Ecology
It only takes a couple of hundred years for the world's largest volcanoes to form and start erupting, scientists said. Such “super volcanoes” were thought to have existed for at least 200,000 years before they start spitting molten rock onto the lake surface, but it has recently been revealed that this is happening much faster.
Scientists took rock samples in the area of the ancient super volcano of the Long Valley Valley in California. The results of their research made it clear that the lava of the magmatic basin under the top of this volcano began to come to the surface several hundred years after its formation. This volcano erupted about 760,000 years ago and covered about half of North America with a layer of ash.
Such super eruptions could eject hundreds of cubic kilometers of ash—hundreds of times more than any other eruption in human history.
Eruptions of this magnitude could release enough ash to have an impact on climate around the world for years to come. According to one theory, the eruption near present-day Lake Toba in Indonesia 70,000 years ago had a long-term effect and almost destroyed all of humanity.
Scientists were able to get at least some information about these super volcanoes, mainly by studying crystals of a material called zircon, which contains small amounts of radioactive elements. The age of these elements can be determined using the same techniques used to determine the age of archaeological artifacts and dinosaur bones.
Modern studies of zircon suggest that the time period between the formation of huge magma pools and subsequent eruptions can range from several hundred to several thousand years.
Scientists at Vanderbilt University have presented several pieces of evidence by collecting samples from the Long Valley. They assumed that the volcano's basin formed just 500 years before the eruption.
Initially, magma pools consist only of liquid rock with a small amount of crystallized minerals.
Over time, the number of crystals increases, but this process stops when erupting. As a result, the timing of these crystals' formation may provide clues as to how long the magma pool existed before the eruption.
Researchers paid more attention not to zircon, but to ordinary quartz crystals. Due to the fact that the processes and timing of quartz formation in the unusual conditions of the magma pool underground are well known, the team of researchers was able to determine how long it took crystals from the Long Valley super volcano to form before the eruption begins.
Scientists estimate that quartz was formed between 500 and 3,000 years.
“Our research showed that when these huge magma basins formed, it didn't take too long before the eruption began,” the scientists said. “The fact that the process of magma formation took place within a historical period of time, and not a geological one, completely changes the situation.”
Scientists believe that currently none of the planet's known giant magma pools are about to erupt. Scientists plan to explore these questions further to understand how basins develop and be able to predict super eruptions.