[9] The flanks of this volcano feature ridges and domes, as well as traces of mass wasting such as chutes.

[10] The islands are surrounded by shallow shelves at 120–130 metres (390–430 ft) depth, which probably formed through erosion during glacial periods, when sea levels were lower.

[13] Where there are outcrops, all three islands appear to consist of layers of lava flows and scoria or pyroclastics.

[32] Elsewhere, the sea between the two islands only reaches depths of 55 metres (180 ft)[33] and the strait is no more than 6-kilometre (3.7 mi) wide,[34] its seafloor covered with sediment.

[40] The tholeiitic magmas form through the melting of pyrolite mantle triggered by the entry of water released from the subducted crust in about 80–100 kilometres (50–62 mi) depth.

[38] Mean temperatures in the South Sandwich Islands hover around freezing;[43] at Southern Thule they are estimated to range between −1 and −11 °C (30 and 12 °F).

[12] Winds blow mostly from south and northwest, and frequent extratropical cyclones and storms pass through the archipelago.

[55] The principal animals on the submarine slopes of Southern Thule are annelids, crustaceans, molluscs and nematodes.

[57] The submarine habitat may have been severely impacted by the formation of the Douglas Strait caldera and the eruption that caused it.

[58] Presently, frequent mass wasting regularly buries the submarine slopes, devastating faunal communities.

[13] The Bellingshausen fumaroles occur around the southern side of the crater and their vents have various shapes and sizes.

[61] In 1963, volcanic ash was observed overlying ice on the southwestern side of Thule, perhaps indicating a recent eruption.

[13] A similar observation was made with scoria on Thule Island the preceding year, when a secondary crater may have been active.

[62] There are no known eruptions at Cook Island[47] nor any recorded hydrothermal activity in Douglas Strait[31] or Resolution caldera.

[34] In 1954–1956, Argentina built a hut on Thule Island, at Hewison Point, and named it "Teniente Esquivel".