This is a picture of a geologist examining the eruptive hsitory of a volcano.
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Image from: U.S. Geological Survey, photo by Robert McGimsey
This is a picture of a geologist examining the lava flows of a volcano.
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When magma is erupted onto the surface in the form of lava, it becomes silicate rock. With each different eruption of the volcano, lava which comes to the surface is made of slightly different chemicals,...more
Ash is formed as a volcano erupts when rocks made by the volcano blow apart into millions of tiny pieces. The rocks are still very hot, because they just formed from lava. If the hot rocks come into contact...more
Cinder cones are simple volcanoes which have a cone shape and are not very big. Compare the size of this volcano to the strato-volcano in this image. They are usually made of piles of lava, not ash. During...more
Lava can move in two ways, wide flat lava flows, or through channels which squeeze the lava into a small area. The fastest lava flows move at about 6 mi/hr, an easy jog, but they average between 2/3 and...more
Plates at our planet’s surface move because heat in the Earth’s core causes molten rock in the mantle layer to flow. We used to think the Earth’s plates just surfed on top of the moving mantle, but now...more
Many kinds of surface features are clues to a sliding lithosphere. Two types of features can form when plates move apart. At ocean ridges, the crust splits apart to make room for molten mantle rock. Continental...more
As the Earth cools, hot material from the deep interior rises to the surface. Hot material is red in this drawing, under an ocean shown in blue green. The hotter material raises the nearby layers, and...more