Students, please read carefully through the information, watch the video, and answer the questions that follow (there are two posts). Bring your questions to class on Monday. If you have any questions ask them in the form of a comment and I will get back to you. Thank you and have fun!
The Hawaiian Islands are made up of large shield volcanoes that rise up out of the ocean. There is a geological 'hotspot' beneath the earth's crust that is currently underneath the Big Island. A hotspot is an area in the middle of a tectonic plate where volcanism occurs. Volcanism occurs in these areas because magma is under pressure and is able to push its way to the surface. Hot spots develop because of a weak or thin area in the plate.The force of the magma creates cracks in the earth's crust and these cracks get larger and larger as the magma wells up and creates a bulge. The force of the magma pushing up will eventually break through the cracks. When this happens runny lava oozes out and spreads around. The lava hardens when it comes into contact with the ocean water because the water is cold. This process happens over and over, thousands of times slowly building up more and more layers of magma until a large shield volcano is formed. First the volcano will form an undersea mountain but when the volcano reaches the surface of the ocean it creates a new island.
The Hawaiian Islands form a chain. This is because our earth's surface is made up of large tectonic plates that shift very slowly over time. The Hawaiian Islands are near the centre of the Pacific plate which slowly moving in a northwestern direction. Over millions of years this plate moves across the hot spot causing the original volcano to become extinct and creating a new volcano. As the older islands that are now extinct move away from the hot spot they no longer have volcanism and begin to erode. Kauai is the oldest of the islands and formed abut 5 million years ago and Oahu is the next oldest, both no longer have active volcanoes.
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