A keystone in a changing world - Antarctica: Global Science from a Frozen Continent - page 61

Figure 2.26 Mt Hampton, one of the many volcanic
cones in Marie Byrd Land. (Credit: John Smellie)

central vent volcanoes and 30 small
satellite volcanic centres formed in
Marie Byrd Land on the

flank of the
rift system, rising to elevations between
2 and 4000m above sea level. Most
of these impressive volcanoes are
covered in snow and their bases are
buried beneath the West Antarctic ice sheet. Mt Sidley is the tallest volcano in
Antarctica at 4181m high, rising 2200m above the surrounding ice level. Only
Mt Berlin is considered active, as it has a streaming fumarolic ice tower and an
underlying ice cave with elevated air temperatures. Although mostly inactive today
their characteristic volcanic pro le can still be seen through the ice. A second

volcanic flanks of

the rift system in the western Ross Sea region. Most volcanism occurred on or
along the front of the Transantarctic Mountains and includes the well known
large volcanic cones (Mt Melbourne, Mt Discovery, Mt Morning) mostly older than
5million years, and the three major volcanoes that coalesced to form Ross Island
(Mounts Terror, Bird and Erebus) building up over the past 5million years. Mt
Erebus remains as the most active volcano within this mostly extinct province,
although some ancient volcanoes within this province show evidence of geothermal
activity. Mt Melbourne has warm ground that steams near its summit, and an
ash layer exposed in ice on the volcano

field, the McMurdo volcanic province, formed on the opposite

flank that suggests it erupted less than
200 years ago. Fumaroles also occur on a recently recognised active volcano Mt
Rittmann.
The maximum topographic relief from the top of the

' s

flanking mountains to
the subglacial basins within the rift system is approximately 7 km. The thinned
and extended crust has subsided to allow thick sequences of sedimentary rocks
to accumulate in marine basins and record an amazing unique record of how
Antarctica has cooled from a 35million years ago with

greenhouse gases very much higher than today to an

' greenhouse world '

with its
thick ice sheets. Scientist have drilled through this sedimentary pile to depths of
over 1100m to sample the rocks that record the advance and retreat of the
Antarctic ice sheets through time. We have not yet sampled rocks that record
the greenhouse

' ice house world '

icehouse transition. This remains a key target that may enhance
our knowledge of the future climatic conditions that could result in the collapse
and ultimate disintegration of the Antarctic ice sheets.

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