Want to stay on top of all the space news? Follow @universetoday on Twitter
During the 16h century, Spanish explorers ventured north from Mexico looking for gold, jewels, and the legendary seven cities of Cibola. What they found instead were some of the most amazing natural geological formations in the world. They were in fact the first Europeans to set eyes on what is now known as a Butte. By definition, a Butte is a conspicuous isolated hill with steep, often vertical sides and a small, relatively flat top. The word “butte” comes from a French word meaning “small hill”.
Buttes are not to be confused with Mesas. Definitions of the surface areas of mesas and buttes vary. One source states that a mesa has a surface area of less than 10 square kilometers, while a butte has a surface area less than 1,000 square meters. Another source states that the surface area of a mesa is larger than 2.59 square kilometers. Some simply define a mesa as a landform that is wider than it is high and a butte as one that is higher than it is wide.
A butte’s characteristic shape is due to the layers of rock forming them. The top layer of a butte is a hardened layer of rock that is resistant to erosion. This top layer, called the cap rock, is usually composed of sedimentary rock, but sometimes is the remains of cooled and hardened lava that had spread out across the landscape in repeated flows from fissures or cracks in the ground. Beneath this flat protective cap of rock are horizontal layers of softer sedimentary rock. To varying degrees, these layers are not as resistant to erosion.
These landforms are found in arid and semiarid regions. Because water evaporates quickly in these normally dry environments, plants and other ground cover are scarce. Left exposed to the action of running water, the bare sides of the softer rock layers of buttes are eroded away over time. The base of these landforms is often gently sloped, contrasting with the almost-vertical sides leading down from the top. Rock material that has been eroded from the sides is carried downward, forming this sloping base.
Buttes can be found all over North America, though they are most commonly found in the arid regions of the American Southwest. Other examples of this geological wonder are to be found in Saskatchewan (Castle Butte), Oregon (Black Butte), and South Dakota (Bear Butte).
We’ve also recorded an episode of Astronomy Cast all about Plate Tectonics. Listen here, Episode 142: Plate Tectonics.