Yardang
A yardang is a rock ridge feature caused by wind erosion and water erosion. Some are found in a dried-up riverbed.
Yardangs may also be found in deserts and may form very unusual shapes and some resemble various objects or even people.
An example of a famous yardang is "Hole In The Rock" in a park in Phoenix, Arizona that has a large window shaped hole in it. There is another example in Window Rock, Arizona.
Pictures from Mars show that the yardang ridges occur on a massive scale there, giving visual support to the theory that Mars has once had ground water.
Reference
- "Yardangs on Mars." NASA SSE Multimedia Gallery. Accessed on March 21, 2005.