Published by the American Geological Institute
Newsmagazine of the Earth Sciences
into planetary past
On Jan. 18, 2000, a meteorite blazed through the night sky and landed
on the frozen surface of Tagish Lake near the Yukon-British Columbia border
in Canada. One week later, several fragments were removed from the icy
lake. Analyses have revealed the meteorite, now called the Tagish Lake
meteorite, is a new type of carbonaceous chondrite that also appears to
be the least altered meteorite ever found on Earth.
Undersea explorer Robert Ballard has found remnants of a civilization buried along the ancient shoreline of the Black Sea. The find supports the hypothesis linking the catastrophic flood that inundated the Black Sea, which was a freshwater lake about 7,000 years ago, to the biblical story of Noah and the flood in the Babylonian story of Gilgamesh. William Ryan and Walter Pitman III, of Columbia University’s Lamont-Doherty Earth Observatory, first suggested the idea three years ago in their book, Noah’s Flood. But missing from their story was direct evidence of a flooded ancient city from that time. On Sept. 12, Ballard reported the discovery of a rectangular area about 12 feet by 45 feet with carved wooden beams, branches and stone tools collapsed in the mud matrix. Pieces of ceramics at a second site seven miles away suggest another inhabited area. National Geographic Society and others sponsored the expedition to map northern Turkey’s coastline using sonar equipment. Undersea robots zeroed in on 200 square miles of what would have been prime beachfront property when the Black Sea was still fresh water.
Seismic profiling has revealed approximately 30 blind, transpressional faults running through Cook Inlet in south-central Alaska, in addition to the exposed Castle Mountain fault that has been known to be active since the 1960s. Peter Haeussler of the U.S. Geological Survey in Anchorage believes these faults were formed only in the past 1.5 million years and are active today. Over the past 15 to 20 million years, the Yakutat tectonic block has been pushing against the coast of Alaska, essentially “squirting part of the fore arc to the southwest,” Haeussler says.
Alaskans haven’t had to worry about a major earthquake in the region
for several decades. The magnitude-9.2 Good Friday earthquake that devastated
the region in 1964 was a subduction-type earthquake with a 700-year recurrence
interval. While Alaskans won’t experience another one of those for
a long time, they might have to deal with large earthquakes originating
in the fault zone just below the surface of Cook Inlet.