An enormous volcanic eruption at the Greek Island of Santorini is thought to have brought about the collapse of one of the era’s great civilizations three and a half thousand years ago. New research has shown that the likelihood of this volcano blowing its top again may be shaped by the height of sea levels. This discovery could improve our capacity to predict eruptions on other volcanic islands – a matter of immense importance to those living nearby.
Today, Santorini is a small island popular with tourists – but 3,700 years ago it was part of a much larger island, then a center of the Minoan culture. Unfortunately for the Minoans, their island sat on an enormous volcano, and around 3,600 years ago it blew up. This left a string of small islands on the caldera rim and launched a tsunami that overthrew the heart of the Minoan culture in Crete.
The volcano had erupted many times before, although usually less explosively. In Nature Geoscience, researchers report that the cycles they have observed are driven by earlier sea levels.
Besides shaping history, the Minoan eruption exposed cliffs on the remaining islands that preserve a record of 211 past eruptions over the last 360,000 years.
“Comparing this eruption history to a sea level record allowed us to show for the first time that the sea level has had an important role in determining the timing of eruptions at Santorini, and probably at many other island volcanoes around the world,” lead researcher Dr Christopher Satow of Oxford Brookes University said in a statement.
“The mechanism is quite simple: falling sea levels remove mass from the Earth’s crust and the crust fractures as a result. These fractures allow magma to rise and feed eruptions at the surface.”
There is a long delay between fracturing and eruption, however. All but three of the 211 eruptions occurred 11,000 years after a time when sea levels were at least 40 meters (131 feet) below the current height
Santorini is now approaching a safe period due to the rising oceans at the end of the last ice age, so fears of a 2012 eruption may not be repeated often.
The effects of volcanoes on the climate are well known, inducing a short-term cooling as ash blocks the Sun, sometimes followed by longer-term warmer conditions driven by carbon dioxide release, Satow points out: “What is less well known is that on long timescales, the climate can also affect volcanoes.”
Melting of ice sheets at the end of the last glacial era added around 100 meters (328 feet) to sea levels, and the weight of all that water affected the fractures feeding the 57 percent of the world’s volcanoes located in or near the sea.
The influence of glacial changes on polar volcanoes, such as those in Iceland, have been studied for a while, but the idea that the loss of all that ice would have volcanic consequences elsewhere in the world is much newer.
Sea levels will be rising for the foreseeable future – certainly not falling by 40 meters. However, for other volcanic islands, the threshold height could be different, making upcoming changes decisive.