Layers of the Earth and Tectonic Plates

Layers of the Earth

• Crust: Outermost, thinnest layer (50km), composed of different landforms.
• Mantle: Beneath the crust, thickest layer (2900km), solid rock. Contains the asthenosphere.
• Outer Core: Liquid layer, composed of iron and nickel (2200km), 5000°C.
• Inner Core: Solid, densest layer (1200km), 6000°C.

Tectonic Plates

• Tectonic Plates: Large sections of rock within the lithosphere.
• Plate Boundaries: Where two plates meet.
• Plate Tectonic Theory: Earth's crust is made up of moving plates driven by convection currents in the mantle.
• Types of Plate Movement: Plates can move towards each other (convergent), away from each other (divergent), or slide past each other (transform).

Types of Tectonic Boundaries

• Convergent (Destructive): Two plates move together, one may be driven down into the mantle (subduction).
• Divergent (Constructive): Two plates move apart.
• Transform (Conservative): Two plates slide past each other.

Earthquakes

• Active Faults: Generated earthquakes in the past 10,000 years; may still generate earthquakes.
• Inactive Faults: Show no signs of generating earthquakes in the past 10,000 years; may potentially generate earthquakes in the future.
• Earthquake Causes: Sudden movement along fractures in the Earth's crust known as faults, releasing energy from beneath the ground.
• Intensity: Measure of damage caused by an earthquake.
• Magnitude: Total amount of energy released by the earthquake.
• Faults: Fractures or breaks in the earth's crust where earthquakes are likely to occur.
• Types of Faults: Vertical movement (dip-slip) such as normal, reverse, thrust faults and horizontal movement (strike-slip) such as left lateral, right lateral and oblique-slip faults.

Seismic Waves

• Seismic Waves: Waves of energy caused by the sudden breaking of rock within the earth.
• Types of Seismic Waves: Body waves (travel through the Earth's interior: P-waves and S-waves), and Surface waves (travel on Earth's surface: Love waves and Rayleigh waves). Body waves arrive first, followed by surface waves, which cause the most damage.

Measuring Earthquakes

• Mercalli Scale: Measures intensity of an earthquake based on the observed effects.
• Richter Scale: Measures the magnitude of an earthquake; logarithmic scale.
• Seismogram: A record of ground motion during an earthquake, used to determine magnitude and type of earthquake.
• Seismograph: Instrument used to measure earthquake waves.