What Is Geothermal Energy? At the center of Earth—about 4,000 miles (6,400 kilometers)below the surface—is a very hot core. Some scientists estimate its temperature at about 7600º Fahrenheit (4200º Celsius). Thecenter of the core is solid. The heat from this part of the core is powerful enough to melt rock into a hot liquid called magma. This molten (melted) rock forms the outer core. The heat from magma rises through Earth’s mantle. The mantle is the layer that surrounds the core. Geothermal energy powers volcanoes, geysers, and natural hot springs. Erupting volcanoes are probably the most famous geothermal events. When a volcano erupts, magma from underground shoots through Earth’s crust and fl ows into its surface as lava. Over time, people have learned to use geothermal energy to heat homes and produce electricity. Today, geothermal energy is more important than ever.