Ask A Scientist

Is Krakatoa a real island?

Asked by: Megan Hull
School: Maine-Endwell Middle School
Grade: 6
Teacher: Mr. Wagstaff
Hobbies/Interests: Hobbies: Dancing, singing, acting
Career Interest: Actor, singer

Answer from Richard Naslund

Professor of geology, Binghamton University

Research area: Volcanology, crystallization of magmas, ore deposits, chemistry of the Earth
PhD school: University of Oregon
Family: Married, with five children
Interests/hobbies: Travel to geologically interesting places, scuba diving and raising tropical fish, hiking in the woods
Web page address:

Krakatoa (or Krakatau in Indonesian) is a real place located in the Sunda Strait between Sumatra and Java.  The name is used to describe a small group of islands that are the remnants of a large volcano that has erupted violently several times in the past.  Its most recent big eruption occurred in 1883 and has been described as the largest modern eruption.  The 1815 eruption of Tambora in eastern Indonesia was several times bigger, but occurred before the invention of the telegraph, so the world didn't hear about it until months or years later.  The famous message, "Where once Mount Krakatoa stood, the sea now plays", was sent around the world within hours of its climactic eruption. 

The effects of the Krakatoa eruption were also felt worldwide, so people were able to link the cause and the effects as they happened.  The Sunda Strait is on the major shipping route between Europe and China, so the progress of the eruption was recorded in numerous ships logs. The eruption began in May and grew in strength over the next few months. In June and July sounds from the eruption could be heard in Batavia, the capital of the Dutch East Indies (now called Jakarta, Indonesia), 150 kilometers (95 miles) away from the volcano. 

On August 26th, the day before the big event, sounds from the volcano were so loud that they broke windows in Batavia.  No one can say that it erupted without warning.  On August 27th seawater leaked into the magma chamber, and the resulting explosion threw over 20 cubic kilometers (5 cubic miles) of volcanic ash and debris into the air.  The volcano collapse produced a huge depression in the ocean floor called a caldera, and a tsunami wave 40 meters (130 feet) high that killed over 36,000 people on nearby Sumatra and Java.  The sound of this final explosion was heard over 4800 kms (3000 miles) away.  The shock wave from the eruption traveled around the world seven times and was observed at every weather station on earth that had a barometer to record changes in air pressure. Volcanic ash thrown into the stratosphere produced intense red sunsets throughout the world for the next several years.  Artists in the 1820's and 1880's painted landscapes with beautiful red sunsets as a result of the Tambora and Krakatoa eruptions.  In fact, the sunsets were so intense that the fire departments in Poughkeepsie, NY and New Haven, CT rushed out at dusk one night in 1884 looking for the barn fires that they were sure must be burning somewhere nearby.  The volcanic ash and volcanic gases absorbed so much sunlight that the average temperature worldwide was lowered more than a degree Celsius (2 degrees Fahrenheit) over the next two years.   In 1927, a new volcano began to slowly build in the old Krakatoa caldera, and has now formed the island of Anak Krakatau, which in Indonesian means son-of-Krakatoa.  

Professor Richard Naslund is currently living in Santiago, Chile while on sabbatical leave from Binghamton University.  He and his family visited a number of active volcanoes during their Chilean summer vacation (January and February, 2010).


Last Updated: 3/1/17