Is Mt St Helens old?
Helens? The eruptive history of Mount St. Helens began about 40,000 years ago with dacitic volcanism, which continued intermittently until about 2,500 years ago.
How many years was Mt St Helens dormant before 1980?
100 years Prior to the 1980 eruption, Mt St Helens had lain dormant for over 100 years, displaying few signs of volcanic activity since its last eruptive episode in 1857. Nevertheless, the potential for large, destructive eruptions at Mt St Helens was well known.
What is the largest supervolcano on Earth?
Rising gradually to more than 4 km (2.5 mi) above sea level, Hawaiis Mauna Loa is the largest active volcano on our planet. Its submarine flanks descend to the sea floor an additional 5 km (3 mi), and the sea floor in turn is depressed by Mauna Loas great mass another 8 km (5 mi).