Plate tectonics essay
Tectonic processes have been responsible for the major landforms across the Earth’s surface. These processes are controlled by the convection currents rising from the Earth’s mantle.
Firstly, one place where tectonic activity occurs is at oceanic to oceanic constructive plate boundaries. Here two plates diverge or move away from each other, pushed apart by huge convection currents In the earth’s mantle. These convection currents are initiated by heat energy produced from radioactive decay in the earth’s core. As the convection currents move the plates away from each other, there is a weaker zone in the crust and an …show more content…
These Japanese island arcs extend 3000km and magma produced under them form felsic plutonic rocks (granite), some of which erupts on the surface to make volcanoes. Large-scale formation of granites develops the crust of island arc.
On the other hand, some tectonic activity doesn’t produce any landform. An example is at the San Andreas Fault. Although both plates are moving in a north westerly direction, the pacific plate Is moving faster than the north American plate (7cm/year faster), so the relative movement of the north American plate is to the south east. The pacific plate is being moved northwest due to the sea floor spreading from the pacific coast rise in the gulf of California. The North American plate is being pushed west and north due to sea floor spreading of the mid-Atlantic ridge. Movement is sporadic and jerky. Frictional forces lock the blocks of lithosphere together for years at a time. When frictional forces are overcome, the plates slip and shallow focus earthquakes are generated.
Similarly, landforms can be produced without the source of tectonic activity. The Hawaiian islands are not connected with any plate boundary. The volcanic area is caused by a localized hotspot beneath the pacific plate. A concentration of radioactive elements inside the mantle may cause such a hotspot to develop. From this, a plume of magma rises to eat into the plate above the hotspot.