwater mountain range formed by divergent tectonic activity.

• San Andreas Fault: A transform fault that forms the boundary between the Pacific Plate and the North American Plate.

• Hawaii: Significant as a hot spot that has resulted in a chain of islands formed by volcanic activity.

Review Questions

1. What physical features are associated with each type of plate boundary?

2. Describe a subduction zone and where it forms.

3. Explain what rift valleys are and where they occur.

4. Discuss the importance of the Ring of Fire and its location.

5. Identify and describe the significance of the Mid-Atlantic Ridge and the San Andreas Fault.

4.2 Soil Formation and Erosion

Soil Horizons

• Layers of Soil:

  • O Horizon: Organic matter, decomposed leaves and living organisms.

  • A Horizon: Topsoil, rich in nutrients and organic matter, crucial for plant growth.

  • E Horizon: Eluviation layer, mineral and nutrient leaching occurs here, often lighter in color.

  • B Horizon: Subsoil, accumulates minerals leached from upper layers, often denser and less fertile.

  • C Horizon: Parent material, composed of weathered rock and minerals, less affected by soil-forming processes.

  • R Horizon: Bedrock, solid rock layer beneath the soil.

Size of Soil Particles

• Types:

  • Sand: Large particles, well-drained, low nutrient retention.

  • Silt: Medium-sized particles, holds moisture better than sand.

  • Clay: Smallest particles, retains water and nutrients well, but drains poorly.

Nutrient Levels

• The availability of nutrients varies across soil profiles, with the top layers (O and A) typically having the highest nutrient levels, essential for plant growth.

Significance of Darker Colored Soils

• Darker soils are typically richer in organic material (humus) and carbon, indicating higher fertility and moisture retention capacity.

Humus

• Definition: Decomposed organic matter that enriches the soil and improves its structure.

• Importance: Essential for soil health, enhances water retention, nutrient content, and microbial activity.

Sedimentation

• Definition: The process of deposition of soil particles carried by water or wind.

• Leading Causes: Erosion, water flow, human activities (deforestation, agriculture).

Soil Erosion

• Causes: Natural factors (wind, water, gravity), human activities (agriculture, construction).

Effects of Forests on Soil Erosion

• Positive Effects: Forests reduce soil erosion by stabilizing soil with root systems, improving water infiltration.

• Negative Effects: Overharvesting can lead to increased erosion rates.

Soil Triangle

• Understand how to read the soil triangle to determine soil texture based on the relative proportions of sand, silt, and clay.

Water Filtration

• Soil acts as a natural filter, cleaning water as it percolates through various layers, trapping contaminants and providing clean water.

Landfill Construction

• Reason for Clay Base: Landfills should be built on clay due to its low permeability, which helps contain leachate and prevents groundwater contamination.

4.3 Soil Composition and Properties

Water Holding Capacity: The ability of soil to retain moisture for use by plants.

• Greatest capacity: Clay soils (due to smaller particles and tighter spaces).

• Least capacity: Sand soils (larger particles lead to less water retention).

Permeability: The ease with which water passes through soil.

• Relationship with Porosity: Higher porosity generally increases permeability; however, it is also affected by the arrangement of particles.

Porosity: The volume of pore space in soil compared to the total volume of soil.

• Changes with Texture:

  • Sand: High porosity (but low water retention).

  • Silt: Moderate porosity.

  • Clay: High porosity (with high water retention).

Loam: A balanced mixture of sand, silt, and clay, making it the ideal soil for agriculture due to its good drainage, water retention, and nutrient-holding capacity.

• Why it’s the "GOLDEN" soil: Supports optimal plant growth.

pH Scale: Measures the acidity/alkalinity of soil, impacting nutrient availability and crop growth. Aim for neutral pH (6-7) for most crops.

Nutrient Importance:

• Nitrogen: Essential for plant growth and leaf development.

• Phosphorus: Crucial for root development and flowering.

• Potassium: Helps with overall plant health and disease resistance; aids in water regulation.

4.4 Earth’s Atmosphere

Layers of the Atmosphere (from Earth’s Surface to Outer Space)

1. Troposphere - tropical/weather

2. Stratosphere - ozone layer

3. Mesosphere - meteors burn up

4. Thermosphere - very hot, northern lights

5. Exosphere - satellites

   (Mnemonic: The Snail Missed The Exit)

Temperature Trends

• Temperature generally decreases with altitude in the Troposphere and Mesosphere, while it increases in the Stratosphere and Thermosphere.

Ozone Layer

• Location: Within the Stratosphere.

• Functions:

  • Protects against harmful UV radiation.

• Importance: Vital for protecting life on Earth.

• Deterioration: Ozone depletion due to chemicals like CFCs.

Types of UV Radiation

• UVA: Ageing - Longer wavelengths, can age skin.

• UVB: Burn - Shorter wavelengths, can cause sunburns.

• UVC: Critical - Most harmful, blocked by the atmosphere.

Greenhouse Gases

• Types:

  • Carbon Dioxide (CO2) - Carbon - Fossil fuels, deforestation.

  • Methane (CH4) - Manure - Agriculture, landfills.

  • Nitrous Oxide (N2O) - Nitrogen - Fertilizers, vehicle emissions.

  • Water Vapor - Vapor - Natural sources, human activities.

Auroras

• Found in the Thermosphere near the poles, resulting from solar wind interactions with Earth's magnetic field.

Atmospheric Composition

• Majority of oxygen concentrated in the Troposphere.

Density of Layers

• Most Dense Layer: Troposphere.

4.5 Global Wind Patterns

Key Concepts

• Global Wind Patterns: Understand the primary wind patterns of Earth:

  • Easterlies: Winds blowing from east to west.

    • Trade Winds: Consistent winds that flow from east to west in the tropics.

  • Westerlies: Winds blowing from west to east.

Atmospheric Circulation Cells

• Hadley Cells: Located between the equator and 30° latitude; warm, rising air creates low-pressure at the equator.

• Ferrel Cells: Found between 30° to 60° latitude; influenced by the Hadley and Polar cells, typically characterized by westerlies.

• Polar Cells: Located near the poles, where cold air descends creating high pressure.

Solar Radiation

• Variation by Latitude: Solar radiation intensity varies with latitude; equatorial regions receive more direct sunlight while polar areas receive less.

• Seasonal Changes: Changes in solar radiation throughout the year impact weather patterns and climate.

Coriolis Effect

• Definition: The Coriolis effect refers to the apparent curvature of the path of a moving object due to the Earth's rotation.

• Air Mass Deflection: This effect causes winds to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, impacting global wind patterns and ocean currents.

4.6 Watersheds

Watersheds

Definition

A watershed is a piece of land where water flows to a central location.

Flood Plains

• Characteristics: Fertile and flat areas that are close to transportation routes.

Dams

• Function: Prevent water flow.

• Benefits:

  • Provide recreation areas

  • Serve as sources of drinking water

  • Offer inexpensive electricity.

Pollution

• Types of Pollution: Understand the difference between point source and non-point source pollution in relation to watersheds.

Water Flow

• Key Concepts:

  • Upstream: The direction from which water is coming.

  • Downstream: The direction in which water flows.

     

4.7 Earth's Seasons

Understanding Seasons

Key Concepts

• Reason for Seasons: Seasons occur due to Earth's axial tilt (approximately 23.5 degrees) and its orbit around the Sun.

• Solar Radiation Variations: Changes in solar radiation influence temperatures and weather patterns based on Earth's tilt and position.

Significant Dates

• December 21: Winter Solstice in the Northern Hemisphere (shortest day of the year).

• June 20: Summer Solstice in the Northern Hemisphere (longest day of the year).

Polar Night and Polar Day

• Polar Night: Occurs in polar regions during winter when the sun does not rise for an extended period.

• Polar Day: Occurs in polar regions during summer when the sun remains above the horizon for an extended time.

Temperature Variations

• Equator: Remains hot throughout the year due to direct sunlight.

• Polar Regions: Remain cold due to the angle of sunlight received, leading to less intense solar radiation.

4.8 Earth's Climate

Rain Shadow Effect

• Definition: A phenomenon where one side of a mountain range experiences significant rainfall while the opposite side remains dry.

• Causes: Due to elevation and prevailing winds.

Precipitation and Altitude

• Summary: As altitude increases, precipitation patterns change; higher elevations tend to receive more precipitation due to orographic lift.

Albedo Effect

• Definition: A measure of how much light that hits a surface is reflected without being absorbed.

• Importance:

  • Light colors reflect sunlight.

  • Dark colors absorb sunlight.

  • Contributes to warming when polar ice caps melt, reducing the Earth's albedo and leading to increased temperatures.

4.9 El Nino and La Nina

Understanding ENSO (El Niño-Southern Oscillation)

ENSO is a climate pattern that shows how ocean temperatures and weather conditions change in the Pacific Ocean near the equator.

Key Concepts

• Sea Surface Temperature Changes: The ocean has areas of warm and cold water that change over time.

• High Pressure/Low Pressure: Air pressure changes influence weather patterns.

• Precipitation: The amount of rain is affected by air temperature and ocean conditions.

• Ocean Upwelling: Deep, cold ocean water rises to the surface, bringing nutrients that help marine life grow.

Differences Between El Niño and La Niña

• Speed of Trade Winds:

  • El Niño: Trade winds become weaker.

  • La Niña: Trade winds are stronger.

• Warm Water Shift:

  • El Niño: Warm water shifts towards the Americas.

  • La Niña: Warm water is pushed towards Asia.

• Climate Patterns:

  • El Niño: More rain in the Americas; dry weather in Australia.

  • La Niña: More rain in Australia; dry weather in the Americas.

Connection to Fishing

• El Niño: Reduces nutrient-rich water, leading to fewer fish along South America’s coast.

• La Niña: Increases nutrient-rich water, supporting more fish.

Upwelling Explained

• What is Upwelling?: It's when deep, nutrient-rich water moves up to the surface, helping marine ecosystems.

• Differences in Upwelling Effect:

  • El Niño: Less upwelling due to warmer surface temperatures.

  • La Niña: More upwelling because of cooler water and stronger winds.