Geology Chapter: Volcanic Features and Earth's Layers

Volcanic Features

• Intrusive volcanic features arise when molten rock cools before reaching the surface.
• Magma creates pathways through weaknesses in the crust, causing it to widen from a few centimeters to tens of meters.
• Example of intrusive feature: Sill - formed by magma flowing horizontally between rock layers.

Earth's Layers

• Mantle: The layer between the crust and core; constitutes 82% of Earth’s volume and extends to about 2900 km depth with temperatures exceeding 1200°C.
• Core: The innermost layer, characterized by extreme density and heat; temperature at the center reaches approximately 5500°C, lying about 6400 km below the surface.

Plate Tectonics

• Study of the Earth's crust movement and its effects on landforms.
• Plates are rigid segments that float on semi-molten rocks, driven by convection currents formed by heat distribution.
• Three plate boundary types: Convergent, Divergent, and Transform.

Plate Boundaries

• Convergent Boundaries: Associated with volcanoes, deep ocean trenches, and island arcs.
• Divergent Boundaries: Characterized by shallow earthquakes, volcanic eruptions, rift valleys, and ocean ridges.
• Transform Boundaries: Result in earthquakes as plates slide past each other, creating ridges and valleys.

Continental Drift

• Refers to the gradual movement of continental masses across the Earth's surface.
• Evidence includes:
  • Continent shapes appearing as jigsaw puzzle pieces.
  • Identical land-based fossils on separated continents.
  • Similar age and type rocks found at continental edges.
  • Shared characteristics among species across different continents.

Earth's Crust

• The solid outer layer, accounting for about 1/60 of Earth's volume.
• Depth ranges up to 5 km below oceans and 65 km beneath continents.
• Two types:
  • Continental Crust (sial): Rich in silica (Si) and aluminum (Al).
  • Oceanic Crust (sima): Predominantly basalt, with silica (Si) and magnesium (Ma).

Rock Cycle

• Earth’s crust rocks continuously change through processes like weathering, erosion, transportation, and deposition.
• Three main rock types:
  • Igneous Rocks: Formed from cooling magma, found at plate boundaries; examples include granite and basalt.
  • Sedimentary Rocks: Evolved from cycles of deposition and compaction; examples include shale and limestone.

Additional Notes on Plate Boundaries

• Divergent Boundaries result in new crust formation, known as constructive margins.
• Transform Boundaries feature plates sliding alongside each other, like the San Andreas Fault, where no volcanism occurs due to lack of magma movement.