The Badlands
Take a tour of Badlands National Park
is licensed under CC BY-NC-SA 4.0
The Badlands of South Dakota are much more than just the land to the south of Wall Drug Store. (If “Wall Drug Store” doesn’t make sense, your favorite search engine can give you a lot of information about South Dakota's strange but popular commercial tourist trap. Among other things, they have a great collection of western art, and a jackalope you can take pictures on, as shown in the VTRIP). Today, the Badlands may be most valuable for ecological reasons, because they preserve a wonderful piece of the shortgrass prairie that once covered much of the western Great Plains. The sea of grass and flowers that nourished the bison and the Native Americans of the plains has been almost entirely plowed under in most of the US West. But, in the upper prairie of the Badlands, the grass still waves in the breeze like an ocean, the pronghorn antelopes still bound through the grass, and you can, perhaps, imagine what the prairie once was.
As you can see in the VTrip (and image) above, the Badlands are carved into “rocks” that occur in nearly horizontal layers. But these don’t make giant cliffs such as the 3000-foot-high granite walls we will visit at Yosemite soon. Instead, the Badlands break down easily, so hikers on the trails must be careful to avoid slipping and sliding on loose material that becomes really, really slippery in occasional rains. (Hikers in Yosemite need to be careful, too!) The material at the Badlands was washed into where we now see it by small streams or blew in on the wind, and includes some loose ash from far-away volcanic eruptions that fell on the surface. Many of the layers at the Badlands are old soils that formed where we see them today and then were buried by newer deposits. Amazing fossils have been buried in these sediments, including bones of ancient alligators, saber-toothed cats, camels, rhinos, and more. (The National Park is essential in preserving these so that everyone can enjoy them!)
Earlier, we learned about obduction and subduction, and about volcanic eruptions and intrusions, processes that make hard rocks of the sort that you can see in the cliffs at Yosemite. Clearly, many things must have happened to turn such hard rocks into the loose pieces that washed into the Badlands, and then to turn those loose pieces into soils. And, just as understanding the mountain-building processes can help keep us safe, understanding the mountain-breaking processes is important for our well-being. We look at some of these mountain-breaking processes next, starting with changes called “Weathering”, because many of them are linked to the weather.