a volcano devastates north america -- 1/22/16

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Today's selection -- from The Horse by Wendy Williams. 12 million years ago, the Brunei-Jarbridge volcanic eruption devastated North America. The corpses of many of animals that died in that eruption were preserved by the debris and can be studied today:

"On the day of the North American disaster, which occurred about 12 million years ago, horses of several different species were grazing a grass-covered plain in what's now Nebraska. Perhaps a few of the horses sheltered themselves from the sun under the walnut and hack­berry trees that then dotted the landscape. Perhaps a few nibbled at leaves on shrubs. But most were probably busy eating the grasses that had replaced the Eocene wetlands. Accompanying the horses were hump-free camels, saber-toothed deer, strange rhinoceroses, several spe­cies of dogs, elegant cranes, and long-tailed secretary birds.

"While the horses grazed, a thousand miles to the northwest a super­volcano exploded. ... The Bruneau-Jarbidge eruption was deadly. Its ash spread across hundreds of thousands of square miles, including the plain where the horses grazed. Tiny bub­bles of silica -- like soap bubbles but much, much smaller -- emerged from the volcano and then shattered, creating a multitude of glassy, curved microscopic shards that wafted, like parachutes, a thousand miles distant on the winds that blew to the east. When they finally landed on the grass, the horses and other grazers breathed these shards into their lungs while they ate. Imagine taking several glass Christmas tree ornaments and pulverizing them with a hammer, then spreading those sharp-edged infinitesimals out over a field of grass. That's what the animals inadvertently ingested.

Ash Fossil Beds

"Paleontologists have worked out the order in which the animals died. First, tiny birds fell out of the sky. Their lungs were the smallest and the most easily damaged. Then the smaller land animals succumbed. Then slowly, the larger animals, including the horses, died, their lungs destroyed by the glass-like micron-size silica that entered with every inhalation. The last to die were the largest animals with the largest lungs, the rhinos.

"It was a slow, agonizing death. It must have hurt the horses to breathe, but of course they had no choice. In their misery, many of the animals sought out a local water hole, no more than a slight indenta­tion in the plain that filled when the rains came. There wouldn't have been a lot of water, but apparently even this tiny oasis offered some kind of solace. Perhaps the horses wanted to drink, or perhaps they were just seeking wet mud to cool their terrible fevers. Their slow suf­focation caused bone decay, lung damage, swelling of body organs­ -- damage that's still visible even today on the many skeletons that have been left in situ for visitors to see.

"After they died, the prairie wind continued to blow. The light ash covering the plain drifted over the cadavers, entombing them. ... The animals were preserved in three dimensions, similar to Vesuvius victims. The same tiny glass shards that killed the animals also preserved them."