Geology Reference
In-Depth Information
god Odin and his brothers killed the frozen king, his blood (water) gushed forth to drown
the other ice giants. In one story, Odin and his siblings used the frigid giant's eyebrows to
make a wall separating the land of ice from the land of people. This boundary sounds sus-
piciously like the snaking ridges of glacial debris (called moraines) left by ice retreating
across Sweden and Finland. Viking songs and stories written down and preserved in Ice-
land before 1250
AD
also tell of how the modern world began when Odin and his brothers
slew an ice giant, releasing a great flood that inundated the lowlands and drowned large
mammals.
Flood stories from tropical climates have different narrative details. Accounts of big
floods from throughout the Pacific Islands describe rapid inundation as a huge wave from
the sea tears up trees and forces survivors to high ground. Many South Pacific flood stories
fail to mention rain at all. Instead, in these accounts, the sea rose to flood all but the highest
places. The remarkable tsunami stories from Sumatra, Borneo, New Guinea, Fiji, Tahiti,
Tonga, New Zealand, and Hawaii show how tales of infrequent local disasters can become
the stuff of legends.
Tsunamis come out of the blue, from over the horizon—sometimes from across an entire
ocean. When a big shock like a landslide or an earthquake displaces a lot of water, the pres-
sure wave travels. The surrounding ocean water doesn't. Moving at tremendous speed, the
resulting wave can cross an ocean in a few hours. Typically, the leading part of the wave
arrives as a water-level depression when it grounds out as it approaches shore. So the water
rushes out and then surges back in as the crest of the wave arrives. All too often, the ini-
tial mystery of the falling tide and the seductive exposure of bare seabed attract the curious
before a surging wall of water sweeps away everyone in its path. With no local cause to
invoke, divine displeasure might seem like the only reasonable way to explain monstrous
rogue waves. Fijians are said to have only recently stopped keeping great canoes ready in
case of a surprise flood from the sea.
The Indian Ocean tsunami resulting from the December 26, 2004, magnitude 9.3 earth-
quake killed more than a quarter-million people. Hard hit by the tsunami, Simeulue Island
in Indonesia's Aceh province lost only seven people out of a population of almost eighty
thousand. What explains such a low casualty rate? The islanders had an oral history re-
counting another massive tsunami that struck in 1907, killing three-quarters of the island's
