by DAVID R. MONTGOMERY
He Brought the Flood: Guru Rimpoche watches over a Bhutan village IMAGE/Design Pics/Keith Levit
I came to Tibet in the spring of 2002 to investigate a geologic mystery: How had the mighty Tsangpo River cut through the rising Himalaya to carve the deepest gorge in the world? Origin questions like this one fascinate me. I’m a geomorphologist—I study landforms and construct scientific narratives to explain the evolutionary processes that created and molded them. For years, I believed that my stories stood apart from myth in that they were forged in the topography of real landscapes—in the shape of hills to the lay of valleys. But that was before I visited the Tsangpo.
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Similarly, inhabitants of the Arctic and high alpine regions, like the Tibetans of the Tsangpo valley, have retained flood myths that seem to describe glacial dam breaks. Norse mythology, for example, recounts how Odin, the “allfather” of gods, and his brothers killed the ice giant Ymir, whose blood, made of water, gushed forth in a deluge that drowned men and animals. Connecting this fantastical tale to an historical act is fraught with speculation. But I’d be surprised if Ymir wasn’t born out of an actual ice-dam rupture as glaciers retreated from Scandinavia at the end of the Pleistocene.
A third category of flood stories reflects the experiences of river communities, who speak of perpetual rains and slowly rising waters. The biblical story of Noah, from the Book of Genesis, is the iconic example. This Hebrew myth has roots in an older Mesopotamian tale recorded, in blocky cuneiform runes, on a fragmented clay tablet excavated from the ruins of an ancient library. The inscription portrays a righteous man who receives a divine warning of an impending flood intended to destroy humanity. He is ordered to build a vessel—an ark—and bring his family and animals aboard to ride out the storm.
There may be geological truth behind this tale, too. It’s possible, for instance, that heavy rains swelled the Tigris and Euphrates rivers enough to breach their levees, filling the lowlands like a bathtub. Columbia University oceanographers Bill Ryan and Walter Pitman came up with another hypothesis in the early 1990s. Analyzing sediment cores from the bed of the Black Sea, they discovered that before 5600 B.C., the sea was a large freshwater lake. Then, when glacial ice melting off the poles raised sea levels worldwide, the Mediterranean overtopped a narrow strip of land and decanted into the lake. The inflow “roared and surged at full spate for at least three hundred days,” the researchers write in their book Noah’s Flood, cascading over the land at 200 times the flow of Niagara Falls.
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