Half Moon Island
Early this morning, after an easy crossing of the infamous Drake Passage and way ahead of schedule, we reached the South Shetland Island chain and entered English Strait. This narrow opening between Greenwich and Robert islands allowed us to safely transit the line of islands and find a protected anchorage away from the waves, but not out of the wind, at a beautiful little island known as Half Moon. This delightful island gets its name from being shaped like a crescent moon, which was formed long ago by glacial action that left a curving terminal moraine consisting of boulders, shingles, gravel, and sand stretching between two impressive outcrops of basalt. The South Shetland archipelago is actually an island arc that developed within the last several million years by a series of volcanic eruptions. For the most part, these volcanoes are no longer active. Erosion by glaciations and freeze/thaw effects have created some remarkable rock formations, some of which are now covered by spectacular displays of colorful lichens (see Figure A).
Being small (only a couple miles or so in length) has precluded the development of an ice cap on Half Moon, unlike the larger islands that surround it. So, the penguins have chosen it for a secure breeding site, since they can find bare rocks on which to nest. We encountered three species of penguins on the island…the so-called brush-tailed penguins. Gentoo penguins first greeted us on the landing beach, but we soon encountered dense breeding colonies of chinstrap penguins a little higher up the slopes. Those of us who walked to the eastern end of the island also found a single Adélie penguin that had come ashore here to undergo its annual molt. In fact, many of the penguins, both adults and juveniles, were in their molting stage. This indicated to us that the breeding cycle would soon be coming to an end and everyone would probably abandon the island in the next few weeks.
We also encountered numerous Antarctic fur seals that have decided to use the island as a convenient hauling out site, again because of the lack of an ice cover. And, like most of the penguins here, these amazing animals feed exclusively upon krill. Antarctic fur seals provide one of the truly remarkable conservation stories of the world. The species was virtually extirpated by 19th century sealers who desired their valuable skins for the fur and felt trade. From only a relatively few animals that managed to evade the slaughter (perhaps one to two hundred individuals), the population has now rebounded to more than four million animals, most of which breed on South Georgia.
Half Moon Island is also interesting from a historic point of view, because we found evidence of past human activity along the shorelines. Near the landing site was a very picturesque broken-down, clinker-built wooden boat that probably dates back to the days of the whalers that utilized this protected bay. In the early 20th century, whalers towed the bodies of dead whales here in order to strip off their blubber layers and render the fat into valuable oil. The carcasses were then abandoned to sink in the surrounding waters. Some of the bones have since been washed back ashore, including a very impressive lower jaw from a blue whale (see Figure B). There is once again a human presence here at an Argentine base called Estacion Camara. During the Austral Summer, several scientists and support personnel inhabit the research station and study meteorology and marine biology in the area.
From here, we headed southward and made our way across the Bransfield Strait to the Antarctic Peninsula, where we plan to spend the next several days. In the late afternoon, during a heavy snowfall we came upon a huge iceberg with a large group of penguins perched on a low extension of ice just above the waterline. It obviously originated as a giant tabular berg, but had broken up into a much smaller and more irregular structure that must now be properly termed an iceberg. Seeing it suddenly appear ahead of us (we knew it was there long before we saw it, because of our radar) out of the mist and snow brought to mind how dangerous these things must have been to the sailing ships of old. It was very exciting to circumnavigate the iceberg twice, before getting back on our southerly track.
