[236.5 MM 64]
A last look at the floodplain before we head south on Highway 17 and continue to Moses Lake and Interstate 90.
[210.2 MM 38]
Junction with State Highway 282, we stay to the left and continue towards Moses Lake.
[245.3 MM 3]
Enter Moses Lake and follow signs to Interstate 90 [251.0] and head East at Mile Marker 180 on I-90. Watch for gravel bars, basalt outcroppings and sand dunes.
Shifting sand dunes like those found in the Hebes Chasma area on Mars (right) can be found near Moses Lake and Pasco, Washington.
When floodwaters backed up behind Walula Gap, near Walla Walla, Washington, they lost their ability to carry eroded loess, sand, gravel and other debris. The sediment from these short term lakes became the source of the sand in this area.
The old lakebeds are very flat making it easier for winds to pick up sand and dust. Also, as the Cascade Mountains rose, they blocked the rainclouds coming in from the Pacific Ocean causing the region to become semi-arid (very dry). This "rain shadow" effect continues to keep the average rainfall of the plateau very low.
Sand Dunes and Martian Winds
This image shows the sand dunes of Nili Patera, Syrtis Major. The size and shape of a dune depends on the ability of winds to pick up and carry sand and the direction the winds blow. In the thin atmosphere of Mars winds can blow up to one hundred km per hour and wind storms can cover the whole planet.
Here are some basic terms used in the tour. Find more geology terms in the Glossary.
- Volcanic rock caused by partial melting of the Earth's crust.
- Large rock or boulder carried by water or glaciers and left behind.
- The study of the changes in landforms due to volcanoes,
earthquakes, weather, floods, etc.
- Rounded rock fragments larger than sand.
- Fine dirt deposited by wind usually from arid or glaciated areas.
- Rain Shadow
- A mountain or mountain range that blocks rain clouds just as an object might block sunlight to form a shadow. Areas in the shadow are more dry as a result.
- Collection of sand, silt, gravel and organic material that sinks to the bottom of a river, lake or ocean. Some or all of these materials may be present.
Kids' Cosmos… Expanding Minds Beyond the Limits of the Universe
P.O. Box 14077, Spokane, WA 99206-4077
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