Professor John Smellie tells us about his recent fieldwork to the two southernmost volcanoes in the world

Posted by lcb14 at Jan 13, 2016 11:50 AM |
Professor John Smellie has just returned from Antarctica, working with geologists of the United States Antarctic Programme and a British field assistant on the two southernmost volcanoes in the world. Known as Mt Early and Sheridan Bluff, the volcanoes are located at 87°S, at the head of the Scott Glacier just 300 km from South Pole on the edge of the desolate, featureless snow and ice expanse that is the high polar plateau.
Professor John Smellie tells us about his recent fieldwork to the two southernmost volcanoes in the world

John Smellie at Scott Glacier

The volcanoes have been visited only twice: at their discovery in the mid 1960’s and again briefly by geologists in the 1970’s, who suggested on minimal evidence that the volcanoes may have erupted under the East Antarctic Ice Sheet (EAIS) in early Miocene times (20 and 16 m.y. ago). Both outcrops are small and very remote, situated at 2500 m elevation and more than 1000 km from the nearest comparable volcanic rocks. Part of their importance lies in the fact that they are situated far inland and, to explain significant fluctuations in oxygen isotope values for the early Miocene oceans and provenance (clast source) variations in Antarctic shelf sediments, conflicting and currently unresolvable ideas have been postulated about the development of the Antarctic Ice Sheet during the Miocene, when the world was much warmer: in particular, was the EAIS much thicker than present at times and capable of overtopping the Transantarctic Mountains, an enormous mountain range 3000 km long that crosses Antarctica, separating East from West Antarctica? Visiting the outcrops became viable with the establishment of a United States temporary strategic field camp on the Shackleton Glacier this year. The Shackleton Glacier is one of several huge outlet glaciers (the Beardmore and Scott glaciers are others) that drain the EAIS through the Transantarctic Mountains into West Antarctica. The Shackleton camp is sited just 250 km from the two volcanoes, just an hour’s flying by fixed-wing aircraft

Scott Glacier field camp
Scott Glacier field camp

Our first close view of Mt Early; planning our attack
Our first close view of Mt Early; planning our attack

To take part in the project, I flew to New Zealand and transferred to an LC130 (Hercules) transport flight to McMurdo Station (USA) along with American petrologist Kurt Panter and Masters student Jenna Reindel. After a week gathering together the field unit (tents, skidoos, sledges and provisions), the three scientists together with field assistant Tim Burton were deployed to Shackleton Glacier. Half the party was rapidly established at Scott Glacier but the weather clamped down immediately, stranding them alone in their tent for two frustrating weeks before a weather window allowed the remainder (including myself) to join them. Thereafter we had several successive days of excellent weather – clear sunny days but with a freezing breeze. Because of the elevation and latitude, the temperatures were very low, minus 20°C and lower (not including wind chill), and we were all affected variably by the high elevation that made us breathless with every exertion. Despite this we managed to complete about 90 % of our tasks in short order and we retraced our route back to McMurdo by aircraft.

It will take many months to fully assess our results but, provisionally, it appears that one of the volcanoes was probably erupted subglacially beneath a substantially thicker palaeo-EAIS. By contrast, and surprisingly, the other volcano may not be glacial at all but might have erupted under much warmer climatic conditions in an ice-poor setting corresponding to an interglacial. Fully characterising the eruptive palaeo-environments will be challenging but that is what makes geology, and doing geology under the harsh Antarctic conditions in particular, so interesting.

A cold lunch stop at 2700 m on Mt Early
A cold lunch stop at 2700 m on Mt Early

John working at Sheridan Bluff, high above Scott Glacier
John working at Sheridan Bluff, high above Scott Glacier

Typical windy conditions on the outcrop making life difficult
Typical windy conditions on the outcrop making life difficult

The snow-drifted campsite after a blow
The snow-drifted campsite after a blow

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