Today’s story is about one of earth’s natural history events involving a volcano, lots of plains animals on an ancient savanna landscape in northeast Nebraska, and how scientists have and continue to piece together the story of their lives and what brought them to an abrupt death. So hang on for a ride through geologic time, and get ready as we turn the dial in our “way-back machine” to the middle of the Miocene Epoch of the Tertiary Period.

Much of the plains states we know today were a vast open grassland type environment with scattered bushes and trees in a savanna setting. This plant life offered food and sustenance for the wildlife that lived during this episode of earth’s history. Fossilized plant life forms included Horsetail rushes, sedges, grasses and trees including walnut and hackberry. The waterhole settling on the plain was seasonally wet during a long rainy time frame and dry to almost dry the balance of the year.

Animals on this Nebraska landscape included a few species of fish in the ephemeral water hole that would later become a death trap. Salamanders, toads and frogs inhabited the water or its edges. Fourteen species of reptiles made a living here including a Giant Tortoise. Since this tortoise cannot live in an environment where freezing temperatures occur, this fact in itself helps tell researchers that the climate at that time was much warmer and milder.

And as a footnote for reference, people today should take note that these past natural climatic mood swings of earth happened, and continue to be on-going, without regard to modern day political correctness and its misguided and misinformed attempts to think man-kind is responsible for these changes.

Larger animals of this once broad landscape lists five species of birds recovered from the ashfall pit. On the mammal side of the ledger were pika, rabbits, an extinct horned rodent, small and large ground squirrels, a round-tailed beaver, deer mice, gophers, pocket mice, canines called bone crushing dogs and raccoon dogs, a bear dog, hedgehogs, moles, shrews, bats, peccary, camel-like species (four species), Musk deer, an extinct three-horned pronghorn, extinct three-horned deer, horses (five species) including three of which had three toes on each foot, hornless and horned rhinos and an elephant-like Short-jawed four-tusker. To date, more than 200 complete articulated skeletons have been exposed and left in relief within the ash beds of their death.

One thousand miles away, under a hot-spot of the earths crust, the North American continental plate was slowly sliding westward. Molten magma found its time and opportunity to erupt 11,930,000 years ago. The explosion and release of gases and volcanic material was at least 1,000 times greater than the 1980 eruption of Washington state’s Mount St. Helens. Geologists have named that particular volcano the Bruneau-Jarbridge for its location and the chemical composition of the ash from its giant cloud. By the way, the caldera of this volcano had a diameter of 50 miles! This same hot-spot is now located under Yellowstone National Park due to the continuous westward movement of the continental plate. And Yellowstone’s last eruption about 650,000 years ago left a 30 mile diameter caldera.

When the Bruneau-Jarbridge event took place, hot volcanic ash covered most of all of North America, dusting some places close by with over 24 inches of ash, central and eastern Nebraska got about 12 inches, eastern Nebraska and Iowa got less than 12 inches. The ash deposits were also easily swept by high winds into drifts, or eroded by winds and water from rains and floods to unequal depths. For Iowa geologists, trying to find volcanic ash is very difficult due to the action of at least eight glacial events during the past 2.1 million years. Advancing, retreating, and re-advancing ice episodes bulldozed away and thoroughly mixed glacial till soils with any remnant volcanic ash. Glacial systems were at the edge of what is now Ashfall Fossil Beds Historical Park and one reason why this rich and diverse paleoecological site was not destroyed by ice.

But the site was exposed by another natural geologic force … moving water. The action of erosion by running water over the land cut channels deeper and deeper, again following the mood swings of the earth’s climate shifts. Verdigre Creek flows north toward the Niobrara River in the vicinity of Orchard, NE. It was here in 1971 that Mike Voorhies, a paleontologist, went prospecting for fossils. He noted a partially exposed lower jaw bone of a large animal. He returned to properly excavate the animal’s bones only to note that the entire skeleton was also embedded with all of its bones properly positioned to reveal the true character of this animal. He learned later that this old waterhole setting had drifted deep with volcanic ash, killing small animals quickly followed in successive layers with medium animals and larger animals in the top zones.

Scientists also noted an abnormality of some rhino foot bones and on other bones of camels and horses. Smooth healthy bone also had sections of abnormal bone growth indicative of Marie’s Disease. A French pathologist Pierre Marie described this condition in concert with colleague Eugen von Bamberger in 1890. Doctors today call this bone malady hypertrophic osteopathy. This was evidence that larger animals at this waterhole breathing volcanic dust died a slow death due to the secondary results of organ diseases and in this case, lung damage from inhalation.

Thus began a long and successful story of more study, more excavations, and world-wide note duly taken that this site at Ashfall was so unique, so important, and so valuable, that it deserved serious time, money and resources to protect it. In 1978-79 major excavations took place with major funding from the National Geographic Society. The astounding results showed so many animals, all with intact skeletons, of rhinos (most numerous), plus horses, camels and birds.

The site now is home to a visitor’s center, and a large steel frame building covering 17,000 square feet of the major active excavation area. This building is called the Rhino Barn. Once inside, visitors can see on-going work to expose more animals, and one can also see artists drawings of many of the creatures this site has found who once lived on the Nebraska plains before the destructive volcano blew its top. Operation of Ashfall Fossil Beds Historical Park is a cooperative venture with the State of Nebraska Game and Parks Commission and the University of Nebraska State Museum. Ashfall is time capsule, telling the story of wildlife long ago, on a broad open savanna landscape. For any readers of this column that so desire to let their inquisitive minds wrap around conditions of our region of earth as it used to be 11,930,000 million years ago, make a commitment to drive 300 miles west on highway 20. You will be rewarded. You will be amazed. And you will be informed about death on the plains from a volcano.

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“The human mind may not have evolved enough to be able to comprehend deep time. It may only be able to measure it.”

– John McPhee,

Basin and Range

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Garry Brandenburg is a graduate of Iowa State University with BS degree in Fish & Wildlife Biology. He is the retired director of the Marshall County Conservation Board. Contact him at P.O. Box 96, Albion, Iowa 50005