Calderas

Calderas are large volcanic depressions formed by collapse of the summit or flanks of a volcano into underlying chambers evacuated by very large explosive eruptions or the effusion of large volumes of lava flows. Earth's calderas range from a kilometer to as much as about 100 kilometers in width; many contain scenic caldera lakes. Calderas may be simple structures formed during an eruption that truncates either the summit of a single stratovolcano or a complex of multiple overlapping volcanoes, such as at Crater Lake in Oregon. Other calderas are compound structures formed incrementally as a result of multiple eruption-related collapses, such as the massive 30 x 100 km wide Toba caldera in Sumatra, which was formed during four powerful explosive eruptions during the Pleistocene. Calderas are most often defined as depressions produced as a result of large-scale eruptions, but the word has also been used as a morphological term that encompasses volcanic depressions formed by erosion or large volcanic landslides. Calderas may be ephemeral features that are partially or totally obscured by post-caldera eruptions.

Photo by Tom Casadevall, 1987 (U.S. Geological Survey)

Toba

The 35 x 100 km wide Toba caldera, partially filled by waters of Sumatra's Lake Toba, is Earth's largest Quaternary caldera. This view looks west toward the northern end of Samosir Island, which is part of a massive inclined block uplifted after eruption of the Young Toba Tuff (YTT) about 74,000 years ago. The island, once entirely covered by Lake Toba, is formed of caldera-fill deposits of YTT capped by lake sediments.

Photo courtesy Tom Casadevall, 1988 (U.S. Geological Survey).

Banda Api

The arcuate islands of Neira and Lonthor, seen here looking east from the summit of Indonesia's Banda Api volcano, are remnants of two largely submarine calderas that preceded the construction of the Banda Api stratovolcano. The outer caldera has a diameter of 7 km, the nested inner caldera is 3 km wide. Neira, the largest town in the Banda Islands, occupies the southern tip of Neira Island.

Photo by Chris Newhall, 1989 (U.S. Geological Survey).

Taal

A small, 3-km-wide caldera is located at the center of Volcano Island, in the Philippines' southern Luzon Island. The 5-km-wide Volcano Island lies within a much larger, 15 x 20 km Taal caldera, whose low, western wall is seen across Lake Taal in the distance. The small island in the center of the photo, a remnant of historical eruptions on Volcano Island, is a geographical oddity--an island in a lake on an island in a lake on an island.

Photo by Chris Newhall, 1991 (U.S. Geological Survey).

Pinatubo

The climactic eruptions on June 15, 1991, created a 2.5-km-wide caldera at the summit of Pinatubo volcano. The elevation of the caldera floor is more than 900 m below that of the pre-eruption summit of Pinatubo. Steam rises from fumaroles on the caldera floor in this October 4, 1991, view from the north. The outer flanks of the caldera are stripped of vegetation and covered with deposits of airfall ash and pyroclastic surges.

Photo by Lee Siebert, 1977 (Smithsonian Institution).

Mashu

Mashu is a 6-km-wide caldera on the northernmost Japanese island of Hokkaido. It truncates a stratovolcano constructed on the ESE rim of the larger Kutcharo caldera. Mashu caldera is seen here from its SW rim with the small island of Kamuishi, a mostly submerged lava dome, in the center of the lake. The steep-walled caldera is one of the scenic highlights of Hokkaido. The latest eruption of Mashu took place about 1000 years from Kamuinupuri, whose lower flanks appear at the extreme right.

Photo by Dan Miller, 1990 (U.S. Geological Survey).

Akademia Nauk

Akademia Nauk caldera in central Kamchatka, seen here from the slopes of Karymsky volcano looking SW, is one of two overlapping calderas formed during the late Pleistocene within the 15-km-wide Polovinka caldera. The snow-capped ridge at the upper left is the southern rim of Odnoboky caldera, whose northern rim is truncated by the Akademia Nauk caldera. Karymsky Lake fills the 3 x 5 km Akademia Nauk caldera, which had its first historical eruption in 1996.

Photo by Dave Wieprecht, 1995 (U.S. Geological Survey).

Crater Lake

The spectacular 8 x 10 km wide Crater Lake caldera was formed about 6850 years ago when Mount Mazama, a complex of overlapping shield volcanoes and stratovolcanoes, collapsed following a major explosive eruption. The eruption blanketed a huge area with ash falls and produced pyroclastic flows that swept all sides of the volcano. The caldera, seen here from its southern rim, is 1200 m deep and filled to half its depth by the intensely blue waters of Crater Lake.

Photo by Jaime Incer.

Masaya

A broad expanse of youthful lava flows extends across the floor of Nicaragua's Masaya caldera, whose wall forms the arcuate rim in the background. The lava flows originated from the post-caldera cones of Masaya and Nindirí and constrain Lake Masaya against the eastern caldera wall. Recent lava flows have flooded much of the caldera and have overflowed its rim in one location on the NE side. This view from the NW shows Mombacho volcano in the distance.