* Astronomy

13,350 years ago the glacial Lake Iroquois broke out from behind the Adirondack Mountains and the northern ice sheet.
It was three times the size of modern Lake Ontario.
As the natural ice dam collapsed, floodwaters rushed down the Hudson River Valley; past modern Manhattan, Brooklyn, and Staten Island; through an earthen dam where the Verrazanno-Narrows Bridge now stands; and across another hundred miles into the North Atlantic.
The water level in the ancient Lake Iroquois dropped 120 meters, and rocks the size of Volkswagens were moved hundreds of miles downstream and out into the Atlantic.



An ice dam forming a large Ice Age lake collapsed 13,350 years ago, sending a flood down the Hudson River Valley. The flood of fresh water into the ocean also caused dramatic climate changes.
llustration by Jack Cook, WHOI.

According to Jeff Donnelly, a geologist , who is a fellow of both the Ocean and Climate Change Institute and the Coastal Ocean Institute at the Woods Hole Oceanographic Institution (WHOI), the catastrophic flood reshaped the landscape and may have triggered a brief but global period of colder climate known as the Intra-Allerod Cold Period. The torrent from the glacial lake would have thundered into the North Atlantic, adding a vast freshwater "lid" on the ocean surface that could have rearranged ocean circulation and changed climate patterns.

Large discharges of glacial water into the ocean causing climate fluctuations were long suspected by scientists, but linking discharge events like the Hudson flood with individual climate changes has been difficult because of the challenges in pinpointing the location, timing, and amount of the discharges.
Donnelly and colleagues analysed sediments from the Hudson River Valley, which extends under water on the continental shelf . On huge sediment lobes on the shelf, where sediments are normally the size of sand grains, they found car-sized boulders—which were likely pushed there by the great flood.
The team also analysed ancient pollens deposited by the flood in sediments near the Tappan Zee Bridge and the Holland Tunnel, as well as walrus fossils buried by the flood in the offshore sediment lobes. The results precisely dated—for the first time—the discharge from Lake Iroquois and linked it to the Intra-Allerod Cold Period.
Donnelly and colleagues described the historic flood and its effects in a February 2005 paper in the journal Geology.