Lava is the word for magma when it erupts onto the Earth's surface. Geologists also use the term to describe the solidified deposits of lava flows. Lava is from the Italian word for stream, which is derived from the verb lavare, to wash. The type of lava erupted by Nyiragongo and many volcanoes in the East Rift zone of Africa, called alkaline lava, has an extremely low viscosity, making it almost as fluid as water. Alkaline lava has a melting temperature in excess of 2,000 degrees Fahrenheit. The fluidity and extreme temperature of Nyiragongo's lava make for a particularly deadly combination during eruptions.