That’s the channel inside a volcano that opens up to the surface. As it cools it becomes a very hard type of igneous rock. This one first formed over 350 million years ago. Then, millions of ...

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Volcanic rock is formed when lava or magma cools down and becomes a solid. We call this type of rock igneous rock. Here are three different types of igneous rock from the Museum’s collection.

also influences the types of minerals and textures found in the resulting igneous rocks. Thundereggs specifically form in rhyolitic lava. Rhyolitic lava flows are volcanic flows composed of ...