Geology Reference
In-Depth Information
flourish;thecoevolutionofthegeosphereandbiospherewillquicklyreturntoitspreindus-
trial equilibrium.
Megavolcano: The Next Hundred Thousand Years
The sudden catastrophe of an asteroid impact may pale beside the time-released death of
a megavolcano or flood basalt. Accompanying all of Earth's five greatest mass extinction
intervals—including the one contemporaneous with a big rock falling from the sky—was
globe-altering volcanism.
This is not to be confused with run-of-the-mill volcanic death and destruction in its vari-
ous forms. These include dramatic lava flows like those so familiar to Hawaiian islanders
livingontheslopesofKilauea—utterly destructivetoanydwellingsintheirpaths,butalso
localized, predictable, and easily avoided. Somewhat more deadly in this league of ordin-
ary volcanism are the explosions and ash falls of pyroclastic volcanoes, which can release
immense quantities of incandescent, steam-driven ash that race down a mountainside at
more than a hundred miles per hour, incinerating and burying everything in their path. Cue
the 1980explosion ofMountSt.Helens inWashington State andthe June1991eruption of
Mount Pinatubo in the Philippines, both of which would have killed thousands of people
if prior warnings hadn't prompted mass evacuations. Still more ominous is a third type of
volcanism as usual: the ejection of large quantities of fine-grained ash and toxic gases into
the high atmosphere.
The Icelandic ash eruptions of Eyjafjallajökull in April 2010 and Grímsvötn in May
2011 were relatively puny, releasing much less than a cubic mile of debris. Nevertheless,
they disrupted European air travel for several days and caused health concerns for many
people in nearby regions. The eruption of Laki in June 1783—among the largest historic
eruptions—releasedanestimatedfivecubicmilesofbasaltandassociatedashandgas,suf-
ficient to induce a long-lasting poisonous haze over Europe. A quarter of Iceland's pop-
ulation died, some rapidly from exposure to acidic volcanic gases and many more from
starvation during the subsequent winter. The disaster also affected lands more than a thou-
sand miles to the southeast, as tens of thousands Europeans, most in the British Isles, also
died from Laki's prolonged effects. Even more people died following the August 1883 ex-
plosion of Krakatoa and the resultant tsunami that swept nearby coastlines of Java and
Sumatra. And the colossal April 1815 eruption of Tambora, which produced an amazing
twelve cubic miles of lava, was the deadliest of all. More than seventy thousand lives were
lost, most as a consequence of agricultural failure and subsequent mass starvation. Tam-
bora's injection of immense quantities of sun-blocking sulfur compounds into the upper
atmosphere turned 1816 into the Northern Hemisphere's “year without a summer.”
