It lurked in the Indian Ocean for centuries, a virtually unknown volcanic island with a history of violent explosions. The island was Krakatoa.
Part of the Sunda volcanic arc, the island of Krakatoa rose in the ocean when there was a subduction of the Indian-Australian plate under the Eurasian plate. It heaved, and grumbled, deposited ash and eventually grew to a structure almost 2600' high. Then in 416A.D. it literally blew its top, and the whole island collapsed inwards, creating a sub-surface caldera, or depression in the land form, that was four miles wide.
Two new islands formed from portions sticking up out of the water. And after several centuries passed, more volcanoes began to surface, with three merging to form the new Krakatoa, bigger, and more dangerous than before.
May 20, 1883 Krakatoa belched smoke and ash and began a rumbling that would continue into August. As it turned out, the seismic activity was creating cracks in the magma chambers under the ocean's surface, and water leaking in was being turned to super heated steam.
On August 26, 1883, the first major explosion sent up a black cloud that was observed 120km away. Less than 24 hours later, August 27, 1883, three more explosions would follow on the heels of each other, all within the span of 4 1/2 hours. The last would be the most powerful, estimated at a force of 150 megatons of TNT. By comparison, the Hiroshima atomic bomb was only 20 kilotons.
Walls and windows shattered, 80 miles away. In the immediate region of Krakatoa, ships reported a layer of pumice three feet thick on the ocean's surface. Tsunami waves of over 40m high, decimated coastal centers. The explosions were heard more than 2,000 miles away in Australia, and ash was shot 50 miles up into the atmosphere where it caused almost total darkness in the vicinity, for two days. Thirteen days later, a belt of ash encircled the Earth, and would cause unusual effects for years to come.
And once more, Krakatoa sank into the sea, the main walls and above ocean forms, destroyed by the last explosion. Left behind, was a "minor" form, eventually discovered to be an active volcano itself. The locals named it Anak Krakatoa. Researchers estimate it is only a matter of time, until it follows the same explosive path as its predecessor.
