Fire in the Hole! Explosives Help Uncover Fossils At Dinosaur National Monument

Explosives were used recently at Dinosaur National Monument to help paleontologists reach fossilized bones of sauropods, which is what this skull came from. NPS photo.

In a field that often employs paint brushes and dental picks to unlock fossils from their encasing rock, you'd think explosives would be the last tool paleontologists at Dinosaur National Monument would reach for.

But, actually, a good, well-directed blast or two can come in quite handy when you have hundreds of tons of overburden to remove.

For instance, when you have a 40-foot-by-6-foot-by-10-foot slab of rock tilted at 70 degrees that is so hard and expansive that jackhammers are rendered impotent, well-placed explosives can help immensely. And that's where Dave Larsen, Steve Bors, and Tim George, licensed blasters from Rocky Mountain National Park, stepped in to help paleontologists reach a rich pocket of fossilized sauropod bones.

"It's not standard and it's not usual, but it's not experimental," says Dan Chure, Dinosaur's staff paleontologist. "We were fortunate to have a trained crew up in Rocky (Mountain National Park). They were able to come down and do this."

The blast area was located at the monument's Lower Cretaceous dinosaur quarry - the one that has produced the only complete brontosaur skulls from the last 80 million years of the Age of Dinosaurs in North America.

"We have been excavating at this quarry for a number of years," Dr. Chure explained today. "We started at the top of the hill where the bones were exposed and we were following the bones downhill. We just got to the point where using jackhammers and things like that really wouldn't work. The rock was really hard and there was a lot of it to remove."

Once the rock -- a mixture of sandstone and mudstone -- stopped the work, the call went out to Rocky Mountain for their blasters. Then, over the course of several days in mid-April, Messieurs Larsen, Bors, and George, using their expertise with explosives, blew away roughly 132 tons of rock that had been covering the fossils and exposed a significant amount of the fossil-bearing layer so more traditional excavation could continue.

For Larsen, this trip marked the second time he's traveled to Dinosaur to clear overburden with explosives. The first time was back in the 1990s, and he's also done similar work at Curecanti National Recreation Area. While the blasters from Rocky Mountain normally ply their talents on trail work, utility work, road work, and even building foundations, working side-by-side with paleontologists was not that unnerving.

"Like any activity, there's a little science behind it, or a lot of science behind it and some art," says Larsen, who also serves as Rocky Mountain's trails supervisor. "When we're out there it's more of an art. ... We proceeded cautiously at the start and through the whole process."

Working with varying amounts of ammonium nitrate and fuel oil, the blasters drilled a series of holes down into the overburden to set their charges.

"You're designing and placing the explosives in a setup and with delays to try and get the result you want, move the rock and dirt hopefully in a preplanned manner," says Larsen. "You can plan some direction to the blast. Again, that's where you call on your experience and try to get the movement in a certain manner, certain direction."

Dr. Chure says no fossils were damaged by the explosions.

"You do the blast and then you have to go in with hand tools and pull the blocks out and get down to a flat surface where they could drill more holes to get the explosives in," he explains. "It's kind of surgery with explosives."

Comments

An amazing process - but one that works if you have the right people involved.

Last summer at Mount Rushmore, I was a bit surprised to learn how much of the "carving" of those famous faces, including some fairly detailed work, was accomplished with explosives.