On a 2005 Antarctica expedition, we visited several places along, on or near the Antarctic Peninsula. Deception Island is an O-shaped island with a notch in it that lets ships enter its Port Foster. It is actually a large volcano caldera. We landed at Telefon Bay, the site of a 1970 eruption, for a hike up to some views of craters.

Mark Wasson, http://www.markwasson.com > Trips has detailed summaries of my trips