The first recorded volcanic eruption in Antarctica occurred on Bridgeman Island (South Shetland Islands) in early 1821, < 2 years after Antarctica was discovered. However, the observations were disputed owing to a lack of physical evidence. A consensus arose that they probably referred to Penguin Island, a young volcano with a well-formed volcanic cone situated just 60 km to the west. However, a recent re-examination of the historical reports demonstrated that the event was undoubtedly located at Bridgeman Island. Our new study demonstrates that the eruption was explosive and lasted throughout 1821. The vent was situated in the sea ~500 m to the west of Bridgeman Island and the eruption was hydrovolcanic (Surtseyan). The new volcano constructed a tuff ring composed of unconsolidated lapilli and ash, which rapidly coalesced with nearby Bridgeman Island, similar to how the Capelinhos volcano joined with neighbouring Faial (Azores) in 1957–1958. The tuff ring had a very low profile and was rapidly removed by marine erosion. However, fumarolic activity persisted for a few decades. Because the eruption is only 200 years old, the underlying volcanic construct (Bridgeman Rise) should be regarded as dormant rather than extinct.

King George Island (South Shetland Islands, Antarctic Peninsula) is renowned for its terrestrial palaeoenvironmental record, which includes evidence for potentially up to four Cenozoic glacial periods. An advantage of the glacigenic outcrops on the island is that they are associated with volcanic formations that can be isotopically dated. As a result of a new mapping and chronological study, it can now be shown that the published stratigraphy and ages of many geological units on eastern King George Island require major revision. The Polonez Glaciation is dated as c. 26.64 ± 1.43 Ma (Late Oligocene (Chattian Stage)) and includes the outcrops previously considered as evidence for an Eocene glacial ('Krakow Glaciation'). It was succeeded by two important volcanic episodes (Boy Point and Cinder Spur formations) formed during a relatively brief interval (< 2 Ma), which also erupted within the Oligocene Chattian Stage. The Melville Glaciation is dated as c. 21–22 Ma (probably 21.8 Ma; Early Miocene (Aquitanian Stage)), and the Legru Glaciation is probably ≤ c. 10 Ma (Late Miocene or younger). As a result of this study, the Polonez and Melville glaciations can now be correlated with increased confidence with the Oi2b and Mi1a isotope zones, respectively, and thus represent major glacial episodes.

New mapping and dating of volcanic outcrops on the east coast of Admiralty Bay, King George Island, has demonstrated that Eocene volcanic sequences are dominant and also crop out extensively elsewhere, particularly on the eastern part of the island. The sequences can be divided into at least three formations (Hennequin, Cape Vauréal and Carruthers Cliff) together with Eocene strata at Warkocz and near Lions Rump that are currently unassigned stratigraphically. New and recently published 40Ar/39Ar ages indicate that all of the formations are Early Eocene in age, mainly Ypresian, extending to Lutetian and possibly even Priabonian time in more easterly outcrops. Compositional contrasts exist between the groups (calc-alkaline vs tholeiitic). The formations are mainly composed of lavas, and many show evidence for contemporary inundation by water. They are interbedded with sedimentary rocks deposited mainly during flooding events as debris flows, debris avalanches, hyperconcentrated flows, from traction currents and in lakes. The common presence of juvenile volcanic detritus suggests that the sediments were probably linked to explosive hydrovolcanic eruptions, some of which were possibly rooted in summit ice caps. Other evidence is also permissive, but the presence of Eocene ice on King George Island is not well established at present.