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Sian Proctor's picture

Hello everyone, Beaches are fun to visit no matter where you are in the world, including the Arctic. So I hit the Barrow beach with oceanographer Dr. Kathleen Fischer to see what we could learn. Barrow's beach is very different from the tan colored, sandy beaches I am use to back home. The beach here is mostly gravel. Grains of sediment are classified based on there size, shape, and sorting. The smallest size is clay which are particles smaller than 1/256 mm. As you move up in size, the sediment changes to silt which is smaller than 1/16th mm but larger than clay, then comes sand which ranges in size between 1/16th mm and 2 mm, and gravel which is larger than 2 mm. 

As we explored the beach, I noticed other sediment characteristics such as shape. This gravel is well rounded and indicates that this material is on the move. Sediment becomes smaller and more rounded the further it travels from its original source. Now compare it to this shape. Notice how the rock shape is more angular. It hasn't traveled enough to smooth out these sharp edges. Beaches are well known for moving material. The incoming waves push and pull the sediment up and down the beach. Bad weather brings more energy with each crashing wave and this increases the erosion and deposition to the point where the shape of the coastline can be completely different after a really bad storm.

When sediment is all the same size we classify it as being well sorted. When the sizes vary from mud to gravel then it is considered poorly sorted. We saw areas where the gravel was well-sorted and other areas where it was poorly sorted. Take a look at this image - notice how the sediment changes from gravel sized to smaller and smaller pieces as you go up. Then repeats again. This is called graded bedding and indicates a change in the energy level as this material was being deposited. You can do this experiment at home. Take a jar and fill it with a mix of mud, sand, and gravel. Add some water, and then shake it up. Set it aside to allow the mixture to settle. When you come back - look at the layers. Take note of what is on the bottom, middle, and top. Tell me about your results in the comments below.

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