Magma under the volcanoes is in the solid state.
An international team of geologists found that the magma under volcanoes mostly in the solid state and melted for several years before eruption.
In the study, researchers observed the content of lithium in zircons thrown out during the eruption of a volcano in the Taupo region (New Zealand). It turned out that the zircons is carried out at temperatures of about 650-750 degrees Celsius for several centuries, and the heating above the melting temperature of magma occurs only for a few decades before the eruption.
Geologists have analyzed seven samples of zircon ejected during the eruption in the region Tuapo about 700 years ago. These minerals are of igneous origin, they move along with the magma, the exchange of substance by diffusion. For radioisotope Dating, scientists have determined the age of minerals — about 50 thousand years.
According to the authors, zircon could not be at temperatures above 750 degrees Celsius for more than 40 years. Under these conditions, the magma melts. The temperature regime from 650 to 750 degrees could be maintained around the zircons no longer 150-1200 years, at this temperature, magma mushy and mostly composed of solid crystalline fragments. Scientists also emphasize that in 50 thousand years of its existence, samples of zircon, the system of volcanoes erupted repeatedly TAPO. However, apparently, the warming from other isogeny didn’t work on zircons.
The reason for the strong heating before the eruption remains unknown. Its presence indicates that magma eruption is at least a two stage process. The authors note that zircons describe the evolution of only one system — the region Tuapo. To show that such behavior is universal magma will require additional research.