Plates

=Distribution =

The Earth's crust is broken up into pieces called plates. Plates move do to the movement of the molten rock beneath the earth's crust. (the mantel)



There are two types of plates.

**1) Oceanic plate** - a plate with a ocean. This plate is heavier than a continental plate so it sinks beneath it.

**2) Continental plate** - A plate with land. This is lighter than an oceanic plate and therefore it never sinks.

This diagram shows the earths' main plates. The lines show the plate boundaries.



Earthquakes and volcanoes occur in narrow bands along the plate boundaries. There are four types of plate boundariy.
 * 1) Constructive. **

When two oceanic plates move apart new land is formed between them under the ocean. 


 * 2)Destructive. **

When an oceanic and a continental plate meet the oceanic is forced down under the continental plate.  This is where most volcanoes occur.



Where two plates slide against each other causing earthquakes.
 * 3) Conservative **



**<span style="color: #800080; font-family: Tahoma,Geneva,sans-serif; font-size: 120%;">Rin﻿g﻿ of Fire ** <span style="color: #292999; font-family: Tahoma,Geneva,sans-serif; font-size: 16px; line-height: 24px;">The Ring of Fire is surrounded by the Pacific Plate, which is surrounded by the Pacific Ocean. It contains more than half of the world’s volcanoes. Some of the world’s famous volcanoes are in this fantastic ring in the ocean. The existence is explained by plate tectonics. <span style="color: #292999; font-family: Tahoma,Geneva,sans-serif; font-size: 16px; line-height: 24px;">The Ring of Fire is on one of the plates of the earth’s crust. Newly-formed magma rises to the air of the earth’s surface and erupts, forming chains of these violent volcanoes, like the Ring of Fire. <span style="color: #292999; font-family: Tahoma,Geneva,sans-serif; font-size: 12pt;">The Ring of Fire is very big. It stretches from New Zealand to Alaska and eastern Asia to North and South America. The Ring of Fire also produces heavy seismic activity. Frequent earthquakes are also very common in the Ring of Fire.

**<span style="color: #800080; font-family: Tahoma,Geneva,sans-serif; font-size: 120%;">Subduction Zones **


<span style="color: #292999; font-family: Tahoma,Geneva,sans-serif; font-size: 120%;">Subduction areas develop when a continental crust pushes against a plate with an oceanic crust. The heavier oceanic crust bends and begins moving downward toward the upper mantle. The oceanic plate is pulled downward by gravity. The edge of the plate begins to melt due to friction as it moves deeper into the Earth until it is recycled in the upper mantle. The magma, molten rock, is lighter and less dense than the surrounding rock so it is buoyant. The magma feeds the volcanoes that form in subduction zones.



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