Krakatau History of Krakatau A long time ago

Krakatau

History of Krakatau A long time ago Krakatau was one large island. Eruptions divided the island, splitting Krakatau into 3 parts in the form of a ring, called a caldera. The 3 islands are called Rakata, Sertung, and Panjang. The volcano started erupting again, building the main island, Rakata, in the center of the caldera. In May 1883 Rakata began erupting again. There were small eruptions all summer, until August 26 when the eruptions started getting worse. Then one big explosion caused 2/3 of the island to collapse, or sink into the ocean on August 27, 1883.

The Caldera Volcano 2/3 of Krakatau was destroyed in the 1883 eruption. This happened because as the magma chamber emptied the outer walls failed and collapsed. This is also what happened in the eruption long ago. When the walls collapsed they created tsunamis, which killed 36, 000 people on Java and Sumatra.

Location • Krakatau is located in southwestern Indonesia. • It is in the Sunda Strait, between the islands of Java and Sumatra. • Krakatau’s coordinates are 16. 1 S and 105. 4 E

Krakatau Island • This is a picture of the island now. • The dotted line is an outline of what the island looked like before August 26, 1883.

Before & After

Why Here? Krakatau is just 1 of the volcanoes in the Sunda Strait. The Sunda Strait is where the Australian plate and the Eurasian plate meet. Here the Australian plate is subducted under the Eurasian plate and as it descends the rock melts. Volcanoes are created where the magma rises through the crust. The volcano line running down the Sunda Strait (Java and Sumatra) changes abruptly at Krakatau. This is because the subduction of the crust is faster along the Sumatra trench than along the Java trench. It marks a major tectonic break and Krakatau marks a focal point in the bigger tectonic picture.

Pictures

Eruptions The biggest explosion of Krakatau occurred on August 26 and 27, 1883. Before the eruption the island was about 18 sq. miles. After the eruption the island was only 6 sq. miles. The eruption caused an earthquake which created tsunamis that reached more than 115 feet high and traveled some 8000 miles. The waves killed about 36, 000 people on the nearby islands of Java and Sumatra, and destroyed 295 costal towns. The explosions produced some of the loudest noises in history.

Other Eruptions • Before Krakatau’s 1883 eruption, the only previous recorded eruption of Krakatau was in 1680. • Krakatau was dormant after 1883, until 1927. • In 1928, 22, 358 earth tremors were registered on volcanic observatory on Panjang. • A fourth island emerged in August 1930. By fall 1932 the island was 47 meters high and 700 meters in diameter. • In November 1992, Krakatau erupted for 4 days. 35, 650 sq. meters were covered by lava that was about 5 meters thick.

More Pictures

Statistics • • Krakatau is about 300 meters high. Krakatau diameter is between 3 and 4 kilometers. Krakatau is a caldera volcano. Krakatau is an ejecta volcano which means it spews out ash and lava. • Krakatau’s eruptions are explosive. • Krakatau alternates between dormant and active. As of the mid 1990’s it was active. • Krakatau has a plinian eruption.

Information • Ash from the 1883 eruption was discharged 50 miles high, and encircled the Earth within 2 weeks. • The island is uninhabited.

Lava • Krakatau’s lava type is aa (pronounced ah-ah). It’s flow is usually thicker (about 3 -5 meters), rougher, and red. One major chemical in the lava is silica (silicon and oxygen).

Bibliography • Encarta Encyclopedia Deluxe 2000 • Volcano World http: //www. volcano. und. edu/ • Volcanoes of the World http: //www. vulcan. wr. usgs. gov/Volcanoes/ framework. html • PBS Wild Indonesia http: //www. pbs. org/wildindonesia/island/5. html