Sedimentary Environments

To understand the idea around sedimentary environments one must understand how they are formed. First there must be erosion of the material. This generally happens by three different processes, physical, biological or chemical weathering. Physical weathering can be caused by fracturing. This fracturing is caused by freezing and thawing of the rocks. The rocks contract when frozen and expand when they heat up causing them to break apart. Mineral wedging can also happen. This is where minerals fill a void in rocks and cause expansion, causing the rocks to fracture and break apart. Biological weathering happens from biological activity like animals and humans weathering away rocks by going through there daily activities. Roots are another thing that can cause weathering. As roots grow they break down the substrate causing the production of sediment. Lastly there is chemical weathering. Dissolution is the first type of chemical weathering. This is the dissolving away of solid material. Another type is hydrolysis where the hydrogen molecule in water becomes charged and able to break rocks down faster.

Next there must be transport of the material through water, wind, or ice. Water is a major cause of deposition. Water, especially if moving very fast can cause even large boulders to be mover downstream. Glaciers are another way deposition can happen. Large glaciers pick up rocks and move them along until they fall out. They can be moved long distances as long as the glacier does not start to melt.

There are many different types of sedementary environments. The first is mountains. Here the rocks tend to me large and angualr shaped because they have not traveled far from the source rocks. Glaciers is another environment. Here the rocks tend to be fairly well-rounded but there is a great variety in rocks because the glacier moves almost anything in its path.  Another sedementary environment is streams and rivers. The faster the movement of the streams, the heavier the material it can carry. When you see a gentle slow moving river there tends to be small well rounded pebbles because the rocks have traveled so far from the source rocks. Deltas have very nutrient rich sediments because this is where alot of sediment is deposited before it reached the ocean. Lakes are another type of environment. Here you tend to see very fine sediments, mostly clay in suspension because of the stagnant slow moving water.

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