Flood Plains on Earth and Mars
Key to Mile Markers and Highways Notation
[1.3 MM 282 US 2]
(Description of point of interest)
|Trip Mileage||Mile Marker||Highway|
|1.3||MM 282||US 2|
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[222.6 MM 96 State 17 S]
Passing through the town of Soap Lake, we stay on Highway 17 and travel south.
[228.6 MM 72]
We reach the huge flood plain that resembles Ares Vallis on Mars where the Mars Pathfinder mission landed. Turn left onto Hatchery Road for a closer view of the large boulders strewn across the fields. The large boulder pictured below is 59 feet wide by 26 feet high!
|"Both sides of the road for as far as you can see there are hundreds of boulders of all shapes and sizes. Most are medium sized at about 2 feet across. It has not been farmed and so the rocks are in the same place they have been for thousands of years." [Draggoo]|
|"Flood deposits here are up to 50 meters (160 feet) in thickness and are the product of sedimentation from floodwaters discharging from Lower Grand Coulee. Flow from the confined flood channel widened in this area as it escaped the Lower Grand Coulee; the depth of flow decreased and the velocity (speed of flow) diminished accordingly, thereby allowing the deposition of the coarse bouldery gravel deposits in this area." [Buchanan]|
The photo at left shows how sand flows around larger objects as ocean waves move across the beach. The red arrow points to one area where the sand dips around a rock. A similar but larger effect is seen around the giant boulder (above) and other large boulders in the flood plain. This indicates a similar action during the floods.
Note also in the photo the ripples in the sand caused by flowing water. They are like the large curent ripples we have seen on our trip.
September 24 - 30, 1995 brought Arizona State University professors and a group of NASA and JPL engineers to this field. This was during the design and testing phase of the Mars Pathfinder and Sojourner rover. Click below to read about the tour. At AstroCon 99, the annual convention of the Astronomical League, a group of amateur astronomers took a Bus Trip to Mars tour. Click here to read the article about the event in the Webfooted Astronomer, the newsletter of the Seattle Astronomical Society. Click here to go to the Spokane Astronomical Society's Past Events, Astrocon 99 page.
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Field Trip to the Channeled Scabland of Washington
[230.6 MM 72]
We return to Highway 17 and continue south.
Comparison to Ares Vallis Flood Plain
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.
- Current Ripple
- Mark left on streambed from water current usually less than an inch high and a few inches between the tops (crests) of each ripple. The giant ripples from Lake Missoula floods are as much as 35 feet high and several hundred feet between. See also Ripple Mark.
- Rounded rock fragments larger than sand.
- Ripple Mark
- See also Current Ripple. Parallel, elongated mounds of sediment formed in wind or water currents. Large ripple marks found in the Channeled Scablands were the most convincing evidence for the Missoula Floods. See also Glacial Lake Missoula.
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