Hekla (Icelandic pronunciation: [ˈhɛʰkla]), or Hecla, is a stratovolcano in the south of Iceland with a height of 1,491 metres (4,892 ft). Hekla is one of Iceland's most active volcanoes; over 20 eruptions have occurred in and around the volcano since 874. During the Middle Ages, Europeans called the volcano the ""Gateway to Hell"".Hekla is part of a volcanic ridge, 40 kilometres (25 mi) long. The most active part of this ridge, a fissure about 5.5 km (3.4 mi) long named Heklugjá, is considered to be the volcano Hekla proper. Hekla looks rather like an overturned boat, with its keel being a series of craters, two of which are generally the most active.The volcano's frequent large eruptions have covered much of Iceland with tephra and these layers can be used to date eruptions of Iceland's other volcanos. 10% of the tephra created in Iceland in the last thousand years has come from Hekla, amounting to 5 km3. The volcano has produced one of the largest volumes of lava of any in the world in the last millennium, around 8 km3.