Krakatau, Sundra strait

Krakatau, Sundra strait

Krakatau volcano lies in the Sunda strait between the islands of Java and Sumatra. In about 416 A.D., caldera collapse destroyed the volcano and formed a 4-mile (7-km) wide caldera. The islands of Krakatau, Verlaten, and Lang are remnants of this volcano. The eruption and collapse of the caldera in 1883 produced one of the largest explosions on Earth in recorded time (VEI=6) and destroyed much of Krakatau island, leaving only a remnant. Since 1927, small eruptions have been frequent and have constructed a new island, Anak Krakatau (Child of Krakatau). Image courtesy of the Landsat Pathfinder Project.

In January of 1960 a group of scientist visited Anak Krakatau to record its renewed activity and to measure changes in the size and shape of the island. They observed explosive eruptions of pyroclasts from ash to boulders in size. This photograph shows a column of ash rising above the island. Rakata, a remnant of the volcano prior to the 1883 eruption, is in the background.

In 1960, Anak Krakatau had a minimum diameter of about one mile (1.5 km) and was 545 feet (166 m) tall. A crater on the south side of the island was 2,000 feet (600 m) in diameter and contain a growing cinder cone 300 feet (100 m) in diameter and 150 feet (50 m) high. The new cinder cone formed in about a month and can be seen just below the ash column. Verlaten Island, near the top of this photo, is a remnant of the volcano that was destroyed by the 416 A.D. caldera collapse.

Explosive, Vulcanian-type eruptions occurred at 1/2- to 10-minute intervals. The largest explosions produced turbulent clouds of ash and lapilli that rose 4,000 feet (1,200 m) above the vent. In this photo a column of ash is rising about 1,500 feet (450 m) above the crater. This episode of activity, which began in December of 1959, ended in 1963. Anak Krakatau has had at least nine episodes of activity since 1963, most lasting less than one year. The most recent episode began in March of 1994 and has continued to at least March of 1995 (last reported observation). Activity is similar to the 1959-1963 eruption.

All photographs courtesy of and copyrighted by Robert Decker.

Click here for recent photos from Krakatau.

Sources of Information:

Volcanoes of the World by Tom Simkin and Lee Siebert

Krakatau, Bulletin of the Global Volcanism Network, 1995, Bulletin of Volcanology, v. 20, no. 3. Results of the 1960 Expedition to Krakatau by Robert Decker and Djajadi Hadikusumo, 1961, Journal of Geophysical Research, v. 66, no. 10, p. 3497-3511.

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