THE EARTH & SOIL - 2019

Geology: Study of Earth's dynamic processes on the surface and in the interior.
Formation of Earth's Interior:
- Comprised of three major layers:
  - Core:
    - Innermost layer, extremely hot.
    - Solid inner core surrounded by liquid outer core.
    - Composed mainly of iron and nickel.
  - Mantle:
    - Mostly rock, some molten near the surface (asthenosphere).
  - Crust:
    - Outermost and thinnest layer.
    - Divided into oceanic and continental crust.

Tectonic Plates:
- Crust broken into huge rock plates, consisting of crust and upper mantle.
- Collectively called lithosphere.
- Floating on the asthenosphere due to convection currents in the mantle.
- Maps can determine locations of volcanoes, earthquakes, island arcs, etc.

Convergent Boundary:
- Plates pushed together.
- Types of outcomes depend on plate types involved:
  - Oceanic and Continental Plate Collision:
    - Denser oceanic plate subducts into the mantle, forming a trench (e.g. Marianas Trench).
  - Continental Plate Collision:
    - Forms mountains through uplifting (e.g. Himalayan Mountains).

Divergent Boundary:
- Plates moving apart.
- Results include seafloor spreading, rift valleys, earthquakes, and volcanoes.
  - Oceanic Plates create oceanic ridges (e.g. Mid-Atlantic Ridge).

Transform Boundary:
- Plates slide past each other along fractures.
- Associated with earthquakes.
- Predominantly found on ocean floor; some on land (e.g. San Andreas Fault).

Earthquakes and volcanoes often found at plate boundaries.
Earthquakes:
- Occur when stress overcomes a locked fault, releasing energy.
- Can generate tsunamis if under the ocean.
Volcanoes:
- Occur at divergent boundaries, subduction zones, or hot spots.
- Hot spots: Areas in the mantle creating volcanic activity (e.g. Hawaiian Islands, Yellowstone National Park).

Soil: Mixture of eroded rock, mineral nutrients, organic matter, water, air, and organisms.
Essential base of life on land:
- Absorbs nutrients for plants, purifies water, aids decomposition, critical in biogeochemical cycles, helps reduce CO2.
Renewable Resource:
- Slowly renewed but faces erosion challenges.
- Caused by wind or water.

Mature Soil Formation:
- Occurs during primary succession.
- Developed from weathered parent material.
- Features distinct layers called soil horizons.
- Most mature soils have at least three horizons.
- Cross-sectional view of horizons is known as soil profile.

Water Holding Capacity: Varies with soil type, crucial for land productivity and fertility.
Porosity: Amount of spaces/pores in the soil.
Permeability: Water movement ability through soil.
Fertility: Measure of nutrients, relates to plant growth productivity.
Soil Texture: Sizes/amounts of particles: sand, silt, clay.

Soil Triangle: Diagram for identifying soil types based on sand, silt, and clay percentages.
Clay: Smallest and finest particles.
Sand: Largest and coarsest particles.