buttes and mesas

Mesas and Buttes

	In the image at the left are three buttes and part of a mesa. At some time in the past the whole was covered with a light colored deposit. That deposit has since worn away except for the light areas that make up the buttes and mesa. These forms are similar in size and shape to the landscape in Monument Valley.
In the mesas to the right there is a great deal of dust causing a softer appearance to the whole landscape. Some dark streaks are apparent. They are caused by material sliding down in an avalanche type of movement. They seem to occur only in the warmest places--where the temperature has risen to above the melting point of water.
	The image at the left contains parts of three mesas. This is all that is left of a layer that covered the whole area.
The mesas in the image to the right are larger and have fairly steep walls. Notice how material is arranged around the larger mesa as more or less concentric circles. Thiscircular arrangement may be due to material moving away from the mesa.
	The circular shape of the buttes at the left suggest a complicated history. The buttes may represent old craters that were filled and covered over with a layer of material which eventually hardened into rock. Then, all the material outside of the craters eroded away, leaving what you see below. Remember, on Mars the surface can be billions of years old. Erosion on the Earth has removed most of our oldest rocks. A long history of water drived erosion on Earth has removed many geologic features. Also, every few hundred million years plate tectonics recycles the surface.
Cap Rocks Mesas and buttes often hold their shapes until the top layer of rocks, called the cap rock erodes away. This cap rock is often more resistent to erosion than the rocks beneath. In the picture at the right, the cap rock has eroded away form the top butte, resulting in a small tip with a wide base. The lower formation is a mesa that still retains its cap rock. So the top is flat with steep walls for a short distance. These type of formations are common in Momument Valley
The image on the right shows the cap rock of a butte. These rock formations look similar to the ones above, although they lie at some distance from each other. The layers may have formed under a sea. It is possible that the same sea formed both sets of layers. That would mean that it was quite a large sea.
	The picture to the right shows a series of cliffs, each having a cap rock that protects the the layers beneath. Once the cap rock erodes, the rest of the layers go too. Erosion resistent cap rocks often cause cliffs to form.
The image to the right shows a mesa that is in the process of eroding. Parts of it have just started to erode. Other parts are in an advanced state of erosion. This view shows us how many features on Mars came to be. Revised January 2007 For more images click here. Return to Home Page.