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April
26, 2007 Scientists examining
a spike in worldwide ocean temperatures
55 million years ago have linked it to massive volcanic eruptions that
pushed
Greenland and northwest Europe apart to create the Writing in the
journal Science,
geologists at "That prehistoric
volcanic activity released more than
2000 gigatonnes (billion metric tons) of carbon into the oceans and
atmosphere
in the form of methane and carbon dioxide – two potent
greenhouse gases,"
said Michael Storey of The scientists have
used precise dating techniques to match
a layer of volcanic ash that covers ocean floor sediments of that era
with a
layer in East Greenland and the Faeroes Islands (north of Scotland),
where the
ash overlies sequences of basaltic lava. These lavas, which form a
layered
sequence up to seven kilometers thick, are relics of massive flows from
the
mid-Atlantic ridge and other fissures along which North America and "Scientists have
known of this major prehistoric global
warming episode, called the Paleocene-Eocene thermal maximum, or PETM,
for some
time," said Carl Swisher, professor of geological sciences at To establish common
ages of the PETM-era marine ash layer
and the rock formations, the scientists measured the amounts of argon
gas
trapped in volcanic minerals. That dating method, performed in labs at
the
three universities, renders precise ages in geological time frames,
based on
known decay rates of potassium to argon trapped in the volcanic
material.
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