| An international team of scientists
has found that the second largest volcanic eruption in human
history, the massive Bronze Age eruption of Thira in Greece,
was much larger and more widespread than previously believed.
During research expeditions in April and June, the scientists
from the University of Rhode Island and the Hellenic Center
for Marine Research found deposits of volcanic pumice and
ash 10 to 80 meters thick extending out 20 to 30 kilometers
in all directions from the Greek island of Santorini ... |
| "These deposits have changed our thinking
about the total volume of erupted material from the Minoan eruption,"
said URI volcanologist Haraldur Sigurdsson.
In 1991 Sigurdsson and his URI colleague Steven Carey had
estimated that 39 cubic kilometers of magma and rock had erupted
from the volcano around 1600 BC, based on fallout they observed
on land. The new evidence of the marine deposits resulted
in an upward adjustment in their estimate to about 60 cubic
kilometers. (The eruption of Mount Tambora in Indonesia in
1815 is the largest known volcanic eruption, with approximately
100 cubic kilometers of material ejected.)
An eruption of this size likely had far-reaching impacts
on the environment and civilizations in the region. The much-smaller
Krakatau eruption of 1883 in Indonesia created a 100 foot
high tsunami that killed 36,000 people, as well as pyroclastic
flows that traveled 40 kilometers across the surface of the
seas killing 1,000 people on nearby islands. The Thira eruption
would likely have generated an even larger tsunami and pyroclastic
flows that traveled much farther over the surface of the sea.
"Given what we know about Krakatau, the effects of the
Thira eruption would have been quite dramatic," said Carey,
a co-leader of this year’s expeditions. "The area
affected would have been very widespread, with much greater
impacts on the people living there than we had considered before."
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| Image courtesy of Haraldur Sigurdsson,
Steven Carey, Matina Alexandir and Katy Croff. |
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Thira has erupted numerous times over
the last 400,000 years, four of which were of such magnitude
that the island collapsed and craters were formed. Some scientists
believe the massive eruption 3,600 years ago was responsible
for the disappearance of the Minoan culture on nearby Crete.
Others link the eruption to the disappearance of the legendary
island of Atlantis.
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| Image courtesy of the Institute for
Exploration, the University of Rhode Island (URI) Graduate School
of Oceanography (GSO), and the URI Institute for Archaeological
Oceanography. |
While investigating the seafloor around Santorini, the scientists
explored the submarine crater of the Kolumbo volcano, just 7
kilometers from the island of Thira and part of the same volcanic
complex, and discovered an extensive field of previously unknown
hydrothermal vents. Using remotely operated vehicles from the
Institute for Exploration, the scientists recorded gases and
fluids flowing from the vents at temperatures as high as 220
degrees Centigrade.
"Most of the known vents around the world have been
found on the mid-ocean ridges in very deep water and in areas
where there are geologic plate separations," Sigurdsson
explained. "The Koloumbo and Santorini volcanoes are
in shallow water at plate convergences, the only place besides
Japan where high-temperature vents have been found in these
conditions."
"The high temperature of the vents tells us that the
volcano is alive and healthy and there is magma near the surface,"
added Carey.
The scientists said that, in addition to fluids and gases,
the vents are emitting large quantities of metals, including
silver, which precipitate out to form chimneys on the crater
floor up to 10 feet tall and 2 to 4 feet wide. The floor of
the crater is covered in a layer of red and orange mats of
bacteria 2 to 3 inches thick that live on the nutrients in
the vent fluids. Bacteria also cover the vent chimneys, and
4- to 5-inch long, hair-like bacterial filaments extend from
the chimneys making them "look like hairy beasts, like
woolly mammoths," according to Sigurdsson.
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