Ashfall Fossil Beds

The ash cloud that descended on the water hole was not necessarily a visible cloud.

"The sky probably got dark," explained Voorhies. "It probably first was like a haze. It’d be like the air in L.A. You’d have a haze of material that came in, the sky would get darker and there’d be this stuff coming out of the sky. Since these animals had never seen snow this is probably something that was entirely new to them."

It appears birds such as cranes, hawks, and vultures died quickly, possibly within hours of when ash dust started falling. Their skeletons are found at the lowest levels of the ash beds, suggesting they were among the first to fall. Pond turtles were also among the early casualties.

The dust came down hard and fast. The animals with the least lung capacity perished by the herd as grey powder covered the land. The fossil layer containing the small deer, three-toed horses, and camels is higher than the remains of turtles and birds, suggesting the small animals survived a little longer. The ages of the animals and their states of preservation suggest they died in close succession.

Ash hung in the air and coated every bite of vegetation. Each step kicked up more ash, contributing to the slow death from suffocation. Skeletons of camels, horses, rhinos and other large animals show they had a lung condition known as Marie’s Disease. The animals were probably thirsty and suffering from high fever.

"After several weeks of inhaling the ash their body temperatures went way up and it probably felt good to them to lie down in the mud," Voorhies noted.

It’s unlikely that all the fossils in the ash bed were animals that just happened to be there at the time, Voorhies said. The sickened animals probably came because they knew they could get water there. Rhinos survived the longest, up to five weeks.

After all had died, the remains of the animals, small and large, were covered by the blowing, drifting ash. A few scavenging meat-eaters disturbed carcasses, but most bodies stayed in the same position in which they died. Some still had their last meals in their mouths or stomachs.

Ash remained in the air for years. Voorhies said, “The only thing that would make the ash stop blowing was when it fell into the water. The water would actually capture the ash and when you look at the fossil bed here at Ashfall, you can see that it consists of about 600 little separate layers of volcanic ash. Each one of those layers would be where a puff of wind had delivered a cloud of dust. It was captured by the water in the water hole. It fell to the bottom as a layer of ash mud."

Gradually, five to six feet of ash covered the bodies. "You could look any direction and there wouldn’t have been anything alive, probably for who knows, several years before eventually the place where the water hole used to be was completely destroyed by the ash fall," Voorhies explained.

Voorhies said plant life returned to Ashfall when a river went out of its banks and started depositing sand over the top of the ash bed. "Eventually, the same species of rhinos and camels and horses that had been destroyed by the ash moved back in and started eating the grass and shrubs that were growing here in the sand from the ancient river," he said. Mount St. Helens in Washington saw the return of deer and elk just ten years after its volcanic eruption in 1980. "The same thing happened at Ashfall," explained Voorhies. "We don’t have a good handle on how long that took, but as far as we know, nothing became extinct because of the ash fall."