But Mt. Erebus isn’t just a mountain. It is a volcano. A volcano is an opening in Earth’s surface. Melted rock called lava flows out of the opening. When this happens, it is called an eruption.
There are volcanoes all over the world. Some of them are very old. They do not erupt anymore. But many volcanoes still erupt. Mt. Erebus erupts almost every day!
Ross Island is a cold place. It is near Antarctica. This means that Mt. Erebus is covered by snow and ice all year long. But the inside of the volcano is very hot. Steam from the inside of the volcano comes out the sides through cracks in the rock. The steam makes the ice melt and forms caves made out of ice. When the hot steam moves into the cold air, it freezes into pillars. They look like icicles that point up into the sky!
At the top of the volcano is a lake. But this lake isn’t made of water. It’s made of lava! Sometimes, a big bubble of gas inside the volcano shoots a big chunk of lava out into the air.

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