The largest eruption of the 20th century occurred in 1912, from June 6 to June 8, to form Novarupta. Rated a 6 on the volcanic explosivity index the 60 hour long eruption expelled 13 to 15 cubic kilometers (3.1 to 3.6 cu mi) of magma, 30 times as much as the 1980 eruption of Mount St. Helens. The erupted magma resulted in more than 17 cubic kilometers (4.1 cu mi) of air fall and approximately 11 cubic kilometers (2.6 cu mi) of ash-flow tuff Only the 1991 eruption of Mt. Pinatubo in the Philippines was of a similar magnitude during the 20th century, ejecting 11 cubic kilometers (2.6 cu mi) of tephra.At least two larger eruptions occurred in the 19th century: the 1815 eruption of Tambora (150 km3 (36.0 cu mi) of tephra) and the 1883 eruption of Indonesia's Krakatoa (20 km3 (4.8 cu mi) of tephra).
Eruption of such a large quantity of magma from underneath the Mount Katmai area resulted in the formation of a 2-kilometer (1.2 mi) wide funnel shaped vent and the collapse of the summit of Mount Katmai creating a 600-meter (2,000 ft) deep,3 by 4 km (1.9 by 2.5 mi) caldera.
The eruption ended with the extrusion of a lava dome that plugged the vent. The 295 feet (90 m) high and 1,180 feet (360 m) wide dome is what is now referred to as Novarupta.
a small view :(
