[ad_1]
When the sea level drops, the volcano of Santorini is about to rumble.
Santorini is an island volcano in Greece. It consists of a ring of islands around the central point of the volcano. The whole volcano was once above the water. But it collapsed after a violent eruption some 3,600 years ago. This eruption could have inspired the legend of the submerged city of Atlantis.
The researchers wanted to better understand what causes this volcano to explode. So they compared its past activity with historical sea levels. And when the sea level drops 40 meters (131 feet) below its current level, Santorini has an eruption crisis. The volcano remains calm when the sea level is higher. The team shared their findings on August 2 in Geosciences of nature.
Sea level is likely also affecting other volcanoes, the researchers say. This is because most volcanoes are in or near the oceans.
“It’s hard to see why a coastal or island volcano wouldn’t be affected by sea level,” says Iain Stewart. He is a geoscientist who did not participate in the study. He works at the Royal Scientific Society of Jordan in Amman. Taking sea level into account could make eruption forecasts more accurate, according to the authors of the article.
Simulate Santorini
Christopher Satow led the new study. He is a physical geographer at the University of Oxford Brookes. It’s in England. The Satow team first created a computer model from the volcano. This simulation included the magma chamber that powers the eruptions of Santorini. It lies about four kilometers (2.5 miles) below the surface of the volcano.
In the simulation, the crust above the magma chamber cracked when the sea level fell. (Lower sea level meant less water was pressing on the crust to hold it together.) The crust began to break when the sea level fell 40 meters below its current level.
“This gives the opportunity for the magma stored under the volcano to rise through these fractures,” explains Satow. It took about 13,000 years for the magma to reach the surface and cause eruptions. When the sea level rose again, it took about 11,000 years for the cracks to close and the eruptions to end.
Real world eruptions
The Satow team wanted to know if the computer simulates what happens in real life. Rock layers on the islands of Santorini contain clues about past eruptions. The seabed sediments contain evidence of past sea level. The team compared the volcano’s eruption history to these sea level records. These data go back 360,000 years.
Santorini has had 211 well-dated eruptions during this period. Sea level was low when much of Earth’s water was frozen in glacier during ice ages. All but three of the eruptions occurred during periods of low sea level. This meets the expectations of the computer model.
Santorini is now expected to enter a period of calm. The last time the sea level was 40 meters below today’s level was about 11,000 years ago. And the sea level is continues to increase due to climate change. Thus, the cracks in the crust above the Santorini magma chamber should close.
But a future violent eruption is not impossible. After all, a few of Santorini’s eruptions still occurred in the midst of high sea level.
Other volcanoes
The effect of sea level on Santorini is “really intriguing,” says Emilie Hooft. She is a geophysicist at the University of Oregon at Eugene. She isn’t totally surprised by what Satow’s group has found. “Other studies have shown that volcanoes are sensitive to changes in their stress,” she says.
For example, after superimposing glacier melted, Iceland’s volcanoes showed a slight increase in eruptions. The reason is similar to why the lower sea level wakes up Santorini. The retreat of a glacier will reduce the weight above the earth’s crust on Icelandic volcanoes. This allows more underground magma to rise to the surface.
Sea level is likely affecting volcanoes around the world, according to Satow. But what he does will likely vary. “Some will be very sensitive to changes in sea level,” he says. “For others, there will be almost no impact.” Rashes depend on many factors. One is the depth of the magma chamber that feeds a volcano. Another is the quality of the crust above this chamber.
But if sea level impacts a volcano in or near the ocean, “you would expect all of these volcanoes to be in sync,” says Satow. “Which would be amazing.”
[ad_2]
Source link