A keystone in a changing world - Antarctica: Global Science from a Frozen Continent - page 42

Figure 2.10 Map of Lake Vostok, the largest subglacial

lake lying in a rift in the Gamburtsev Mountains. (Credit:
Michael Studinger)

A sleeping giant

Unlike the other continents, Antarctica has low
seismic activity and very few active volcanoes. It
was originally thought that the thick ice sheets
may have masked any earthquake activity but we
now know it is a characteristic feature of
Antarctica, with the exception of the northern
portion of the Antarctic Peninsula. As far as we
know, the Antarctic continent is not crossed by or
close to any plate boundaries, which is where we
expect to find volcanic and earthquake activity.

Antarctica sits in the middle of a large plate - the

surrounded by constructive
[growing], diverging plate boundaries beneath the
Southern Ocean. This means that earthquakes and
volcanic activity occur well away from the
Antarctic continent and that the plate is growing
at its edges, moving away from neighbouring
plates with new basaltic rock being added to the
leading edge of the plate. This contrasts with the
northern tip of the Antarctic Peninsula where a
series of small tectonic plates are caught up
between the big Antarctic and Southern American
plates. One small plate, the Drake Plate, is
currently sinking very slowly (with associated
seismic activity) and being destroyed beneath the
South Shetland Islands, a process known as subduction. The Drake Plate is the last
remaining part of what was once a much larger plate that was subducting beneath
the western margin of the whole Antarctic Peninsula. With the exception of
steaming fumaroles on Bridgeman Island, there is no volcanic activity on the South
Shetland Islands associated with the subducting Drake Plate. However, a marine
basin forming the current seaway of Brans

Antarctic Plate -

eld Strait, opened a few million years ago
between the South Shetland Islands and the Antarctic Peninsula, with Deception
Island situated on

the spreading ridge, in some ways analogous to Iceland sitting on the Mid-Atlantic

- one of the two currently most active volcanoes in Antarctica -