The group is composed of the Fumarole Bay Formation consisting of hydrovolcanic tephra, the Basaltic Shield Formation consisting of lavas and Strombolian scoria, and the Outer Coast Tuff Formation consisting of lapilli-tuffs. The Port Foster Group's principal outcrops are located at South Point, Cathedral Crags near Entrance Point and north of Punta de la Descubierta forming spectacular coastal cliffs along the western portion of the island. : iii Stratigraphy of the island is characterized by the pre- caldera Port Foster Group and the post-caldera Mount Pond Group, both within the Deception Island Volcanic Complex. Volcanic tremors are common, originating from depths less than 10 km. Deception Island volcanic ash layers have been found on other South Shetland Islands, the Bransfield Strait, the Scotia Sea and in South Pole ice cores. The island is associated with Bransfield Basin seafloor spreading that includes a volcanic ridge and seamounts dating back to the Pleistocene. Landsat 8 satellite photograph taken on 23 March 2018ĭeception Island is the exposed portion of an active shield volcano 30 km in diameter. The history of volcanic eruptions is still under investigation, but several larger eruptions happened in the last 10,000 years.
Three of five population growth phases were terminated by a sudden crash, due to volcanic eruptions from the active volcano of Deception Island. Ī 2016 study on Ardley Island, 120 km (75 mi) to the northeast, examined lake guano sediments and studied penguin population dynamics over 7,000 years. The linear Costa Recta spanning most of the east coast is hypothesised to be a scarp of a retreated submarine fault.
Other features of the island include Mount Kirkwood, Fumarole Bay, Sewing-Machine Needles, Telefon Bay, and Telefon Ridge. Others form bays within the harbour, such as the 1 km (0.6 mi) wide Whalers Bay. Several maars line the inside rim of the caldera, with some containing crater lakes (including one named Crater Lake). Just inside Neptune's Bellows lies the cove Whalers Bay, which is bordered by a large black sand beach. Raven's Rock, a navigation hazard, lies 2.5 m (8.2 ft) below the water in the middle of the channel. The outer coast of the island is characterized by 30–70 m (98–230 ft) cliffs of rock or ice. The port is rimmed by a shallow coastal shelf with sandy- gravelly beaches. The port is a basin with a flat floor up to 170 m (560 ft) deep with several small submarine cones and domes. The bay has a narrow entrance, just 500 m (1,640 ft) wide, called Neptune's Bellows.
The centre of the island has been flooded by the sea to form a large bay, now called Port Foster, about 10 km (6.2 mi) long and 7 km (4.3 mi) wide. Over half (57%) of the island is covered by glaciers up to 10 m thick, ice-cored moraines, or ice covered pyroclasts. The highest peak, Mount Pond on the east side of the island, has an elevation of 539 m (1,768 ft), while Mount Kirkwood on the west has an elevation of 452 m (1,483 ft). Located within the Bransfield Strait, the island is roughly circular and horseshoe-shaped, with a maximum diameter around 15 km (9.3 mi). Looking WSW from the center of the caldera
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