Why Do Sediments Form Layers?
Sediments are materials that are broken down by natural process such as water current, weathering, and wind erosion. When these materials are broken into pieces, these will be carried though water, air or glaciers. Sediments, when accumulate and harden form a layer. That’s why when you see a mountainous rock, you can observe sediments forming different layers. These sediments were then soft deposits but due to pressing together of the materials, the deposits hardened to form rocks.
Sediments are usually deposited in the sea because these are carried by water current of river and waves. For over thousands of years in accumulation of these materials, thick deposits can be formed. Overlying sediments will cause the sediments underneath to be compacted. Over time, the sedimentary particles will form rocks in the sea and because of plate movements, these rocks can be uplifted in the land forming rocky mountains. Sedimentary layers in rocks are formed because of too much pressure from the sediments which are deposited from water flow, rain, ice, and wind.
When looking into the accumulated sediments, it seems that layers are formed. Once the sediments overlay each other, evaporation may also take place which loses the water in the sediments. The crystals will then form, which later turn into rocks. As sediment deposition continues to build up for thousands of years, different types of sediments are also formed. This is the reason why sediments form layers of different colors.
The older layers are already formed earlier. As the process continues, new rock layers will then form above these old layers. Sedimentary layers are important factors in telling the history of the Earth. They can contain fossils that give clues as to what kinds of plants and animals existed years ago. The lower layers will tell the history of the earth million of years ago while the upper layers are history of the earth in recent years.