Creation of Igneous Rocks
Magma, the hot molten mixture of rocks, minerals and other substances found under the Earth’s crust can find its way up and consequently cool down to solidify. This solidified form of magma is what we called igneous rock. The shape of igneous rocks depend on whether the magma moves upwards through the earth’s crust, spreads out over it or moves horizontally under it.
Creation of Metamorphic Rocks
Metamorphic rocks are created due to extreme pressure and temperature. Igneous rocks which are under the earth’s surface can be subjected to a lot of pressure from the layers on top and over time change into metamorphic rocks. Likewise, when the molten magma seeps through the crust, the extreme temperature can change the composition of surrounding rocks.
Creation of Sedimentary Rocks
Sedimentary rocks are basically rocks that are formed by sediments or pieces that break off from other rocks. The natural processes of weathering and erosion play a huge role in the creation of these rocks. When Igneous or Metamorphic rocks are exposed, atmospheric elements act on them, weakening them and breaking them gradually. The smaller pieces can then be washed away by water and usually collect at the bottom of rivers and seas, forming bigger rocks over time.
The continuous cycle
Since the earth’s crust is made up of tectonic plates which are in motion, spreading ridges and subduction zones keep the rock cycle going. New rocks are formed when magma swells up and cools down, while existing ones undergo subduction at plate boundaries and are converted into magma once again.
The whole cycle restarts when magma converts into igneous rocks, which can then form metamorphic or sedimentary rocks, before they are reconverted into magma. There is no strict sequence to the cycle however, and sedimentary rocks can also be converted into metamorphic rocks if they under go extreme pressure.