Chapter 1 - The Earth

Geologic Time Scale

  • Earth’s past eras have been separated by major events:   * Key Principles of the geologic time scale:     * Strata (Rock layers) are laid down in succession representing a slice of time.     * Principle of Superposition: Any given layer is older than the layers above them and younger than the layers below them.
  • Complications to the Geologic Time Scale   * Layers are eroded, distorted, tilted, or inverted after deposition   * Layers in different areas laid down at the same time can look different   * A layer from one area only tells a part of Earth’s history

Earth’s Structure

  • Earth can be divided into 3 sections:   * The Biosphere     * Includes all forms of life both on land and sea.   * The Hydrosphere     * Includes all forms of water.   * The Internal Structure     * Divided into the crust, mantle, and core.
  • The Layers of the Earth   * The Crust     * Makes up 0.5% of Earth’s total mass.     * Subdivided into the continental crust and the oceanic crust.     * The crust is rocky and brittle.   * Continental Crust     * Extends down 20-30 miles.     * Continental Crust is stratified (layered) and becomes more dense with depth.     * Largely composed of sedimentary, volcanic, and granite-like rocks     * Older areas contain metamorphic rocks.   * Oceanic Crust     * Relatively thin part of the crust.     * Consists of Basaltic Rock overlain with sediments.     * Younger and contains different chemical composition   * Mantle     * Most of Earth’s mass is in the mantle.     * Composed of iron, magnesium, aluminum, and silicon-oxygen compounds.     * Most of the mantle is solid.     * The asthenosphere (upper third) is more plastic-like.   * Lithosphere     * It is broken up into huge sections called tectonic plates.     * The movement of the lithosphere causes a lot of Earth’s events.   * Core     * Mostly composed of iron.     * Outer core is molten.     * Inner core is solid.

Plate Tectonics

  • Plate Tectonic Theory   * Earth’s lithosphere is divided into huge sections called tectonic plates that drift over the mantle   * Arose from the concept of seafloor spreading and continental drift.
  • Continental Drift Theory   * Alfred Wegener proposed that all continents used to be one single landmass.   * Wegener believed that the supercontinent started breaking apart 200 million years ago.
  • Seafloor Spreading Theory   * Alternating magnetic patterns were found in rocks found on the seafloor.   * Similar patterns were found on the other sides of mid-ocean ridges and in the center of ridges.   * Suggested that new crust was made at volcanic rifts zones.   * Subduction Zones are where two tectonic plates meet together and one plate slides under the other and moves toward the mantle.
  • Types of Boundaries - Convergent, Divergent, Transform   * Transform Boundaries     * Occur when plates slide past each other.     * They frequently cause earthquakes because of friction and the stress buildup between them.   * Divergent Boundaries     * Occur when two plates slide apart from each other.     * The space created between the two plates will fill up with molten magma.     * Can create massive fault zones in the oceanic ridge system and are areas of frequent oceanic earthquakes.   * Convergent Boundaries     * Occurs when two plates slide together     * Commonly forms subduction zones or an orogenic belt.     * When a dense oceanic plate subduct a less-dense continental plate, an oceanic trench can form, and a mountain range on the continental side.     * When two oceanic plates converge, they create an island arc - a chain of volcanic islands rising from the seafloor.     * When two continental plates collide, mountain ranges are created because of the crust being compressed and pushed upward.

Earthquakes

  • Earthquakes   * They occur during abrupt movement on a fault, tectonic plate boundaries, or along mid-ocean ridges.   * A massive store of energy is released in a short period of time when plates slide past each other.
  • Focus: The place where all the energy is released.
  • Richter Scale   * The strength of an earthquake is measured using the Richter scale.   * It compares the amplitudes of waves instead of the strength of the earthquakes.
  • Body and Surface Waves   * Body Waves     * Body waves travel through Earth’s interior. There are two types - P waves and S waves.       * P waves travel throughout Earth and are caused by the expansion and contraction of bedrock.       * S waves are produced when a material moves either vertically or horizontally.     * Surface waves produce rolling and/or swaying motions. They are slower than P and S waves. These waves cause damage and ground motion.

Tsunamis

  • Tsunamis   * Series of waves created when a body of water is rapidly displaced, usually from an earthquake.   * They can be generated when plate boundaries move and displace the water vertically.

Volcanoes

  • Volcanoes   * Divided into 4 categories - active, inactive, dormant, extinct.   * Active volcanoes produce magma at the surface.   * Majority of active volcanoes produce magma at subduction zones or mid-ocean ridges.   * Active volcanoes produce ejecta (lava rock/ash), molten lava, and gases such as sulfur dioxide.
  • Volcanic Eruptions   * Eruptions occur whenever pressure inside a magma chamber forces molten magma up to the top of the volcano to erupt.   * Benefits of volcanic eruptions include producing land, and increased soil production from the erosion of lava rock.

Solar Intensity, Seasons, and Longitude/Latitude

  • Solar Intensity   * Factors that affect the amount of solar energy at the surface of the Earth include Earth’s rotation, the tilt of Earth’s axis, and atmospheric conditions.
  • Seasons   * Seasons are not caused by the distance away from the sun, but from the angle of sunlight hitting Earth.
  • Latitude/Longitude   * Longitude is East/West positions on Earth. 0 degrees longitude begins in the Prime Meridian. The degrees continue 180 degrees east/west to meet at the International Date Line.   * Latitude is North/South positions. 0 degrees is the equator. 90 degrees north is the North Pole. 90 degrees south is the South Pole.

Soil

  • Soil   * Soil is the thin layer on the top of Earth’s surface. It affects every part of the ecosystem.   * Soil is composed of minerals of different sizes, organic materials from the remains of dead organisms and plants, and open space that can be filled with air and water.
  • Soils develop due to different factors   * Parent Material - Rock and material from where the soil derives   * Climate - Precipitation and Temperature   * Living Organisms - bacteria, fungi, worms, snails, insects that help decompose   * Topography - the characteristics of where the soil is located
  • Humus   * Dark material formed when plant and animal matter decays.   * Earthworms often help mix humus with minerals in the soil.   * This allows air and water to go through the soil
  • Soil Quality   * Aeration - How well the soil can absorb nutrients, water, and oxygen.   * Degree of soil compaction - How compact the soil is.   * Nutrient - Holding Capacity - How well the soil can contain and hold nutrients   * Permeability - The capacity that can allow water and oxygen to pass through it   * pH - How acidic or basic a soil is.   * Pore Size - The space between soil particles.   * Size of soil particle - Determines the amount of water and nutrients that the soil can hold   * Water - Holding Capacity - Controlled primarily by the soil texture.
  • Soil Food Web   * Community of organisms living their whole lives or part of their lives in the soil. Describes the complexity of the living system in the soil.
  • Soil Erosion   * The movement of weathered rock or soil components from one area to the other.   * Caused by human activities, flowing water, wind.   * Causes damage to the soil, agriculture, canals, and dams.
  • Landslides and Mudslides   * Occurs when masses of rock, earth, or debris moves down a slope.   * Mudslides tend to flow in channels.   * Landslides are caused by disturbances in the natural stability of a slope.   * Mudslides occur when water rapidly collects in the ground and causes in a surge of water-filled rocks.

The Rock Cycle

  • Igneous Rocks   * Formed by cooling   * Broken down by weathering and water transport.   * Most soil comes from Igneous Rocks
  • Metamorphic Rocks   * Formed by intense heat and pressure.   * High Quartz content forms sandy soil.   * Slate forms silty soil.   * Marble forms limestone clay.
  • Sedimentary Rocks   * Formed by piling and cementing various materials over time. Fossils form in sedimentary rocks.

\