• Crust: Thin, solid outer layer; includes continental and oceanic crust.

• Mantle: Semi-solid, convection currents cause plate movement.

• Outer Core: Liquid iron and nickel, generates Earth’s magnetic field.

• Inner Core: Solid due to high pressure, mostly iron and nickel.

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Layers of the Earth

• Earth’s crust is divided into large pieces called tectonic plates.

• Plates float on the semi-solid mantle.

• Plates move due to convection currents in the mantle.

• Major plates include the Pacific, North American, Eurasian, and Australian plates.

Tectonic Plates

• ​Located around the edges of the Pacific Ocean.

• A major area of tectonic activity: earthquakes, volcanoes, and mountain-building.

• Convergent boundaries dominate, with many subduction zones.

• Home to 75% of the world’s active volcanoes and most of its earthquakes.

• Famous locations include Mount Fuji (Japan), and Mount St. Helens (USA)

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Ring of Fire

• Plates move apart

• New crust forms

• Can cause volcanoes and earthquakes

• Example: Mid-Atlantic Ridge

Plate Boundaries: Divergent

• Plates move together.

• One plate may be forced under another (subduction)

• Forms mountains, trenches, and volcanoes

• Example: Himalayas (includes Everest)

Plate Boundaries: Convergent

• Plates slide past each other

• Causes earthquakes

• Examples:

Plate Boundaries: Transform

• San Andreas Fault (North American and Pacific plates)

• Alpine Fault (Pacific and Australian plates in NZ)

• Caused by sudden movement of tectonic plates.

• Measured using the Richter scale and seismographs.

• Focus: Point inside Earth where the earthquake starts.

• Epicentre: Point on the surface directly above the focus.

• Common at all types of plate boundaries.

Earthquakes

• Occur at convergent and divergent boundaries or over hotspots

• Pressure builds up, causing an eruption

• Magma rises to the surface, forming lava when it cools

• Example: Mount Vesuvius (destroyed Pompeii)

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Volcanoes

Formed from cooled lava or magma

e.g. basalt, granite, pumice, obsidian

Igneous

Formed from compacted sediments
e.g. sandstone, limestone, shale

Sedimentary

Formed by heat and pressure underground
e.g. marble from limestone, slate from shale

Metamorphic

The Rock Cycle