The following article shares highlights and insights from one of our Expert Series events, which are exclusive for Young Scholars and their parents.
Millions of years ago, North America looked quite different from what we see today. Although we think of rhinoceros, camels, elephants, and crowned cranes as belonging in Africa, these animals once roamed the Great Plains, sometimes in massive herds. They mowed down grasses, visited waterholes, and existed as part of a complex web of life. But how do we know? No one was around back then to take notes, record video, or pass along their intel. The only way to solve the mysteries of what North America looked like back then is to hunt for clues left behind in the earth.
Fortunately, there are remarkable paleontology sites, including the Ashfall Fossil Beds in northern Nebraska, that tell a tale of a once-thriving ecosystem. Herds of large mammals roamed grasslands dotted with trees. They visited waterholes and tried to avoid being eaten by the predators of the day: bone-crushing dogs and thin-sabered ‘cats.’ But one day a supervolcanic eruption in what is now Idaho blanketed the area with more than a foot of ash, killing many of these animals and burying them for millions of years.
Fast forward to modern times, when a 17-year-old farmhand and his dad discovered a rhino skull eroding out of a hillside. Years later, paleontologist Mike Voorhies visited the site and found another skull sticking out from the bluff. He started digging, and now, more than 50 years later, the Ashfall Fossil Beds have revealed more than 200 complete skeletons of the animals that once lived in the area. And that’s not all. The site has revealed clues about not just the animal life, but also the plants and geology of the time.
Highlights from This Expert Series Event
- Twelve million years ago the Great Plains of North America were home to animals we now associate with Africa: elephants, rhinos, zebra-like horses, camels, crowned cranes, and more.
- A supervolcanic eruption at the Bruneau-Jarbidge site in modern-day Idaho ejected massive amounts of ash into the atmosphere—enough to leave traces across the entire continent and a foot across Nebraska, more than 1,000 miles away.
- The ash killed grass-eating mammals and many smaller animals (birds, turtles). They gathered at a waterhole in what’s now Nebraska, where they perished. Their bodies were buried in volcanic ash, which cushioned and protected them for millions of years.
- In addition to the animal skeletons, scientists have found grass and tree seeds that have helped them reconstruct the ancient landscape.
- Fossilized ripples and rhino footprints at the bottom of the ash bed helped researchers determine that the waterhole was, in fact, a waterhole. Diatoms revealed that it filled during the rainy season and dried up during the dry season, providing important information about climate.
- Giant tortoise fossils also tell us that the climate was mild. Unlike today’s climate with summer and winter, it stayed above freezing all year long.
- We know the eruption happened 12 million years ago thanks to radiometric dating. Zircon crystals contain uranium atoms. These decay over time into lead at a very specific rate. By comparing the number of uranium and lead atoms in a crystal, scientists can calculate how long ago the crystal shot out of the volcano.
Things Students Can Do to Explore this Topic Further
Take a good look outside. What kinds of plants and animals do you see? Now close your eyes and imagine what it looked like millions of years ago. Draw a picture of this ancient world. How can you know that these plants and animals existed here at one time?
Visit a natural history museum near you and take a good look at the dioramas and skeletons. What kinds of animals lived where you are now? There may be dinosaurs from more than 65 million years ago. Are there fossils of large land mammals? They took over after dinosaurs went extinct, but we don’t hear about them as much.
Talk with a paleoecologist to learn more about what your area looked like in the ancient past. Ask them how they know—what evidence have they used?
Diatoms are found in every body of water (and even on the feathers of some water birds!). These single-celled algae make glass houses. Collect samples of water from a pond. Diatoms sink, so collect a bit of sediment from the bottom of the pond. Place a few drops of the water/sediment mixture on a slide and take a look under the microscope. Do you see any diatoms? What other single-celled organisms can you find?
You can learn more about the Ashfall Fossil Beds at https://ashfall.unl.edu/.
You can learn more about how researchers pieced together the story of Ashfall in my book, Rhinos in Nebraska: The Amazing Discovery of the Ashfall Fossil Beds (Henry Holt, 2021).
Nebraska is home to some of the best large mammal paleontology sites in the world. Learn about the researchers who study Nebraska’s past at Paleo Sleuths: http://paleosleuths.org/. You can learn about some of the large mammals that once roamed the Plains, learn about the various dig sites in the state of Nebraska, and even watch a documentary film about the Paleo Sleuths and their detective work.
Diatoms are one of the most important—but largely unknown—organisms on the planet. They produce the oxygen in one out of every five breaths you take! Check out some of the incredible diversity of diatom houses and learn more about these essential organisms at https://diatoms.org/what-are-diatoms.
Authored by: Alison Pearce Stevens
Bio: Alison Pearce Stevens has been chased by a trumpeter swan, bitten by a bronze-winged duck, and served as a climbing wall for geckos and baby bats. She used to be a beekeeper and still thinks pollinators are some of the coolest things on the planet. Once upon a time, she was Dr. Stevens, science professor, until life took her overseas, at which point she started writing about science and nature for kids, because she’s an educator at heart and had to find new ways to share cool things with the world’s most curious people. Dr. Stevens has developed exhibits for natural history museums in Nebraska and Minnesota and written hundreds of articles and books about science for kids. You can find her work in Science News for Students, Highlights, ASK, and other kids’ magazines. Her latest book is Rhinos in Nebraska: The Amazing Discovery of the Ashfall Fossil Beds (Godwin Books/Henry Holt BYR).