Q:What is the name of the archipelago that represents the remnants of a long-extinct ring volcano rising from a seabed plateau?  Answer the above question based on the context below:  The islands are composed of Tertiary igneous formations of granites and gabbro, heavily weathered by the elements. The archipelago represents the remnants of a long-extinct ring volcano rising from a seabed plateau approximately 40 metres (130 ft) below sea level.At 670 hectares (1,700 acres) in extent, Hirta is the largest island in the group and comprises more than 78% of the land area of the archipelago. Next in size are Soay (English: "sheep island") at 99 hectares (240 acres) and Boreray ('the fortified isle'), which measures 86 hectares (210 acres). Soay is 0.5 kilometres (0.31 mi) north-west of Hirta, Boreray 6 kilometres (4 mi) to the northeast. Smaller islets and stacks in the group include Stac an Armin ('warrior's stack'), Stac Lee ('grey stack') and Stac Levenish ('stream' or 'torrent'). The island of Dùn ('fort'), which protects Village Bay from the prevailing southwesterly winds, was at one time joined to Hirta by a natural arch. MacLean (1972) suggests that the arch was broken when struck by a galleon fleeing the defeat of the Spanish Armada, but other sources, such as Mitchell (1992) and Fleming (2005), suggest that the arch was simply swept away by one of the many fierce storms that batter the islands every winter. The highest point in the archipelago, Conachair ('the beacon') at 430 metres (1,410 ft), is on Hirta, immediately north of the village. In the southeast is Oiseval ('east fell'), which reaches 290 metres (950 ft), and Mullach Mòr ('big hill summit') 361 metres (1,185 ft) is due west of Conachair. Ruival ('red fell') 137 metres (449 ft) and Mullach Bi ('pillar summit') 358 metres (1,175 ft) dominate the western cliffs. Boreray reaches 384 metres (1,260 ft) and Soay 378 metres (1,240 ft). The extraordinary Stac an Armin reaches 196 metres (643 ft), and Stac Lee, 172 metres (564 ft), making them the highest sea stacks in Britain. In modern times, St Kilda's only settlement was at Village Bay (Scottish Gaelic: Bàgh a' Bhaile or Loch Hiort) on Hirta. Gleann Mòr on the north coast of...
A:
St Kilda