Geology of Earth Layers

Lithosphere

• Rigid outer layer of Earth, consisting of the crust and upper mantle, averaging 100 - 250 km in thickness.
• Composed of moving tectonic plates, responsible for features like ocean basins, continents, and mountain ranges.

Asthenosphere

• Semi-fluid layer beneath the lithosphere, located between 100 - 650 km in depth within the upper mantle.
• Hot and capable of flowing both vertically and horizontally, described as "plastic" due to its deformable nature.

Lower Mantle

• Rigid layer situated between 650 - 2900 km deep, where rocks are extremely hot and can gradually flow.
• Heat from Earth's core drives gravitational convection within the mantle.

Earth's Core

• Outer Core: Liquid layer primarily made of iron-nickel alloy, generating Earth's magnetic field through convective flow.
• Inner Core: Solid and dense, with properties akin to iron-nickel meteorites.

Geological Processes

• Breakup of Pangaea began approximately 200 million years ago.
• Mesosaurus fossils found on both South American east coast and African west coast indicate historical land connections.

Plate Movement

• Earth's surface moves at a rate of approximately 10 cm per year.
• Significant movements occur within the lithosphere and asthenosphere.
• There are seven major tectonic plates globally.

Types of Crust

• Continental crust is primarily composed of granite, while oceanic crust consists mainly of basalt.

Plate Boundaries

• Divergent Plate Boundary: Plates move apart, typically creating new crust.
• Convergent Plate Boundary: Plates collide, resulting in upward land formation, such as mountain ranges.
• Transform Plate Boundaries: Plates slide past each other, commonly resulting in earthquakes, e.g., the San Andreas Fault in California.

Future Predictions

• Los Angeles and San Francisco may eventually be positioned on top of each other due to tectonic movements.

Minerals and Rocks

• Minerals serve as the fundamental building blocks of rocks, with over 3,000 varieties available.
• Key characteristics of minerals include:
  • Existence as solid under Earth’s normal conditions.
  • Naturally occurring formation.
  • Inorganic substances.
  • Fixed chemical formulas with specific elemental combinations.
  • Specific atomic structures.

Identifying Minerals

• Identification based on properties such as:
  • Hardness: Ability to scratch or be scratched, measured using Mohs’ Hardness scale.
  • Lustre: Surface light reflection, categorized into metallic and nonmetallic types.
  • Cleavage/Fracture: The way minerals break or split.
  • Streak: Color of the powdered residue when a mineral is scratched on a surface.

Rock Cycle

• Rocks are solid mixtures of one or more minerals or organic matter, classified by formation, composition, and texture.
• Rocks undergo transformation over time via the rock cycle, emphasizing continuous geological activity.
• Marble consists of a single mineral (calcite), while granite includes multiple minerals such as quartz, feldspar, and mica.