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

Eruption Layers

An examination of consecutive lava flows of a volcano reveals the chemical evolution of the magma in the chamber.


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Cool It! Game

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Magma Chamber

Magma consists of remelted material from Earth's crust and fresh material from the aesthenosphere, relatively near the Earth's surface. When magma is erupted onto the surface in the form of lava, it becomes...more

Volcanic Ash

Ash is made of millions of tiny fragments of rock and glass formed during a volcanic eruption. Volcanic ash particles are less than 2 mm in size and can be much smaller. Volcanic ash forms in several ways...more

Cinder Cones

Cinder cones are simple volcanoes which have a bowl-shaped crater at the summit and rarely rise more than a thousand feet above their surroundings. They usually are created of eruptions from a single vent,...more

Flowing Lava

Lava can move in broad flat lava flows, or it can move through constrictive channels or tubes. Lava flows have a large surface area so they tend to cool quickly and flow slowly. The fastest unconstricted...more

How Do Plates Move?

Earth’s center, or core, is very hot, about 9000 degrees F. This heat causes molten rock deep within the mantle layer to move. Warm material rises, cools, and eventually sinks down. As the cool material...more

Clues to Plate Movements

Many kinds of surface features provide evidence of a sliding lithosphere. When two plates move apart, rising material from the mantle pushes the lithosphere aside. Two types of features can form when...more

Mid-Ocean Spreading Ridge

As the Earth cools, hot material from the deep interior rises to the surface. Hot material is depicted in red in this drawing, under an ocean shown in blue green. The hotter material elevates the nearby...more

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