Magma and lava are the same substance in two different forms. Magma is molten rock that is found beneath the earth's crust, while lava is what magma becomes once it reaches the surface and erupts from a volcano or crack in the earth.
Magma can also contain many other components besides just molten rock, including gases and crystals. This mixture maintains a temperature between 1,600 and 2,400 degrees Fahrenheit. The molten rock often contains silicon, iron, carbon, aluminum, magnesium and different alkalis. Magma is heated by geothermal convection and pressure. Typically, it is found several kilometers beneath the earth's surface.
The composition of lava determines whether its flow is explosive, fast-moving or slow and highly viscous. Temperature plays a less significant role in the look and feel of the volcanic rock that forms once the lava cools down. Pumice is one igneous volcanic rock that is shaped by its composition and the type of eruption. As lava violently shoots into the atmosphere, it rapidly cools and decompresses, allowing air bubbles to permeate the rock, leaving a bubble-marked texture and a light weight. Obsidian, on the other hand, is a high-silica rock that forms from quick-cooling lava found on the ground in highly viscous flows.