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Divergent Boundaries

Earth’s tectonic plates move, and they move a LOT. But, their movements vary. The movement occurs along plate boundaries (where two plates meet). When tectonic plates pull away from each other, they are diverging. Therefore, we call the lines where two plates separate divergent boundaries.
Thingvellir Valley in Iceland

Check out this valley! The two plates are pulling away from another creating a valley between the plates.

How Divergent Boundaries Occur

The reason plates move in the first place is because of convection currents. Convection currents occur in the earth’s mantle, where there is molten rock (also called magma). The tectonic plates sit on top of the mantle.
 
Convection currents move in a circular pattern. Sometimes the currents rise and then move in opposite directions. This causes the plates above to separate.

What Happens When Plates Pull Apart

Several things can result from divergent boundaries. Depending on where the boundary is, either a valley or a mid-ocean ridge can occur.
 
Valleys form when plates pull apart above water. The earth’s crust thins as it is pulled in opposite directions. This creates a region where the crust is lower than surrounding areas. This area usually fills with water, forming a river. We call these continental divergent boundaries.
Types of plate boundary earthquake

There are three types of plate movements. Can you see how divergent plates pull away from each other?

 
If the crust is stretched thin enough, pieces of land can break off from one another. When this happens, an island is created.
 
If a divergent boundary occurs under the surface of water, it creates a ridge. Ridges are what cause the ocean floor to spread. When plates pull away, they allow the mantle’s molten rock to rise. The molten rock fills the gap, spreads, and then hardens. As this process repeats, the ocean floor expands. This is known as an oceanic divergent boundary.

Rift Valley

The most well known divergent boundary is the Great Rift Valley. It is a continental divergent boundary in Africa that runs 4,000 miles long. The Great Rift Valley includes some of Africa’s most important geographical features such as the Dead Sea, the Jordan River, and the Red Sea. A vast number of volcanoes and hot springs are scattered all along the valley.

Mid-Atlantic Ridge

The biggest oceanic divergent boundary is the Mid-Atlantic Ridge. This ridge divides the Atlantic Ocean in two places: between the North American and the Eurasian plates in the north and the South American and African plates in the south. It contributes to seafloor-spreading and is what most likely causes continental movement.

Other Great Resources

Kids Fun Science on Divergent Boundaries: http://www.kids-fun-science.com/divergent-boundary.html
 
Mid-Atlantic Ridge: 

 
 
Plate Tectonics: 

 Written by: Anna Hylen.