Snow-covered Moku`aweoweo Caldera atop Mauna Loa shield volcano
(Mauna Kea in background). The caldera is 3 x 5 km across, 183 m deep,
and is estimated to have collapsed between 600-750 years ago. Several
pit craters along the upper southwest rift zone of Mauna Loa
(lower right) also formed by collapse of the ground. For more
information about the world's largest volcano, see Mauna Loa Volcano
from the USGS Hawaiian Volcano Observatory.
Photograph by C. Neal on
June 4, 1990
Kaguyak volcano, Alaska.
This lake-filled caldera formed atop a former stratovolcano (note
remnant of upper part of older cone at right center). The caldera
formed about 1,100 years ago and is 2.5 km in diameter. The
prominent peninsula and small island consists of lava domes
erupted after the caldera formed.
Photograph by B. Yount on
April 11, 1984
Ugashik volcano, Alaska.
Aerial view, looking southwest, of Ugashik caldera. The caldera is
5 km in diameter and is partially filled by at least five lava domes
erupted after the caldera formed.
Photograph by D. Wieprecht on August
20, 1995
Crater Lake, Oregon.
Crater Lake partially fills an 8-10 km-wide caldera that formed when
the top of the Cascade volcano known as Mount Mazama collapsed during an
enormous explosive eruption about 7,700 years ago. The eruption expelled
about 50 km3 of magma. This cataclysmic event was
followed by a series of post-caldera eruptions until about
5,000 years ago. These smaller events erupted lava flows, a lava dome,
and tephra from vents on the caldera floor. Such activity built Wizard
Island (above) on the western caldera floor. A 1997 report
describes the various types of volcano and earthquake
hazards in the Crater Lake area, estimates the likelihood of future
events, suggests ways to reduce risk, and includes a map of hazard
zones.