Plate Tectonics

Introduction
The Theory of Plate Tectonics explains how and why crustal plates move around the Earth. It also explains why the Pacific Ocean has so many volcanoes, large earthquakes and tsunamis. It gives us a basic understanding of how our planet is changing. It explains how mountains form, why crustal plates move and where great earthquakes are likely to strike.

Icy crevasse on Iceland, Photo by Sarah Masters

Icy crevasse on Iceland, Sarah Masters

Plate boundaries
Seismologists discovered earthquake zones around large blocks of the Earth's crust. They found a divergent boundary formed when plates separated. Some plates form a transform boundary when they slip past each other.

Subduction zones
Scientists discovered a convergent boundary developed where  crustal plates converged forming a subduction zone. Scientists also discovered that ocean trenches formed at convergent boundaries in subduction zones.

The Pacific Plate
The Pacific Plate contains the largest ocean on Earth. Crustal plates are converging on the Pacific Plate creating subduction zones where great earthquakes occur. The Nazca Plate and Pacific Plate are converging. The earthquake epicenter of a magnitude 9.5 earthquake occurred in the subduction zone between these two plates.

Mid ocean ridges 
The Mid-Atlantic Ridge is a mid ocean ridge that runs down the middle of the Atlantic Ocean. Plate movements along the ridge produce small earthquakes that produce P waves and S waves as basalt lava pours out of fissures on the ocean floor. Iceland sits on the Mid-Atlantic Ridge over a hot spot. The picture above shows a rift valley that forms on ocean floors where crustal plates are separating.

More Plate Tectonic Links

Plate Movements Moving plates on our planet converge, separate and slide past each other.

Nazca Plate This plate converges with the Pacific Plate producing very large earthquakes off the coast of Chile.

Thrust Faults These faults occur where large blocks of land can be forced over the top of another block of land at a low angle.

Divergent Boundary These boundaries form the global mid-ocean ridge system which is the largest mountain chain on Earth.


Crustal Plates There are large and small plates that cover the Earth. Subduction zones form where these plates are recycled.

Mid Ocean Ridge The global mid-ocean-ridge system is the longest chain of mountains on Earth and was not discovered until the 20th Century.

Earthquake Epicenter The epicenter of an earthquake is a point on the Earth's surface, not where the earthquake originates.

Caribbean Plate This plate is small but very complex. It has a subduction zone, transform fault, and triple junction.


What is an Earthquake Find out what causes the Earth to shake, rattle and roll during an earthquake. 

Convergent Boundary There are two types of boundaries where plates converge. They produce great mountain ranges and large earthquakes.

Transform Boundary  These boundaries are found all around our ocean floors where oceanic plates are separating.

Pacific Plate The Pacific Plate is the largest plate on Earth. Great earthquakes and towering volcanoes surround the plate along the Pacific Ring of Fire.


Ocean Trenches Find out how plates diving beneath other crustal plates create trenches on the ocean floor that are deepest points on Earth.

S Waves Find out about S waves and how they are produced and travel through the Earth.

Plate Tectonics Find out lots of fascinating facts and interesting trivia on plate tectonics.

Kids Fun Science The links on our home page include information about volcanoes, science activities, plate tectonics, the rock cycle and much more