Wednesday, January 13, 2016

Farewell to Antarctica - Tabular Icebergs in Antarctic Sound, Brown Bluff Volcano, and Elephant Island

It's gone by quickly but the two trips to Antarctica are now complete (still to come however, is South Georgia Island and the Falklands - I do not leave the ship until January 21). To finish up the second trip we sailed to the northern tip of the Antarctic Peninsula and entered the Antarctic Sound. A surprise was waiting for us here.

Large tabular icebergs were spotted as we entered the Sound.

They looked as it they might be from the same mold as they were a similar size in the water.

These are massive pieces of ice that have flowed off of the Peninsula over very subdued terrain. Thus, they do not crack with tightly spaced crevasse. Crevasse spacing is what determines the size of icebergs.

I was on Deck 12 when I took these shots and that is about 100 feet off of the water. We could not see the tops of the bergs so I estimate that the height of the ice cliff is about 120 feet.

The larger mass of the bergs is below the waterline - maybe only 1/7th to 1/9th of the mass is above the water.

They are very cold and dense pieces of ice so they fracture quite regularly.

There were a parade of these tabular bergs, maybe 100 in all.

One iceberg has cracked into smaller pieces and then rotated in the water to find a new center of gravity.

No wonder the Antarctic Sound is called "Iceberg Alley." We came within 30 miles of seeing BK15. BK1 broke off of the Ross Ice Shelf (On the far side of Antarctica) in 2002 and then fragmented further to create the BK-series of bergs. BK15 was caught up in the western drift and went 3.4's of the way around the whole continent to arrive in the Weddell Sea. We were quite close but had to turn north.

After a morning cruising in Iceberg Alley on the ship, we then headed to a landing at Brown Bluff.

Brown Bluff at the northern tip of the Peninsula. This is an unusual volcano.

Above is my visual interpretation of what I could learn about the Brown Bluff volcano (after perusing I. P. Skilling. 1994). It is a Pleistocene-age cone about one million years old. Its morphology easily betrays its origin!

Rocks at Brown Bluff suggest it was erupted beneath a glacier, making it a sub-glacial volcano.

The hot lava melted the underside of the ice cap, forming a sub-glacial lake. The next deposits were water laid.

The landing at Brown Bluff.

Our ship framed by an iceberg.

A Southwest-looking landscape awaited us. This is a Pleistocene (1 million years old) volcano.

This is the unusual type of basalt called palagonite that betrays the volcano's origin.

These boulders rolled down from the high cliffs to land on the beach. Wind has given them these odd shapes.

I was happy to be stationed at these beautiful boulders and talk about them.

Pretty good-sized chicks on this nest.

Columnar basalt island offshore of Brown Bluff. This concludes my Antarctic season down here. I'm sure looking forward to next week when I return home. But first, Elephant Island, South Georgia and the Falklands!

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