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Waco Mammoth National Monument
The Waco Mammoth National Monument is a paleontological site and museum in Waco, Texas, United States where fossils of twenty-four Columbian mammoths (''Mammuthus columbi'') and other mammals from the Pleistocene Epoch have been uncovered. The site is the largest known concentration of a single herd of mammoths dying from the same event, which is believed to have been a flash flood. A local partnership developed around the site after the initial bone was discovered. The Waco Mammoth Foundation worked in partnership with the city of Waco and Baylor University to develop the site. In 2015, they successfully sought the National Monument designation to bring the expertise of the National Park Service into the partnership.〔
==History==
Columbian mammoths lived 10,000 to 1 million years ago. They migrated to North America and as far south as Nicaragua. The Columbian mammoth was a herbivore, with a diet consisting of varied plant life ranging from grasses to conifers.〔(【引用サイトリンク】url=http://www.ucmp.berkeley.edu/mammal/mammoth/about_mammoths.html )〕 At this time, the Central Texas landscape consisted of temperate grasslands and savannahs surrounded by river floodplains.
How the animals at the site died is unknown, but there is no evidence that humans were involved. The current theory is that approximately 68,000 years ago, at least 19 mammoths from a nursery herd were trapped in a steep-sided channel during a flash flood and drowned and/or were buried by mud. A camel was also trapped and killed during this event. Later floods buried the remains. A second event took place sometime later. During this event, an unidentified animal associated with a juvenile saber-toothed cat (genus ''Smilodon'') died and was buried. The third event claimed the lives of a bull mammoth, two juvenile mammoths, and an adult female. Approximately 15,000 years after the nursery herd was trapped, these animals also appear to have been victims of rising water, unable to escape due to the slippery slopes of the surrounding channel.
Optical dating of the fossils was done by optically stimulated luminescence (OSL). OSL uses light to excite electrons and cause the emission of photons. The photons can be sensed and measured to calculate when the test sample was last exposed to the sun. The soil near the mammoths remains was examined using OSL to determine how long the minerals were buried. As the soil was buried at the same time as the mammoths, determining when the soil was last exposed to the sun would correlate to the time when the mammoths perished.
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