Study Notes on Earth Systems and Resources
Concepts in Science
Theory in Science: A well-substantiated explanation of a natural phenomenon based on a body of evidence.
Support for Theories: Backed by multiple lines of repeated evidence.
Evidence for Plate Tectonics
Proposed by Alfred Wegener.
Continental Drift Theory: Plates are said to “float” and move over the asthenosphere, which is part of the mantle that circulates due to convection currents.
Lithosphere: Earth’s solid outer layer divided into seven large pieces called tectonic plates.
Types of Lithospheric Crust
Continental Crust: Thicker and less dense.
Oceanic Crust: Thinner and more dense.
Most tectonic plates possess both types of crust.
Major Evidence for Plate Tectonics
Continents Fit Together:
The edges of continents resemble puzzle pieces, indicating they were once connected and have since drifted apart.
Fossils & Rock Records Match:
Identification of the same fossils and similar rock formations on widely separated continents suggests they were adjacent at one point in time.
Geologic Activity Patterns:
Patterns of geological activity such as volcanoes, earthquakes, trenches, and mountains generally form along plate boundaries, indicating interactions between plates as they move.
Types of Plate Interactions
Overview of Plate Interaction Types:
Transform Boundaries: Plates slide past each other. This is a conservative interaction, where the crust neither gets destroyed nor created. Example: Earthquakes at transform boundaries where two plates move against one another.
Convergent Boundaries: Plates come together, resulting in destructive interactions where crust can be lost. Examples include:
Ocean-Continent: Denser oceanic plate subducts under a continental plate, causing strong quakes (e.g., Andes mountains).
Ocean-Ocean: Older oceanic plate subducts beneath a younger oceanic plate, typically resulting in strong earthquakes and potential formation of tsunamis.
Continent-Continent: Two continental plates collide, resulting in thickening and shortening of the crust, leading to tall mountain formations without volcanic activity (e.g., Himalayas).
Divergent Boundaries: Plates pull apart, resulting in constructive interactions where new crust is created (e.g., rift valleys and mid-ocean ridges).
Volcanoes and Hotspots
Hotspots:
Are stationary plumes of hot mantle that penetrate moving tectonic plates. They can result in chains of volcanoes where the oldest volcano is farthest from the active one (e.g., Hawaii, Yellowstone).
Types of Faults
Transform Faults:
Involve sideways sliding of plates, resulting in frequent shallow earthquakes but typically lacking volcanic activity. Example: San Andreas Fault in California.
Natural Disasters Associated with Plate Tectonics
Earthquakes: Occur at all types of plate boundaries, resulting from the accumulation of stress in rocks that are suddenly released.
Tsunamis: Often occur at convergent boundaries, particularly where oceanic plates subduct, causing underwater megathrusts that lift the seafloor and displace vast quantities of water.
Soil and Its Importance
What is Soil?
Defined as a critical natural resource composed of mineral and organic matter that supports life.
Soil Formation:
Involves the breakdown of rocks into smaller pieces through a process called weathering, which can be further divided into:
Physical Weathering: Breaking down rocks through physical processes like wind.
Biological Weathering: Involves living organisms (like plants) breaking down rocks (e.g., root wedging).
Chemical Weathering: Decomposition of rocks through chemical reactions (e.g., oxidation).
Erosion: Removal and transport of weathered material, primarily by water or wind.
Deposition: The accumulation of sediments which can become the parent material for soil.
Importance of Soil
Organism Interactions: Soil supports a wide range of organisms that contribute to processes like decomposition and nutrient recycling.
Impact of Human Activity on Soil
Major human activities impacting soil health include:
Clear-Cutting and Deforestation: Leads to soil erosion and decreased fertility.
Intensive Agriculture: Practices like over-tilling and overgrazing deplete soil.
Desertification: Loss of vegetation causes barren lands due to erosion.
Properties Influencing Soil Formation
Original (Parent) Material: The bedrock influences mineral content and texture of the soil.
Time: Soil formation is a slow process; older soils have more developed profiles.
Climate: Temperature and precipitation also influence soil formation rates.
Topography: Shape and slope of land affect drainage and soil composition.
Living Organisms: Diverse organisms contribute to organic matter and nutrient cycling.
Soil Composition and Texture
Mineral Soil: Consists of inorganic solids from weathered parent rock, which includes different particle sizes influencing soil texture.
Soil Textures: Defined by percentages of sand, silt, and clay, with loam representing a balanced mixture.
Soil Porosity and Permeability: Refers to the spaces between particles that hold water, air, and organisms.
Water-Holding Capacity: The ability of soil to retain water when excess has drained.
Cation Exchange Capacity (CEC): The ability of soil to hold onto essential nutrient cations, critical for plant growth.
pH of Soil
pH Levels: A measurement of acidity. Higher hydrogen ions (H+) indicate more acidic soil, which can affect nutrient availability.
Soil Acidity: Impacts on nutrient leaching and overall fertility.
Human Impact: Chemical fertilizers and acid rain can increase soil acidity.
Solutions for Soil Acidity:
Lime the soil: Applying crushed limestone can help reduce soil acidity.
Soil Use Applications
Recommended soil types for various applications:
Sanitary Landfill: Clay is ideal due to low permeability, preventing leachate.
Athletic Turf: Sand's high permeability is beneficial.
Farming: Loam captures benefits from all textures for optimal growth.
Atmospheric Dynamics and Weather Patterns
Insulation and Solar Radiation
Insolation: Incoming solar radiation impacts climate and weather.
Varies by latitude, with higher intensity at the equator and lower toward the poles.
Greenhouse Effect
Greenhouse gases (GHGs) trap heat, which is critical for life on Earth. Human activities are increasing GHG levels, contributing to climate change.
Seasons and Earth’s Motion
The Earth’s axial tilt of 23.5° influences seasonal changes and day length.
Atmospheric Layers and Weather
Weather takes place primarily in the Troposphere (up to 12 km).
Other layers include the stratosphere (ozone layer), mesosphere, thermosphere, and exosphere.
Atmospheric Pressure
Defined as the weight of the air column above a given area; greater near the surface leading to weather phenomena.
Wind Formation
Wind arises from uneven heating of the earth’s surface, where warm air rises and cool air sinks.
Convection Currents: Generated by these temperature differences, impacting global weather patterns.
Ocean Dynamics and Climate Impact
Oceanic Contributions to Climate
Oceans influence atmospheric humidity and temperature, serving as a thermal reservoir that modifies weather patterns.
Upwellings
Processes along coastlines where warm surface water is displaced, which brings nutrient-rich water to the surface, supporting marine ecosystems and fisheries.
Ocean Gyres
Large, slow-moving current systems powered by wind and Earth’s rotation, shape climates by distributing heat and nutrients across oceans.
Climatic Events and Patterns
El Niño/Southern Oscillation (ENSO)
A recurring climate pattern characterized by significant changes in sea-surface temperatures and atmospheric conditions, influencing global weather patterns.
Three phases: ENSO-neutral, El Niño, and La Niña.
Watershed Characteristics
Watershed Definition: A land area draining to a single water point (stream, lake, or bay).
Characteristics influencing watershed effectiveness:
Area and Length: Case of influence on runoff volume.
Slope: Steeper slopes lead to faster runoff, potentially greater flood risks.
Soil Type: Influences permeability and runoff.
Vegetation: Roots and litter can enhance soil health and reduce runoff.
Divides: Physical barriers that separate different watershed areas.
Human Impacts on Watersheds
Common human impacts include urbanization, leading to increased runoff; agricultural runoff causing eutrophication; and dam construction affecting natural flow and habitats. Solutions may involve using permeable materials, increasing vegetation, and alternative energy strategies.