This was an incredibly cool stop. It is an active mammoth excavation site with an interpretive center built around it. The mammoths were originally found in 1974 by a developer, who was bulldozing the area in preparation for putting in a housing development. The bulldozer operator was enrolled in a night class in paleontology, and when his dozer unearthed some bones, he contacted the paleontology professor, which lead to the amazing find. Eventually, the developer sold the site to a newly created non-profit organization at cost, and now there's active excavation you can watch in progress, a museum, and interpretive center.
What they've learned is that originally, the area had a layer of clay and silt on top of a karst layer. The karst (limestone) eroded away from groundwater movement, till the point where the surface collapsed, forming a sink hole about 120 x 150 feet. The sink hole filled with water about 65 feet deep. Paleontologists theorize that the wet area had lush vegetation, and that the clay/slilt area on the edges was wet and slick. So, mammoths would approach the area to eat the vegetation, fall in, and be trapped in the steep-sided sink hole.
The mammoths fell in for about 700 years. Many of the bones dissolved in the warm water (remember this is very close to Hot Springs, SD) and disappeared, but the tusks largely stayed. So, they have counted tusks and divided by two and to date have found at least 61 mammoths. So about one fell in every 10 years, I suppose. They have also found a wide variety of other wildlife, including giant short faced bear, llama, camel, prairie dogs, wolves, fish, and many smaller mammals. Here's how a lot of it looks.....
A set of tusks and skull....
Another view of the dig site. This is incredibly delicate work, largely done with dental tools, tooth brushes, and brooms. Every bit of sediment that is removed is carefully screened for the tiniest fossil, and then bagged and stored away. It's tedious. I wouldn't have the patience.
Here's a reproduction casting of a Columbian Mammoth skeleton. Its about 4 meters high. The original bones are too delicate from being immersed in the hot water for so long and won't support their own weight, so castings are used to make recreations like this one.
Here's a pelvis. Paleontologists are able to determine the animal's sex by the shape of the pelvis. This allowed them to determine that almost all the mammoths that fell in are males, which may relate to current elephant behavior, which have matriarchal societies. I.e., apparently these males didn't have a female leader to keep them from doing stupid things, so they fell in :-)
Rear legs, the left one kinda coiled up in a G-shape. Note the dental tools and other tools used for the excavation. We were here on a Sunday, so no one was working in the dig itself.
Same mammoth, but you can see a bit more of the pelvis and skeleton.
You can see this bit of red sediment, which marks the edge of the sinkhole. It's red because of the high iron content in the sediment creates rust on exposure to air. The building is built just on the outside edge of the sinkhole.
This is a fairly complete skeleton.
This shows the relative (full-size) sizes of various elephant relatives. Pygmy mammoth, Asian elephant, Wooly mammoth, African elephant, and Colombian Mammoth, in increasing order of size. At this site, they found both Wooly Mammoths and Columbian Mammoths, which they thought had differing habitats. However, there were only 3 (I think I remember) Columbian Mammoths found. The rest of the bones and tusks are from the smaller Wooly Mammoths. The Pygmy mammoths are only found in the Channel Islands of Southern California.
Here's the actually area where the water entered the spring. Notice the ripples in the sediment.
Our guide said this is the most complete skeleton, but it's upside down and looks like a mess.
Here are full-size profiles of the Wooly and Columbia Mammoths, with me standing between them.
A mammoth rear end...
and sketch of where the bones came from....
One unusual fossil they found was the skull from a Giant Short-faced bear (which I believe is the largest known bear species). This diagram shows the comparative size of that bear with other bears that are still alive. Notice the joke on the right side of the diagram :-)
This short-faced bear skeleton is a replica from some a real skeleton found at another location. It's BIG, and kinda makes you think.
And a full-sized replica of a Columbian Mammoth (~4m high). Note the tour guide in the black shirt for scale.
Here's something very interesting to me. With global warming and the loss of glaciers, scientists are finding actual mammoths (and other animals) that got entombed in ice and mummified, and then are exposed as the ice melts. These carcasses are intact and dry, and allow scientists to see the color of the fur. Also, scientists can collect DNA from the hair of the mummified animals. This allows them to exam the relationship between these and current elephants. Unfortunately, there is no DNA left in the mammoths from the sinkhole. Apparently the hotwater destroyed / dissolved all DNA. I think it said these were replicas of mammoth infants found in Asia.
Generally speaking, it seems that most mammoths died out at the last period of deglaciation, or around 10,000 years ago. The most recent known example are dated to about 3750 BC in Alaska, and 1650 BC in Wrangel Island (eastern Siberia, just across the Bering Strait from Alaska). Scientists disagree on the cause of the extinction - whether it was due to man, climate change, asteroids, or other cause.
As you can imagine, we've been to many, many, many, many interpretive centers, museums, and the like in our travels on this trip and before. I have to say that this was probably the best we've ever been to. They really did a great job telling the story of these amazing animals, and connecting the visitor to the animals, their story, and paleontology. I give it five stars.
You can check out their website at Mammoth Site at Hot Springs. There's a couple Wikipedia entries that are worth checking out on the Mammoth Site and on mammoths in general.