What a tectonic plate is
One or more types of tectonic plate activity
the results of the tectonic activity
Project 1: Tectonic Plates
Plate Tectonics
Scientists which are known as oceanographers have been able to measure, and map out the ocean floor. What these scientists have discovered has helped explain how it is that continents are able to move around on the Earth’s crust.
Deep beneath the waves, at the surface of the ocean, located almost exactly halfway between the continents are raised areas known as ridges. These ridges are similar to under-water mountain ranges. At other locations we find extremely deep trenches, some reaching many thousands of feet in depth.
Many scientists believe that the ridges represent areas where new crust is being formed, as hot magma escapes from the Earth’s core, and spreads outward. As the seafloor spreads outward, away from the area where magma is being released, the continents are carried across the sea, riding on top of the sima crust.
http://www.kidsgeo.com/geology-for-kids/0043-plate-tectonics.php
The different plates
It is believed that the crust, beneath the oceans as well as the continents, together with the upper part of the mantle is divided into huge slabs called plates. The movement of the plates is explained by the earlier theory of Continental Drift.
There are eight identified major plates plus an assortment of smaller ones. The major plates include
- the Eurasian plate,
- the African plate,
- the North American plate,
- the South American plate,
- the Antarctic plate,
- the Indoaustralian plate,
- the Pacific plate
- The Nazca plate.
(Fig 1.10) Major plates of the world.
Figure 1.10 the different plates on the world map, which shows that the plates are capped by both the oceanic and continental crust.
http://library.thinkquest.org/17457/platetectonics/3.php
Tectonic plate interaction
There are three different basic types of tectonic plate interactions:
• Divergent boundaries are areas where plates move away from each other, forming either mid-oceanic ridges or rift valleys.
• Convergent boundaries are areas where plates move toward each other and collide. These are also known as compressional or destructive boundaries.
o Subduction zones occur where an oceanic plate meets a continental plate and is pushed underneath it. Subduction zones are marked by oceanic trenches. The descending end of the oceanic plate melts and creates pressure in the mantle, causing volcanoes to form.
o Obduction occurs when the continental plate is pushed under the oceanic plate, but this is unusual as the relative densities of the tectonic plates favours subduction of the oceanic plate. This causes the oceanic plate to buckle and usually results in a new mid ocean ridge forming and turning the obduction into subduction
o Orogenic belts occur where two continental plates collide and push upwards to form large mountain ranges.
• Transform boundaries occur when two plates grind past each other with only limited convergent or divergent activity.
The result of the tectonic activity
Convergent Boundaries
Converge is a large word that scientists use to describe two objects that come together. In the case of plate tectonics, the two objects coming together are large plate-like pieces of the Earth’s crust. As these two plates push against each other, one is ultimately forced down beneath the other.
When this happens near land, we see the earth above the two meeting plates rise, forming spectacular mountain ranges. A parallel oceanic trench typically forms just off the shore, as one plate descends deep into the Earth’s core.
These convergent boundaries commonly cause volcanoes to form, as old crust melts. As two plates rub against one another, a number of small and large earthquakes are common near convergent boundaries.
http://www.kidsgeo.com/geology-for-kids/0046-convergent-boundaries.php
Transform Boundaries
The final type of boundary is one where the two plates slide against each other in a sideways motion. These boundaries between plates is referred to as transform boundaries. As two plates slide past one another, in a transform boundary, neither plate is added to at the boundary, nor destroyed.
The result of two massive plates pushing against one another is that massive amounts of energy build up. Occasionally this energy is released suddenly in the form of large earthquakes.
http://www.kidsgeo.com/geology-for-kids/0047-transform-boundaries.php
Divergent Boundaries
The word diverge is a big word used by scientists to describe what happens when two objects move away from each other. Thus, a divergent boundary is a boundary where two tectonic plates are moving away from one another. As we have already discussed, this most often takes place at ocean ridges.
These ridges are zones of intense volcanic activity. In addition to forming at the bottom of oceans, these divergent boundaries can also form on continents. When this happens, a line of volcanoes emerges.
http://www.kidsgeo.com/geology-for-kids/0045-divergent-boundaries.php
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