Types of Sand Dunes
"How big are sand storms on Mars? How are sand dunes formed and are there different types?"
Sand Dunes and Martian Winds
In the thin atmosphere of Mars the winds can blow up to 100 km/hr. The dust storms on Mars can be quite large with some engulfing the whole planet. Here is a NASA comparison of a dust storm on Mars to one on Earth over the coast of Africa. Note that the center T-shape of each storm is similar. Click on image for a detail view.
Without surface water and plants to help keep the dust and sand in place, Martian sand dunes continually travel across the planet. The Planetary Society had a microphone project contained in the Martian Polar Lander so that we could hear the winds and sounds of Mars. Unfortunately the lander failed to land safely.
Shifting sand dunes like those found in the Hebes Chasma area on Mars (left) can be found near Moses Lake and Pasco, Washington.
Whenever winds pick up, dust and sand eventually the particles are redeposited as the wind loses its force or velocity. As a small pile of sand slows down the wind more sand is deposited creating a larger pile. This larger obstruction slows the wind further and eventually the pile of sand becomes a sand dune.
Scientists have catagorized the various types of dunes based upon their shape and how they were formed.
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. Click image for a NASA discussion of Martian Sand Seas that will open in a new window.
"This dramatic image shows a field of dark sand dunes in the Nili Patera region of Syrtis Major. The shapes of these dunes indicate that wind has been steadily transporting the dark sand from the right/upper right toward the lower left. This picture was taken on the first day of the Mars Global Surveyor (MGS) Mapping Phase during the second week of March 1999. It shows an area 2.1 kilometers (1.3 miles) wide at the full commanded resolution of 3 meters per pixel. Illumination is from the upper left." Caption and Photo Credit: NASA/JPL/Malin Space Science Systems
The sand dunes in the photo at left are just south of Moses Lake, Washington, and are used for recreation by those with dune buggies. The sand is black from basalt grains mixed in with white and gray from lakebed silt. Click image or here for types of sand dunes.
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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.
- 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 Channeled Scablands.
- Lifting and removal of rock, dirt, sand and the like caused by wind, water, or glacial ice.
- 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.
- 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.
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