"Are there floodplains on Mars? What caused the floods to make the floodplains? What is a dry waterfall?"
Giant Floods and Channeled Scablands
When Ice Age glaciers blocked the Columbia River, the Spokane River and the Clark Fork river (in Montana) they formed Glacial Lake Columbia, Glacial Lake Spokane and Glacial Lake Missoula. The evidence of these lakes can be seen in the lakebeds visible in various road cuts in eastern Washington and lap marks on hills and gravel deposits in Montana.
Glacial Lake Missoula, the largest lake, covered some 3000 square miles and was about 2000 feet deep. At some time the ice dam blocking the Clark Fork broke, sending nearly 500 cubic miles of water across northern Idaho's Rathdrum Prairie and into eastern Washington. The flooding washed away sand, gravel, rocks, and boulders leaving many channels.
In the LANDSAT satellite view (above) of the area you can plainly see the darker channels and lighter islands of the area known as the Channeled Scablands. The very dark areas are various lakes and rivers.
Geological evidence indicates that 89 or more such floods happened over the years as the ice dam blocked the Clark Fork, broke and re-blocked the river's flow.
In the NASA image of Mars at right there are shaped islands and channels that are thought to have been caused by a great flood. The Mars Pathfinder landed near the center of this image.
Click here to find out more about the coulees and canyons carved out by the Ice Age floods.
Here are some basic terms used in the tour. Find more geology terms in the Glossary.
- Ares Vallis
- Area of Mars where the Mars Pathfinder and Sojourner Rover landed.
- The deepest part of a river or bay.
- Channeled Scabland
- Area in Washington state where huge floods made channels in a large, deep basalt flow. Named by J Harlan Bretz during the 1920's in various publications. See also Glacial Lake Missoula.
- Long winding channel cut through lava formations. A term primarily used in the northwestern United States.
- A smooth plain covered by deposits of sand, gravel and rocks from floods.
- Lifting and removal of rock, dirt, sand and the like caused by wind, water, or glacial ice.
- The study of the changes in landforms due to volcanoes,
earthquakes, weather, floods, etc.
- Rounded rock fragments larger than sand.
- Ice Age
- A period in Earth's history when much of the continents are covered with ice sheets and glaciers.
- A flood created when a body of water held by a glacial dam breaks through the confining walls. The Lake Missoula Floods were jokulhlaups.
Kids' Cosmos… Expanding Minds Beyond the Limits of the Universe
P.O. Box 14077, Spokane, WA 99206-4077
© 2011 Kid's Cosmos
This tour created with the support of: