A few volcanoes like the Hawaiian Islands form from a hot spot, or a weak spot in earth’s crust, where magma forces its way to the surface. Most volcanoes occur at plate boundaries, where two plates are moving away (diverging) or together (converging). VOLCANOESĪ volcano is simply an area where magma, or molten rock, from the earth’s mantle reaches the earth’s surface, becoming lava. ![]() The movement of the tectonic plates also means that they are associated with much of the world’s volcanic and seismic activity. Fossil evidence from this time period confirms that Antarctica was connected to Australia and South America and much warmer than it is today. The continents eventually broke apart, merging again approximately 200 million years ago in the supercontinent Pangaea. Geological evidence from Antarctica supports the theory that North America and Antarctica were connected approximately one billion years ago in the global supercontinent Rodinia. These plates move in relation to each other, slowly changing the location of earth’s continents and oceans. Image courtesy of Wikimedia.Įarth’s lithosphere is broken into seven major and many minor tectonic plates. The fractured rock is thus incorporated into the glacier’s load and is carried along as the glacier slowly moves. As the water refreezes, the ice acts as a lever loosening the rock by lifting it. This water flows into cracks in the bedrock. The intense pressure at the base of the glacier causes some of the ice to melt, forming a thin layer of subglacial water. Plucking occurs as a glacier flows over bedrock, softening and lifting blocks of rock that are brought into the ice. Glaciers primarily erode through plucking and abrasion. In the Arctic and sub-Arctic, glacial erosion has shaped much of the landscape. Building terraces and planting trees can help reduce erosion. Excessive erosion leads to loss of soil, ecosystem damage, and a buildup of sediments in water sources. Deforestation, overgrazing, construction, and road building often expose soil and sediments and lead to increased erosion. Erosion is a natural process, though it is often increased by humans’ use of the land. However, weathering and erosion can happen simultaneously. Erosion is distinguished from weathering - the physical or chemical breakdown of the minerals in rock. ![]() Wind, water, and ice are the three agents of erosion, or the carrying away of rock, sediment, and soil.
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