Exotic Lava Flows

On Earth, most lavas have silica contents in the range from 30 to 78 wt%, and they are erupted at temperatures between 800 and 1170°C (see Chapter 2). However, some lavas have compositions and eruption temperatures outside this range. These are the exotic lavas that we will describe in this chapter. One type of exotic high-temperature, low-viscosity lavas called komatiites were important at an early stage in the development of the Earth’s crust. Another group of exotic lavas are forming only on a volcano in northern Tanzania—Oldoinyo Lengai—at the present time. These fascinating lavas, termed carbonatites, are renowned for their very low eruption temperatures and viscosities. The first people to see these strange lavas understandably mistook them for mudflows, and the vents were considered to be boiling mud pools.