Brown Bluff: geology and gulls

The geology of the Antarctic Peninsula continued to fascinate as we arrived at Brown Bluff. The bluff in question is a line of pancake rocks towering over a huge glacier to the east and a narrow rocky beach. It sits at the entrance to the Weddell Sea on the edge of the Tabarin Peninsula, just a few nautical miles from Esperanza.

Englacial volcanoes are a new area of study, being volcanoes which have erupted underneath a heavy ice sheet, sothe rocks cools very slowly and under continuing pressure. The process creates rocks made of a basaltic conglomerate (the brown stuff) in which lava crumbs are embedded, reminiscent of a currant bun. In other places, pillow lava has formed, rock full of bubbles extruded into contorted shapes. At Brown Bluff this catcher’s glove rises from the beach like a buried giant caught by the sunlight as he tried to dig his way free.

These landscapes have a lot to tell us about the historical record, including the thickness of icesheets. This might offer hints to life in Antarctica in previous epochs. Did eruption sites offer refuges of warmth when glaciation spread? Were the ice sheets thinner than we thought in the past? How did these sites promote biodiversity on the continent? There’s an excellent article about these questions by Prof John Smellie at Leicester University. Further afield, studying such areas might offer clues to life on other planets: if we can find microbes that tolerated the water in such conditions here, might we also find them on Mars

The beach was full of life, though emptier than it would have been a few weeks earlier. The Adelie penguins had gone though the moulting gentoos still posed for us. The area is home to an important breeding colony of kelp gulls, well fledged by mid-March but their untidy nests are still sitting on the sides of the pillow lave boulders. Fur seals gamboled about. Most exciting of all, a leopard seal lay on a floe out on the water, basking in the sunshine in a break from hunting.

We climbed to the bluff and then came down a steep hill on the other side to walk beside the glacier back down to meet the zodiacs. It’s a huge glacier sweeping down from the interior, with penguins stalking across it from the high wall where it meets the sea. Of course some of our photographers marched out to meet them.

I was delighted to have the opportunity to see the moraine border of a glacier at close hand because one of my characters in a novel has an important fight in such an environment. I have lots of photos, uninteresting to anyone else, of the way the basalt mud pushes through the edge of the ice but is still treacherous underfoot. I was super-excited to visit the place, hence quite so many pictures.

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