A Dangerous Job

Joanne Green walks by a glowing river. This river has no water, however. Instead, it is made of hot liquid rock, or lava.

The lava river is extremely hot, and so are the rocks surrounding it. “If you aren’t careful,” she says, “you’ll melt your boots on the hot rock. Or worse!”

Green is used to these dangers. They are part of her job. She is a volcanologist, a scientist who studies volcanoes.

Green is studying Kilauea, a volcano in Hawaii. Green studies other volcanoes, too. Earth has thousands of them.

Volcanoes on Earth

Most people think that volcanoes are simply large mountains that pour out lava. But a volcano actually starts deep beneath Earth’s surface, or crust.

The layer of rock below the Earth’s crust is called the mantle. But the pressure and high temperature near the center of the Earth change the rock to liquid. The pressure can force the liquid rock upward. It moves up through cracks in the Earth’s crust. This can form a volcano.