Krakatoa Erupts!

volcano

The island volcano of Krakatoa, an uninhabited volcanic island near Indonesia, erupted on this date in 1886. It was heard over 3,000 miles away and was one of the biggest natural disasters ever recorded. It expelled huge clouds of gas and ash, generated massive tsunamis nearly 120 feet tall, and killed more than 36,000 people, victims of the tsunamis that followed the collapse of the volcano into the caldera below sea level.

The island is about 3 miles wide and 5.5 miles long (9 by 5 kilometers).  Before the historic eruption, it had three linked volcanic peaks: Perboewatan, the northernmost and most active; Danan in the middle; and the largest, Rakata, forming the southern end of the island. Krakatoa and the two nearby islands, Lang and Verlatan, are remnants of a previous large eruption that left an undersea caldera between them.

It is thought that debris from the earlier eruptive activity in May of that year must have plugged the neck of the cone, allowing pressure to build in the magma chamber. The initial explosion ruptured the magma chamber and allowed seawater to contact the hot lava. The result is known as a phreatomagmatic event. The water flash-boiled, creating a cushion of superheated steam that carried the pyroclastic flows up to 25 miles (40 km) at speeds in excess of 62 mph (100 kph). The explosion is estimated to have had the explosive force of 200 megatons of TNT.

The explosions hurled an estimated 11 cubic miles (45 cubic km) of debris into the atmosphere, darkening skies up to 275 miles (442 km) from the volcano. In the immediate vicinity, dawn did not return for three days. Barographs around the globe documented that the shock waves in the atmosphere circled the planet at least seven times. Within 13 days, a layer of sulfur dioxide and other gases began to filter the amount of sunlight able to reach Earth. The atmospheric effects made for spectacular sunsets all over Europe and the United States. Average global temperatures were up to 1.2 degrees cooler for the next five years.

In 1927, some fishermen were startled as a column of steam and debris began spewing from the collapsed caldera. Krakatoa had awakened after 44 years of calm. Within weeks, the rim of a new cone appeared above sea level. Within a year, it grew into a small island, which was named Anak Krakatoa, or Child of Krakatoa. Anak Krakatoa has continued to erupt periodically, although mildly. (from Live Science)

 

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