Sunday, August 26, 2007

About Krakatoa

Why is this interesting?

Because on August 26 - 27, 1883, this island volcano errupted with a stunning explosive energy that rocked the world.

Here are some of the highlights:
  • The sound of Krakatoa's destruction is believed to be the loudest sound in recorded history.

  • The cataclysmic explosion was distinctly heard as far away as Perth in Australia approx. 1,930 miles (3,110 km), and the island of Rodrigues near Mauritius approx. 3,000 miles (5,000 km).

  • According to official records, 165 villages and towns were destroyed and 132 seriously damaged

  • The official death toll recorded by the Dutch authorities was 36,417, mostly from the tsunamis which followed the explosion.

  • Nine tsunamis were generated, some of the tsunami waves are believed to have been over 100 ft (30 meters) high in places.

  • Those giant waves devastated everything in their path and hurled ashore coral blocks weighing as much as 600 tons.

  • Around noon on August 27, a rain of hot ash fell around Ketimbang in Sumatra. Around a thousand people were killed, the only large number of victims killed by Krakatoa itself, and not the waves or after-effects.

  • Darkness covered the Sunda Straits from 11 a.m. on the 27th until dawn the next day.

  • Every recording barograph in the world ducumented the passage of the airwave created by the explosion, some as many as 7 times as the wave bounced back and forth between the eruption site and its antipodes for 5 days after the explosion.

  • Blue and green suns were observed as fine ash and aerosol, erupted perhaps 50 km into the stratosphere, circled the equator in 13 days.

  • Three months later, the eruption fallout had spread to higher latitudes causing such vivid red sunset afterglows that fire engines were called out in New York, Poughkeepsie, and New Haven to quench the apparent conflagration. Unusual sunsets continued for 3 years.

  • The volcanic dust veil that created such spectacular atmospheric effects also acted as a solar radiation filter, lowering global temperatures as much as 1.2 degree C in the year after the eruption. Temperatures did not return to normal until 1888.

Before the eruptions it looked like this:

After the eruptions, it looked a lot like this:

The Aftermath:

When the first researchers reached the islands in May, 1884, the only living thing they found was a spider in a crevice on the south side of Rakata. Life quickly recolonized the islands, however. The eastern side of the island has been extensively vegetated by trees and shrubs, presumably brought there as seeds washed up by ocean currents or carried in birds' droppings.

Krakatoa Today:

In June 1927 a new island volcano, named Anak Krakatau ("Child of Krakatoa"), broke water. Initially, the eruptions were of pumice and ash, and it was quickly eroded away by the sea; but eventually produced lava flows faster than the waves could erode them. Here is is in 1992, erupting again.

The island is still active, with its most recent eruptive episode having begun in 1994. Since then, quiet periods of a few days have alternated with almost continuous eruptions, with occasional much larger explosions.

Since the 1950s, the island has grown at an average rate of five inches (13 cm) per week. Reports in 2005 indicated that activity at Anak Krakatau was increasing, with fresh lava flows adding to the island's area.