Chapter 1 - The Earth (copy)

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.