science study guide

Earth's Layers Overview

• Earth's Composition: Layers classified by composition and properties.

  • Crust: Solid outer layer (Silicon, Oxygen, Aluminum).

  • Mantle: Ductile solid below crust (Silicon, Oxygen, Magnesium).

  • Outer Core: Liquid (Nickel, Iron).

  • Inner Core: Solid due to pressure (Nickel, Iron).

• Mechanical Properties:

  • Lithosphere: Crust and upper mantle, brittle, tectonic plates.

  • Asthenosphere: Ductile solid in upper mantle.

• Tectonic Plates:

  • Continental Crust: Less dense, granite, ~4 billion years old.

  • Oceanic Crust: Denser, basalt, ~200 million years old.

• Plate Boundaries:

  • Divergent: Plates move apart (mid-ocean ridges).

  • Convergent: Plates collide (oceanic-continental forms trenches/volcanoes).

  • Transform: Plates slide past (e.g., San Andreas Fault).

Key Processes Driving Plate Movement

• Slab Pull: Subducting plate pulls trailing slab.

• Ridge Push: Elevated ridges push plates away.

• Locations: Active margins (earthquakes, volcanism) vs. passive margins (stable).

• Faults and Earthquakes:

  • Types of Faults: Normal (tension), Reverse (compression).

  • Seismic Events: Result from friction and energy release.

Earthquake Fundamentals

• Magnitude: Measured by Moment Magnitude Scale; intensity grows with each level.

• Types of Seismic Waves: P-waves (solids/liquids), S-waves (solids), Surface waves (most damage).

• Measuring Earthquakes: Seismographs and triangulation methods.

Geologic History

• Divisions: Eons, eras, periods marked by significant events.

  • Precambrian Era: Origin of Earth and life.

  • Paleozoic Era: Age of Fish and major geological changes.

Volcanoes

• Definition: Opening in the crust for lava, ash, gases to escape.

• Classification: Active, dormant, extinct.

• Formation Locations: Divergent/convergent boundaries, hot spots.

• Magma Types: Rhyolitic (explosive), andesitic (intermediate), basaltic (least explosive).

• Eruption Effects: Ash can block sunlight leading to potential famines.