Archive for June 23rd, 2011

PLATES ARE CREATED

http://www.moorlandschool.co.uk/earth/tectonic.htm

In the diagram below you can see that the continental crust is beginning to separate creating a diverging plate boundary. When a divergence occurs within a continent it is called rifting. A plume of hot magma rises from deep within the mantle pushing up the crust and causing pressure forcing the continent to break and separate. Lava flows and earthquakes would be seen. In the diagram below you can see that the continental crust is beginning to separate creating a diverging plate boundary. When a divergence occurs within a continent it is called rifting. A plume of hot magma rises from deep within the mantle pushing up the crust and causing pressure forcing the continent to break and separate. Lava flows and earthquakes would be seen.

diverge plates with opening rift valley animation.gif (18569 bytes) As the rift valley expands two continental plates have been constructed from the original one. The molten rock continues to push the crust apart creating new crust as it does.
diverge plates animation.gif (16916 bytes) This is an example of a divergent plate boundary (where the plates move away from each other). The Atlantic Ocean was created by this process. The mid-Atlantic Ridge is an area where new sea floor is being created.
diverge3 animation  widening ocean.gif (17635 bytes) As the rift valley expands, water collects forming a sea. The Mid-Atlantic Ridge is now 2,000 metres above the adjacent sea floor, which is at a depth of about 6,000 metres below sea level.
diverge4 animated sequence.gif (25011 bytes) The sea floor continues to spread and the plates get bigger and bigger. This process can be seen all over the world and produces about 17 square kilometres of new plate every year.

TECTONIC PLATES

Primary plates

These seven plates comprise the bulk of the seven continents and the Pacific Ocean.

Secondary plates

These smaller plates are generally shown on major plate maps, but with the exception of the Arabian plate do not comprise significant land area.

Tertiary plates

Tertiary plates are grouped with the major plate that they would otherwise be shown as part of on a major plate map. Mostly these are tiny microplates, although in the case of the Nubian-Somalian and Australian-Capricorn-Indian plates these are major plates that are rifting apart. Some models identify more minor plates within current orogens like the Apulian, Explorer, Gorda, and Philippine Mobile Belt plates. The remainder of the tertiary plates are the dwindling remains of much larger ancient plates. There may or may not be scientific consensus as to whether a tertiary plate is a separate plate yet, is still a separate plate, or should be considered a separate plate, thus new research could change this list.[1][2][3][4]

http://en.wikipedia.org/wiki/List_of_tectonic_plates