The Rock Cycle- What is it?

The rock cycle is one of the fundamental principles of geology, and one I have neglected to explain until now. The rock cycle describes how rocks weather; that is to say breakdown, erode, and change over time. There are three end member parties in this cycle. these include igneous rocks, sedimentary rocks and metamorphic rocks.

Here is a cool video explaining how each of the different rock types are formed, it works well in conjunction with my blog post.

Igneous Rocks: Igneous rocks are rocks that form when magma or lava cools, these rocks typically contain crystals from varying minerals depending on the type of rock. Below is a close up image of the igneous rock Granite.

Sedimentary Rocks: Sedimentary rocks are formed from pieces of broken or weathered igneous or metamorphic rock cemented together in some way, usually involving some kind of mud. This rock fragment mud mix is then lithified, which is the process of turning sediment (broken off rock chunks) or other material into stone. Sedimentary rocks usually occur along beaches and river banks, the most common sedimentary rock being sandstone. Below is a picture of the sedimentary rock sandstone.

Metamorphic Rocks: Metamorphic rocks form when either sedimentary or igneous rocks are subject to extreme heat and pressure, causing the rock to bend and warp. This often gives metamorphic rocks a “banded” or “wavy” appearance. Metamorphic rocks are the result of the pressures and temperatures associated with the tectonic and Orogenic events written about in my previous blog posts. Only the movement of such massive slabs of rock can provide the necessary pressure and heat to bend rocks in this way. Below is a picture of the metamorphic rock Gneiss which is formed from granite, notice the “bands” along its surface.