 Sedimentary rocks, what are they? Where are they come from and how do they form? By the end of this video you'll have an answer to all of these questions that you've been burning to know. So let's get started. Sedimentary rocks you can think of as the product of Earth's natural recycling system. It takes broken down pieces of other rock and puts it together to form a whole new rock. So maybe you haven't wondered this before, but where did the sediment really come from and how did it get there? So what happens is you take an existing rock and you weather it. You might have seen some scraggly looking rocks on the side of the road. These are currently undergoing weathering from processes such as wind and water. Eventually these scraggly looking rocks get eroded and transported downstream. And this transportation can happen through wind or water. Eventually these little pieces of rock or sediment get deposited and eventually lay it up on top of each other. As these eventually get buried further and further down into our crust, they're subjected to intense heat and pressure forming the compaction and cementation of these rocks to form what we know as a cohesive sedimentary rock. Something you can pick up and hold rather than pick up and crumble through your fingers. So Earth's surface doesn't resemble a marble. It's not solid rock all around us. We've got a layer of unconsolidated material or sediment, which is handy because we need that for things such as trees to grow so we can breathe. But where does all this sediment come from? Well let's consider a grain of sand. Let's call her sandy. She's lying lazily on a beach and she enjoys this sun baking session because she's had a long and chaotic journey to get there. She's undergone weathering, erosion and transport. So she was first separated from her friends in a rock, transported downstream with other sediments banging into each other and eventually deposited on the beach front. These processes of weathering, erosion, transport and deposition occur throughout geological time. And what that does is it creates layers of sedimentary buildup. These layers eventually become buried under more and more layers which are getting deposited. They get compacted, cemented and turned into sedimentary rock. The compaction and cementation of individual grains creates plastic sedimentary rocks which means that the sedimentary rocks is made up of individual grains cemented together. There are two other types of sedimentary rocks which we can discuss which are chemical and organic sedimentary rocks. Organic sedimentary rocks are formed in a very similar way. We get an accumulation of matter which is buried, compacted and turned into rock. Whereas chemical sedimentary rocks are formed in a slightly different way. These are formed through the precipitation of minerals from solution. For example, limestone in deep marine sediments. The chemicals in the solution precipitate out to form new minerals. So in summary, sediment is created by weathering and eroding existing rocks. The sediment is then transported downstream and deposited to form plastic or organic sedimentary rocks. A third rock type chemical sedimentary rocks is formed by the precipitation of minerals out of solution.