The rocks that form from magma are crystalline and fit into a general category called igneous rocks. Examples of common types of igneous rock include granite and basalt.
One way to learn how different types of igneous rock form is to compare the relative sizes of their mineral crystals. Igneous rocks with larger mineral crystals (for example, granite) cool slowly below the surface. Basalt, with its fine mineral structure, cools relatively quickly after it erupts as lava from a volcano.
Image: 3D model of hot magma plumes (light orange) rising from the Earth's core (dark orange, centre), cooling, and sinking back down (credit: Shuxia Zhang/Shuo Wang/SPL)
How big is the magma chamber at Yellowstone?
Seismologists study how earthquake waves travel through the Earth to map the huge magma chamber below Yellowstone National Park.
Geophysicist Bernard Chouet explains what notes from an organ can tell us about volcanoes.
Geophysicist Bernard Chouet explains how notes from an organ and a volcano about to erupt give off similar resonant signals. As magma enters cracks below the Earth's surface, it resonates and gives off signals known as long period events. These signals help scientists predict eruptions.
Liz Bonnin uses a plum to explain what's happening inside the Earth.
Reporting from Eyjafjallajokull volcano in Iceland, Liz Bonnin explains the Earth's inner structure using a plum to show the different layers inside our planet. She explains why hot bits of the mantle that are rising melt to form magma.
Magma (from Greek μάγμα, "thick unguent") is a mixture of molten or semi-molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals, dissolved gas and sometimes gas bubbles. Magma often collects in magma chambers that may feed a volcano or solidify underground to form an intrusion. Magma is capable of intrusion into adjacent rocks (forming igneous dikes and sills), extrusion onto the surface as lava, and explosive ejection as tephra to form pyroclastic rock.