October 1, 2010

Mammoth Site of Hot Springs, South Dakota

Today we migrated about 30 miles south to Hot Springs, South Dakota. After setting up camp, we headed over the the Mammoth Site at Hot Springs, the largest mammoth bone site in North America. This was Hilina's dream come true and she was in pure ecstasy the whole time.

Hot Springs is famous as a mineral bath resort, with waters between 87-98 degrees F bubbling up in 107 springs in the area. Well, approximately 26,000 years ago, these same bubbling springs set the stage for the largest accumulation of mammoths anywhere, including La Brea Tar Pits.

Hilina running between exhibits results in blurry images
Back during the Ice Age, a limestone cave under the soft shales above collapsed, forming a sinkhole. Since there were all these warm springs around, the sinkhole formed a deep warm pond. Despite the frigid temperatures all around, the edges of the pond remained ice free and a thick layer of grasses and vegetation formed around the edges of the pond.

This was very enticing to mammoths living in the area and they would head down to the edge of this sinkhole to eat or drink. But, this shale which formed the rim of the pond is very slippery when wet and when they tried to get down to the water, they slipped in and were unable to pull their 10-ton bodies out with the slick sides.

Eventually, the pond filled in with sediment and was cemented together by the calcium carbonate from the springs. Over time, the surrounding shale actually eroded away faster than the pond sediments cemented together for form a reversal of topography. The sinkhole was now a hill.

The arrows show where mammoths stepped and compacted mud in the sinkhole
At this stage, 52 mammoth skeletons have been unearthed, but there remains another 20+ feet to dig through and it could take another 30 years of digging to get to the bottom of the sediment. Only 4 of these were the smaller and more famous Woolley Mammoths. Most of them are the much larger Columbia Mammoth. But, some test drills have shown that it is mammoths all the way down. It is estimated about 3-7 mammoths fell into the pit every ten years. So, it wasn't a massive die off, just the occassional accident.

It isn't just mammoths though, they have found other Pleistocene animals as well, such as camels, llamas, short-faced bears, pronghorns, wolves, coyotes, prairie dogs, and a whole host of small mammals and rodents. They have also found a few fish, amphibians, and mollusk shells.

Hilina holding a mammoth tooth cast
Hilina really enjoyed the children's area, where she got to dig through the sandbox looking for bones. She said, as we were leaving the museum "Someday when I am older, I am going to come back to work here". Amazing...Maybe someday she will.

Replica of an eastern European Mammoth House
These were apparently common around 14,000 years ago in the Poland-Russia area. It required the bones from over 100 mammoths to make a house large enough for 6-10 people. Apparently, entire villages of these were found in the Ukraine (well up to 10 or so of them).

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