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TITLE: The Solar System

Plate Tectonics
Welcome to the greatest show on Earth. Propelled by intense heat simmering beneath the crust, Earth’s surface is dramatically reshaping itself in an endless, slow-motion ballet called plate tectonics. Its huge, rocky plates separate, collide, and slide past each other causing earthquakes, feeding volcanic eruptions, and raising mountains.

[Photo Link: Orientation Theater]
Orientation Theater

[Photo Link: Geological Revolution]
Geological Revolution

[Photo Link: The Ancient Continents]
The Ancient Continents

[Photo Link: The Inner Earth]
The Inner Earth

[Photo Link: The Unreachable Frontier]
The Unreachable Frontier

Plates Move Apart
Hidden beneath the seas, along a global system of mountain ridges, Earth’s plates are growing and spreading apart. Each year these oceanic spreading ridges erupt more than three times as much molten rock as do all the volcanoes on land. Magma rises from Earth’s mantle at spreading ridges and cools on and beneath the ocean floor, adding to the plates on either side. The growing plates inch away from the ridges—widening ocean basins and rafting apart entire continents.

[Photo Link: Mid-Atlantic Ridge]

[Photo Link: Juan de Fuca Ridge]
Juan de Fuca

Plates Come Together
Where plates come together, or converge, we see some dramatic manifestations of plate tectonics. At convergent margins, continents grow as plates are consumed.

[Photo Link: Cascade Range]
Cascade Range

[Photo Link: The Himalaya]
The Himalaya

Plates Pass By
Why do earthquakes shake California? The state straddles two plates that are moving past each other like trains on opposite tracks. The plate boundary is marked by a zone of active faults—breaks in the rock and ground surface caused by plate movements. The most famous of these is the 1200-km (750-mi) long San Andreas Fault. The San Andreas fault is a transform fault, a kind common on the sea floor but rarely found on land.

[Photo Link: San Andreas Fault]
San Andreas Fault

[Photo Link: Earthquakes]

Volcanoes & Hot Spots
Vivid reminders that our planet is geologically active, volcanic eruptions are generated by the same heat engine that drives Earth's plates. Volcanoes form at places where large quantities of heat escape at the surface—sometimes quite dramatically. Earth's volcanoes vary widely in size, form, and explosivity. Some erupt violently, others pour out rivers of lava. This diversity is largely related to their plate-tectonic environments.

[Photo Link: Volcano Profiles]
Volcano Profiles

[Photo Link: Inside an Active Volcano]
Inside an
Active Volcano

[Photo Link: Tracking Volcanoes]
Tracking Volcanoes

[Photo Link: Above Hot Spots]
Above Hot Spots

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Smithsonian National Museum of Natural History Department of Mineral Sciences website Credits