Chapter 4 exam

Unit 4: Earth’s Systems and Resources

Lesson 1: Plate Tectonics

• The Earth’s Layers

  • Lithosphere: The hard crust of the Earth that includes the upper mantle and the crust, providing a rigid layer that supports tectonic activity.

  • Asthenosphere: The semi-fluid layer beneath the lithosphere that allows for the movement of tectonic plates.

  • Mesosphere: The strong, lower part of the mantle located beneath the asthenosphere, characterized by increased pressure and temperature, contributing to the overall dynamics of plate movement.

  • Outer Core: The liquid layer composed primarily of iron and nickel that generates the Earth's magnetic field through its flow, situated beneath the mesosphere.

  • Inner Core: The solid innermost layer of the Earth, composed mainly of iron and nickel, with extremely high temperatures and pressures, and believed to play a crucial role in the generation of the Earth's magnetic field.

Tectonic Plate Theory

• Historic Proposal: First proposed by Alfred Wegener in 1915 as the pangea of continental drift, suggesting that continents were once connected and have since moved apart.

• Plate Boundaries: The edges where two tectonic plates meet, classified into three types: divergent, convergent, and transform.

• Structure: The lithosphere is broken into 15 tectonic plates that float on the denser, molten asthenosphere.

Evidence for Tectonic Plate Theory

• 1. Continental Fit: Continents resemble puzzle pieces, supporting the theory of Pangea.

• 2. Fossil and Rock Distribution: Similar fossils and rocks found on distant continents, indicating they were once connected.

• 3. Geological Activity: Earthquakes, tsunamis, volcanoes, and mountain formations occur at plate boundaries.

Types of Crust and Hotspots

• Hotspots: Locations of magma plumes in the lithosphere that can create islands and volcanoes.

  • Example: Hawaiian Islands (oceanic hotspot) and Yellowstone National Park (continental hotspot).

Types of Plate Boundaries

1. Convergent Plate Boundary

• Oceanic + Oceanic: Subduction leads to trenches and volcanic activity (e.g., Mariana Trench).

• Oceanic + Continental: Oceanic subduction results in volcanic mountains (e.g., the Pacific Ring of Fire).

• Continental + Continental: Forms mountain ranges and causes earthquakes (e.g., Himalayas).

2. Divergent Plate Boundary

• Causes upwelling of magma and the formation of new crust.

• Oceanic Divergence: Sea-floor spreading creates undersea mountains (e.g., Mid-Atlantic Ridge).

• Continental Divergence: Forms rift valleys (e.g., African Rift Valley).

3. Transform Boundary

• Movement: Plates slide past each other, causing friction and tension.

• Result: Earthquakes occur when accumulated stress is released (e.g., San Andreas Fault).

Earthquakes

• Mechanism: Fault lines lock up, building stress until released, causing ground tremors.

• Measurement: Recorded by seismographs, rated on the Richter scale.

Tsunamis

• Cause: Sudden underwater fault slips release energy, forming large ocean waves.

• Behavior: Waves increase in size as they reach shallow waters.

Volcanoes

• Formation: Magma from the asthenosphere reaches the surface through ruptures in the lithosphere.

• Location: Primarily found at subduction zones, divergent boundaries, and hotspots.

  • Eruption products: Ejecta (ash, rocks), magma (cools to form igneous rock), gases (mostly water vapor, CO2, sulfur dioxide).

• Aftermath: Ash can inhibit sunlight for photosynthesis; sulfur dioxide can lead to global cooling through the formation of aerosols.

Lesson 2: Soil Formation & Properties

• What is Soil?

  • A mix of rock particles, decaying organic matter (humus), air, water, and living organisms.

• Importance: Healthy soil is critical for biodiversity and food security.

• Aeration

  • Definition: The process of introducing air into a substance, particularly soil.

  • Importance in Soil:

    • Allows for the exchange of gases between the soil and atmosphere, essential for plant root health and soil organisms.

    • Facilitates oxygen supply to roots and helps remove excess carbon dioxide.

  • Methods of Aeration:

    • Mechanical aeration, manual cultivation, and maintaining soil structure through appropriate farming practices.

How Does Soil Form?

• Processes: Formation involves the interaction of decaying organic matter and weathered parent bedrock over time.

• Horizons: Distinct layers develop, influenced by both biotic and abiotic factors in the environment.

• Soil Horizons:

  • O Horizon: Organic matter, decomposed material.

  • A Horizon (Topsoil): Mixture of organic and mineral material, where most biological activity occurs.

  • E Horizon: Leached minerals and nutrients, common in acidic soils.

  • B Horizon (Subsoil): Accumulation of minerals and organic matter from above.

  • C Horizon: Weathered parent material, could also include bedrock.

  • R Horizon: Unweathered bedrock.

• Soil Formation: Involves weathering processes (chemical, physical, biological) and time.

Parent Material (rock)

• Weathering types:

  • Chemical: Alterations due to acids.

  • Physical: Weathering due to wind and water.

  • Biological: Breakdown via lichens and plant roots.

• Erosion: Movement away from the rock location by wind, water, landslides, etc.

Properties Affecting Soil

1. Parent Material: Determines chemical properties and mineral content (e.g., quartz is nutrient poor).

2. Climate: Temperature and precipitation affect biomes and influence soil weathering and nutrient leaching.

• Examples of effects: Rainforests have rapid weathering but poor soil nutrients.

3. Topography: Steeper landscapes lead to higher erosion and less saturated soil during precipitation.

4. Organisms: Contribute to soil health through decomposition, aeration, and organic contributions.

5. Time: Soil evolves from young (without horizons) to mature (rich in nutrients) over time.

Soil Horizons and Types

• Soil texture: Classified as sand, silt, clay with loam being a mix of all three, ideal for agriculture.

• Physical properties: Influenced by porosity, permeability, and texture related to coarse sand, silt, and clay.

• Chemical properties: Cation Exchange Capacity (CEC) affects nutrient retention—clay has high CEC.

Lesson 3: Human Use & Impact on Soil

• Soil type applications: Different soils used strategically based on their properties (e.g., clay for lining landfills).

• Fertile soil: Ideal soils have loam texture, high nutrients, and naturally take hundreds to thousands of years to form.

Human Impacts on Soil

1. Cattle Ranching: Erodes soil due to animal impact and prevents plant regeneration.

2. Industrialized Agriculture: Involves high input methods leading to compacted soil and erosion—techniques include heavy machinery and tilling.

3. Deforestation/Construction/Mining: Removal of vegetation leads to soil erosion and nutrient loss.

Soil Erosion

• Definition: The removal of the top layer of soil due to various forces such as water, wind, and human activities.

• Causes of Soil Erosion:

  • Water Erosion: Rainfall and surface runoff can wash away soil, particularly in steep areas without vegetation.

  • Wind Erosion: Strong winds can pick up loose, dry, and bare soil particles, especially in arid regions.

  • Human Activities: Deforestation, overgrazing, and industrialized agriculture can remove protective vegetation, making soil more vulnerable to erosion.

• Impacts of Soil Erosion:

  • Decreases soil fertility, leading to lower agricultural yields.

  • Can lead to sedimentation in rivers and streams, negatively affecting water quality and aquatic life.

  • Results in loss of arable land and contributes to food insecurity.

• Prevention and Solutions:

  • Maintaining Vegetation: Keeping plants and cover crops can help protect soil from rainfall and wind.

  • Contouring and Terracing: Altering land contours can reduce runoff and erosion in hilly areas.

  • No-Till Farming: Reduces soil disturbance, helping to maintain soil structure and reduce erosion.

  • Agroforestry Practices: Integrating trees with crops can improve soil health and reduce erosion.

Case Study: The Dust Bowl

• Description: Major ecological disaster in the 1930s from poor agricultural practices, drought, and winds—resulting in massive dust storms and homelessness.

Solutions to Soil Erosion

• Key Approach: Maintain year-round vegetation.

• Techniques in Ranching: Such as nomadic grazing to alleviate overgrazing issues.

• Techniques in Farming:

  • No-till farming to prevent erosion and maintain soil structure.

  • Crop rotation to improve soil health and reduce reliance on fertilizers.

  • Agroforestry practices to support biodiversity and reduce erosion.

Lesson 5 & 6: Earth’s Atmosphere, Climate, and Weather

• Atmospheric Layers: Transitioning from ground to space involves 5 distinct layers, each with unique temperature profiles.

• Weather vs. Climate: Weather refers to short-term atmospheric conditions, while climate is the long-term pattern of weather.

• Key Factors Influencing Climate: Earth's tilt, solar insolation, convection currents, the Coriolis effect, and oceanic influences.

• El Niño and La Niña:

  • El Niño: Warm phase of ENSO, can cause heavy rainfall and flooding.

  • La Niña: Cool phase of ENSO, typically leads to drier conditions in some regions.

  • Impacts on Weather Patterns: Both El Niño and La Niña significantly disrupt normal weather patterns, affecting agriculture, fisheries, and water resources across the globe.

Watersheds

• Definition: Land area directing snowmelt and rainfall to a singular point (ocean/lake).

• Human Impacts: Activities like logging and urban development alter water flow and contribute to pollution.

• Solutions: Develop strategies for restoring watersheds and managing runoff effectively to promote ecosystem health.