Geology Research Paper

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Primary structures are structures used in Geology to help us identify which way is up of igneous and sedimentary rocks in the field. Most of these structures are found in sedimentary layers but some are found in igneous rocks. In sedimentary rocks we have mud cracks, ripple marks, flute casts, flame structures, graded bedding, crossbedding, animal tracks and worm burrows. Mud cracks are formed when an area of shallow water evaporates of leaving mud or clay behind. When this mud starts to dry, it shrinks and pulls apart causing the cracks. When we see them in layers of rocks we can tell by how the cracks are which way is up. Ripple marks are seen in various sediments and are formed from streams or shallow seas. When we see these we can tell…show more content…
The troughs are deeper where the current of the stream is stronger and they become shallower and wider as the current is weaker. These marks show which was is up in a stream. Flame structure form when the weight of the overlying rock layer force lower rock layers to push up through other layers. The upward movement of the structures show which way is up in the rock layers. There structures are not too common. Graded bedding is a great way to find which way is up. Graded bedding is the sorting of grain sizes of material. In a stream the movement of water helps to settle out larger material first and it gets smaller as you go up. This may get confused with a delta so you would have to make sure that there wasn’t a delta around your area of study. Animal tracks would have been left by small animals like worms and lizards that walked or crawled over a surface and left and imprint. By looking at the imprint you can tell where the animal walked and in turn which way is up in the rock. With the animals you can also find worm burrows. The burrows are traces of burrowing organisms and can be used to identify which way is up by looking at where the burros are in the rock

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