There followed nearly 60 years of little exploration,
although whaling ships continued to work the region
through the 19th century. Exploration
resumed with a vengence in 1895, with the next two
decades known as the "heroic age" in Antarctica.
Additional exploration between the World
Wars, during the 1957-58 International Geophysical Year,
and since the signing of the Antarctic Treaty in 1961
has contributed greatly to
understanding this vast region, but it is clear
that its historical record of volcanism is both short and very incomplete.
The Antarctic plate,
largely aseismic and immobile,
is broken internally by large rift structures
which have produced one of the
world's largest alkalic volcanic provinces.
The 3,200-kilometer-long West Antarctic rift system
is comparable in size to the better-known East
African rift. Volcanic constructs range from large
basaltic shields
to small
monogenetic vents;
the presence of the
continental icesheet
has resulted in a larger volume of hyaloclastite rocks than
perhaps any other subaerial volcanic region. The only subduction-related
volcanoes within or adjacent to the Antarctic plate form the
South Sandwich and South Shetland Islands.
Despite its size, Antactica ranks below all other regions
in number of dated eruptions, and only the
Pacific and Atlantic Ocean regions have
fewer historically active volcanoes.
It's historical record is brief, and 75 percent
of its eruptions are from this century.
Precise dating of past eruptions is
difficult -- much of the landscape is glacier-covered,
travel is daunting, and the wood needed for radiocarbon
dating does not grow in this extreme
climate -- and the region has the highest proportion
of volcanoes with uncertain status.
[Map,20K,InlineGIF]
