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The Island That Exploded

Examining the Wildlife of Rakata After Krakatau Erupted

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A lithograph of the eruption of Krakatoa.

A lithograph of the eruption of Krakatoa.

Photo courtesy Wikipedia.
At 10:02 am on August 27, 1883, the equatorial island of Krakatau was violently and abruptly re-sculpted. Preceded by a series of earthquakes and recurrent volcanic activity, the August 27th eruption shattered the island with a force exceeding that of 100 megatons of TNT.

The resulting sound wave rumbled 4600 kilometers to Rodriguez Island in the Indian Ocean. A plume of debris—magma, rock, and ash—rocketed 5 kilometers into the sky, as 18 cubic kilometers of the island exploded upward. Ash fell to the ground 840 kilometers away in Singapore. A 40-meter wave scoured a path that destroyed the coral reefs and coastal towns in its path. A cloud of volcanic dust dissipated into the atmosphere, creating green sunrises and red sunsets, and lowering global temperatures as much as 1/2 degree centigrade for five years following the blast. A massive underwater crater and a sickle-shaped, barren remnant of land were all that remained after the eruption. The remaining island now bears the name Rakata—it seems there was not enough of Krakatau left to merit keeping its name.

On a human timescale, this event—having occurred more than a century ago—is historical, remembered primarily in geology textbooks and by volcanologists. But on a geological time scale, this eruption is recent, and its effects continue to shape and ripple through the area's wildlife. In the months and years that followed the eruption, wildlife returned to the island by surprising methods. Spiders released silken threads into the wind and took to the air, floating over miles of open water before falling down on their new island home. Scientists suspect that the monitor lizard and the reticulated python swam to the island. Bats and birds—brave enough to venture out from the safe forest cover of Java and Sumatra—flew to the island. Rafts of floating debris such as logs or branches, provided transport for larger animals: mammals, amphibians, and reptiles.

Once these animals arrived to Rakata, they entered a growing, dynamic environment. The new arrivals created and filled novel habitats, continually changing and reshaping the face of Rakata. Some creatures flourished and then became extinct without explanation. Others remained extant when conditions were far from ideal. Populations of some species have reached an equilibrium while other populations continue to grow or decrease.

Krakatau and Rakata offer much hope for the resiliency of ecological systems. If you were to visit Rakata today, after a mere century of recolonization—a quick flash in geological time—you would see an island teaming with life. By studying the pattern of recolonization, regrowth, and population dynamics on Rakata, we can extrapolate and apply this understanding to help manage the isolated wildlands carved out by human development.

Refs:

  • Wilson, E.O. The Diversity of Life. Harvard University Press. 29 October 2002. Pages 16-23.
  • Simkin T, Fiske R. 1983. Krakatau 1883: the volcanic eruption and its effects: Smithsonian Institution Press, Washington DC, 464 p.
  • Moore, P. (1999). Ecology: A shrike for mobility. Nature, 397(6714), 21-23. DOI: 10.1038/16148
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