Why does mantle melt at divergent margins

In continental rifts, magma rising through the thicker continental crust is much-modified, resulting in a wide variety of volcanic activity. They form where a slab of old, cold, dense oceanic lithosphere sinks back into the mantle.

As the descending plate heats up, water is released from the ocean-floor rocks; this lowers melting points in the adjacent mantle rock crustal rock may also melt forming thick, sticky andesite magma, rich in dissolved volatiles which, on reaching the surface, has a nasty tendency to erupt explosively. Heat within the asthenosphere creates convection currents that cause tectonic plates to move several centimeters per year relative to each other.

If two tectonic plates collide, they form a convergent plate boundary. Usually, one of the converging plates will move beneath the other, a process known as subduction. Deep trenches are features often formed where tectonic plates are being subducted and earthquakes are common. As the sinking plate moves deeper into the mantle, fluids are released from the rock causing the overlying mantle to partially melt. Locations with converging in which at least one plate is oceanic at the boundary have volcanoes.

Melting at convergent plate boundaries has many causes. The subducting plate heats up as it sinks into the mantle. Also, water is mixed in with the sediments lying on top of the subducting plate. As the sediments subduct, the water rises into the overlying mantle material and lowers its melting point. Melting in the mantle above the subducting plate leads to volcanoes within an island or continental arc. Why does melting occur at convergent plate boundaries? This water lowers the melting point of the mantle material, which increases melting.

Volcanoes at convergent plate boundaries are found all along the Pacific Ocean basin, primarily at the edges of the Pacific, Cocos, and Nazca plates. Trenches mark subduction zones, although only the Aleutian Trench and the Java Trench appear on the map in figure 1. Remember your plate tectonics knowledge. Large earthquakes are extremely common along convergent plate boundaries.

Of course, these volcanoes are caused by the abundance of convergent plate boundaries around the Pacific. Figure 1. The Cascade Range is formed by volcanoes created from subduction of oceanic crust beneath the North American continent.

The Pacific Ring of Fire is where the majority of the volcanic activity on the Earth occurs. A description of the Pacific Ring of Fire along western North America is a description of the plate boundaries.

Volcanoes in Africa. List and map of all volcanoes in Africa. Most volcanoes are located in the Great Rift Valley, but there are more. Methana 28 Mar - 4 Apr Land of Theseus The Saronic Gulf opposite Athens is one of the most beautiful and interesting areas of Greece, full of beautiful landscapes, small towns, islands, archeological remains and one of Europe's least known active volcanic areas.

Join us on a relaxing tour to discover this fascinating area!