Insight Into: The Lake Missoula Floods

Produced by the Space Telescope Science Institute’s Office of Public Outreach in collaboration with the NASA Earth Observatory.

All images, illustrations, and videos courtesy of NASA except:

·       Illustration of northwestern U.S. based on illustration from NOVA/WGBH “Mystery of the Megaflood” website

·       Glacial Lake Missoula painting courtesy of Byron Pickering

·       Dry Falls photo ©2004 Teri J. Pieper, www.byways.org

·       Palouse Hills photo courtesy of Lynn Suckow

·       Sea creature illustration copyright The National Library of Israel, Shapell Family Digitization Project _and The Hebrew University of Jerusalem, Department of Geography – Historic Cities Research Project

·       Photos of Mississippi River with debris courtesy of Thomas R. Machnitzki

·       Video of clouds over eastern U.S. courtesy of National Oceanic and Atmospheric Administration

·       Snow-to-rain animation by Marc Lussier, STScI

·       Satellite images of flooding in Birds Point–New Madrid Floodway courtesy of MODIS Today,

·       Space Science and Engineering Center, University of Wisconsin-Madison

·       Morganza Spillway video and photos courtesy of the U.S. Army Corps of Engineers

·       Photo of Mississippi River sediment plume entering Gulf of Mexico courtesy of Nancy Rabalais/Louisiana Universities Marine Consortium

·       Algae bloom photo courtesy of National Ocean Service/NOAA

·       Photo of fish kill on Grand Isle, Louisiana, courtesy of Kerry St. Pé

·       Mississippi River dead zone animation courtesy of National Oceanic and Atmospheric Administration

·       Photo of flooded farm near Vicksburg, Mississippi, courtesy of the National Weather Service

·       Map of Mississippi River course changes courtesy of the U.S. Army Corps of Engineers

 

Music courtesy of Associated Production Music

Written by Andrea Gianopoulos

Designed by Marc Lussier

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[SOFT MUSIC]

 

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A satellite view of the US with a white box over a section of the Pacific Northwest.

 

Text, 19,000 Years Ago, Northwestern United States. About 19,000 years ago an ice dam in the Clark Fork River Valley trapped water melting from the Cordilleran Ice Sheet.

 

An enormous glacial lake formed over what are now valleys west of the Rocky Mountains in Montana.

 

Glacial Lake Missoula reached a depth of about 2000 feet, nearly double the average maximum depth of the Great Lakes.

 

It held more water than Lake Ontario and Lake Erie combined.

 

A red dot marks the location of the dam. Text, When the ice dam gave way, Glacial Lake Missoula sent a torrent of water rushing across the landscape.

 

The towering wall of water and ice equal to 10 times the combined flow of all the rivers of the world shook and scoured the landscape.

 

Waterways spread on a map. A red dot marks Dry Falls. Text, As the deluge thundered toward the Pacific Ocean, it stripped away thick soils and cut deep canyons some 600 feet and 20 miles wide.

 

A red dot marks the location of Palouse Hills. Text, It roared across what is now eastern Washington at speeds approaching 65 miles per hour, carving what we know today as the Channeled Scablands.

 

Glacial Lake Missoula drained its 500 cubic miles of water in as little as 48 hours.

 

This cataclysmic event happened again and again before the ice finally retreated north.