What kind of volcano is Krakatau

USGS volcano map

Krakatoa by NASA

USGS Krakatau map

Krakatoa by NASA
(Landsat 5 Thematic Mapper instrument on May 18, 1992, the satellite image was composed of images in red, green and blue wavelength ranges).

Anak Krakatau by NASA

All times in Central European Summer Time (CEST)

All times in Central European Summer Time (CEST)

Simon Winchester

The Krakatau Volcano National Park is located between the two large Indonesian islands of Java and Sumatra. In the 4th century there was only a single volcano on this site, but in 416 the volcano's caldera collapsed. The remains formed a new caldera with a diameter of about 7 kilometers and the three islands of Verlaten, Lang and Krakatau. According to today's knowledge, the volcano was mainly active around the years 850, 950, 1050, 1150, 1350, 1550 and 1680-81. A possible strong eruption in 535 is still being discussed among scientists.
After a long period of rest, Krakatau erupted in August 1883 with such force that the explosion could still be heard in Madagascar and Alice Springs, Australia, thousands of kilometers away. Two thirds of the island were destroyed; of the three volcanoes on the island only Rakata existed after the explosion, of the other two volcanoes Danan and Perbuwatan practically nothing remained. A total of around 20 cubic kilometers of rock was hurled into the atmosphere. It was one of the heaviest explosions ever recorded on earth. During the eruption, the collapse of the caldera triggered a huge tidal wave: the tsunami reached heights of 30 meters on numerous coastlines, in individual bays up to about 130 feet, corresponding to about 40 meters. The number of dead is estimated at around 36,000 and the tidal waves penetrated some islands up to 10 kilometers inland. Even after the eruption of 1883, the volcano did not remain calm: Since 1927, persistent eruptions with repeatedly extracted material have formed the fourth island of the "Anak Krakatau" national park - the "child of Krakatau".

The Anak Krakatau was particularly active in 1960, when explosions occurred at intervals between half a minute and about 10 minutes. The main activity lasted from December 1959 to 1963. Ashes and rocks were sometimes thrown up to around 1,200 meters high into the sky. From 1963 to the present day, more than a dozen other phases of activity followed, most of which lasted less than a year. The island grew from year to year, and now it protrudes more than 400 meters out of the sea. In November 2007 and November 2010 new eruptions of the Anak Krakatau followed.

In the massive explosion in 1883 the island was almost completely sterilized and all life was wiped out. This gave scientists the opportunity to study in detail how such an isolated ecosystem recovered, how new species were added and maintained. The unique location of the islands in the Sunda Strait between the Indian Ocean and the Pacific offered the best conditions for this. Even the tropical rainforest recaptured the islands. Dense forests cover the slopes of Rakata, the remains of Krakatau after the explosion in 1883. Exactly 70 years later, another explosion in 1953 wiped out all life on the small island of Anak Krakatau and scientists were able to observe the same process again. Wind and water carried the first spores and animals soon followed. However, each of the four islands developed differently with different species, although they are only a few kilometers apart.

News about the volcano:
Anak Krakatau spits lava and gas (Spiegel, 11/08/07)
Eruption with lava, gas and rockfall (Welt, 11.11.07)
Indonesia's Krakatau roars and dazzles with fireworks (Reuters, 11/11/07)
Krakatau`s ash reaches Cilegon and Serang (Antara, 03.11.10)
Krakatau, Indonesia - volcanic earthquakes are creating unrest in coastal villages (Earthquake Report, 06.10.11)
Anak Krakatau: Giant blocks of rock litter ocean floor (BBC, December 15, 2019)

Reports on the eruption and tsunami on December 23, 2018:
When Anak Krakatau erupted between the islands of Sumatra and Java, there was a landslide that triggered a 3 to 10 meter high tsunami. Around 400 people were killed and many houses were destroyed.
Tsunami kills more than 200 people (n-tv, 23.12.18)
Tsunami struck without warning (n-tv, 23.12.18)
Tsunami triggered by Krakatoa eruption kills 222 people (ABC Australia, 23.12.18)
Much more deaths than initially assumed (n-tv, December 24, 2018)
At least 373 dead after the tsunami in Indonesia (Spiegel Online, 12/24/2018)
Indonesian tsunami likely caused by 'flank collapse' on Anak Krakatau (ABC Australia, 25.12.18)
Indonesian rescuers continue survivor search as tsunami death toll reaches 429 (ABC Australia, 25.12.18)
Heavy rain makes rescue work difficult after tsunami (n-tv, 25.12.18)
Authorities expand search for tsunami victims (Spiegel Online, 25.12.18)
Video shows ash clouds over Anak Krakatau (FAZ, 25.12.18)
Tsunami victims fear new giant wave (n-tv, 26.12.18)
Indonesia reroutes all flights around erupting Anak Krakatau (ABC Australia, 27.12.18)
Volcano shrinks by more than 200 meters (n-tv, 12/29/18)
Volcano shrinks by 228 meters (Spiegel Online, 29.12.18)
Krakatau lost two thirds of its height (Spektrum, 01/02/19)
Formerly a crater, now a water basin (Spiegel Online, 07.01.19)
Volcanic eruption triggered tsunamis 150 meters high (Spektrum, 06.12.19)

Some links to the volcano (German):
Apocalypse from below (ZDF)
The child of Krakatau (ZDF)
A volcano changes the world (ZDF)
Krakatau - a volcano explodes (Achim Hennings)
Krakatau - Minutes of a Disaster (3SAT)

Further links to the volcano:
Directorate of Volcanology and Geol. Hazard Mit.
Volcanoes in Indonesia
KRAKATAU, Sunda Strait
Krakatau Monitoring Online
The Great Explosion of the Krakatau Volcano (Dr. George P.C.)
The Great Tsunami of August 26, 1883 (Dr. George P.C.)
Krakatau by Volcano World
Indonesia Volcanoes and Volcanics (USGS)
1883 Eruption of Krakatau (USGS)
Krakatoa by Global Volcanism Program
Krakatau by Bob Jensen
Krakatau by John Seach
Krakatau Research Program by Dr Robert J. Whittaker
Anak Krakatau: Birth of an Island by Rob Whittaker
Krakatau by William Hutton
University of San Diego

Climatic effects:
The effects of the massive eruption in 1883 were not only enormous for the region in Southeast Asia. At higher altitudes, the ash spread across the entire northern hemisphere, which resulted in climatic changes in the period that followed. A total of around 20 to 21 cubic kilometers of ash were emitted, of which almost 10 percent of the finer dust reached heights of 27 kilometers and more. This dust circled the earth several times and not only caused spectacular sunsets in the northern hemisphere. After the outbreak, solar radiation was reduced considerably and the following year was around 1.2 degrees colder globally than the long-term average. It took years for conditions in the atmosphere to return to normal.

Latest news:
Messages from Yahoo (German)

Satellite images:
Anak Krakatau (NASA, 06/30/05)
Krakatau, Indonesia (NASA, 11/23/10)
Activity at Krakatau (NASA, 09/25/18)
Violent Puffs from Krakatau (NASA, 04/15/20)

Simon Winchester: Krakatoa. The day the world broke up: August 27, 1883, Albrecht Knaus Verlag, Munich 2003, 368 pages, ISBN 3813502244, 23.90 euros (see picture on the left) - reading sample