The structure of the Earth
Magma is molten rock under the Earth’s surface. Lava is molten rock that escapes onto the Earth’s surface, for example from a volcanic eruption.
Some eruptions produce runny lava, while others produce thick lava that escapes violently. Geologists study volcanoes to try to predict future eruptions, and to gather information about the Earth’s structure. Volcanoes can be very destructive, but some people choose to live near them because volcanic soil is very fertile. It contains minerals needed by plants for healthy growth.
Igneous rocks are made when molten rock cools down and solidifies. The slower the molten rock cools, the larger the crystals become. For example, gabbro has larger crystals than basalt because the molten rock that formed gabbro cooled more slowly.
Different types of igneous rocks form lava (molten rock on the Earth’s surface):
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