What Makes a Volcano

Deep below the ground, the Earth is very hot. In some places, melted rock called magma collects in large pools. When pressure builds up, this magma can burst through the surface. We call this a volcano. During an eruption, magma rises and pours out as lava. Lava is so hot that it glows red and orange. It flows down the sides of the mountain and slowly cools into hard, black rock. Ash and gas also shoot high into the sky. Volcanoes can be dangerous, but they are also useful. Over many years, the rock and ash break down and make the soil rich. Farmers near old volcanoes often grow healthy crops. Some volcanoes have been quiet for hundreds of years. Others erupt again and again. Scientists watch them closely, hoping to warn people before the next big eruption.