Legend once had it that Battle Ground Lake is bottomless. That’s not true, but it’s easy to see how such a myth might arise from the lake’s connection to murky mysteries of the distant past.
The lake was formed somewhere between 25,000 and 100,000 years ago when a big cloud of magma-heated groundwater exploded into the sky. The resulting 27-acre crater refilled with groundwater and silty deposits. Today’s lake bed is 60 feet at its deepest. But the crater floor hidden below is much deeper and older.
Battle Ground’s Lake’s unlikely contribution to the fossil record is highlighted in “Spirit Whales & Sloth Tales: Fossils of Washington State,” a new book about local geology and paleontology by a team from the Burke Museum in Seattle. The co-authors are paleontologist Elizabeth A. Nesbitt, former curator of invertebrate and micropaleontology, and popular science writer David B. Williams, a naturalist and curatorial associate. The book is lavishly illustrated with artistic renderings of long-extinct species and detailed photographs of fossils.
“Washington has amazing fossils and people don’t know it,” Nesbitt said during a phone interview with The Columbian. “When I came here from California, nobody was doing anything about Washington fossils. Our book is the first one.”
Maybe that’s because people tend to associate fossils with dinosaurs. While Washington’s fossil record has turned out to be incredibly rich — with everything from giant sloth skeletons to ancient seashells found high on today’s dry land — just one actual dinosaur bone has ever been found here.
Washington’s single dinosaur bone is dagger-shaped and 17 inches long. Scientists aren’t sure how it wound up embedded in the rocky, muddy shoreline of remote Sucia Island (one of the northernmost and tiniest of the San Juan Islands, near Canada).
The bone was discovered in 2012 by amateur (but permitted) fossil hunters looking for shell fossils called ammonites, which were contemporaries of dinosaurs. They never expected to stumble upon what appears to be the femur of a big carnivorous dinosaur.
“The dinosaur bone did not originate there,” Williams said. It may have been washed into the sea by a river. Or it may have been carried by the “conveyor belt of plate tectonics,” he said.
“Spirit Whales & Sloth Tales” describes how Washington’s fossil record has been erased or camouflaged by dynamic forces like plate tectonics and volcanism. New scientific tools and techniques pick up clues, nevertheless.
“We are almost in what you could call a golden age,” said Williams. “It’s an amazing time when the field has changed from a historical focus on just discovering and naming things, to a time when science is bringing the stories of species to life.”
Research at Battle Ground Lake offers a great example of innovative science connecting dots — literally dots of fossilized pollen as tiny as 5 to 200 microns wide, which must be studied with powerful microscopes. (Human hair is about 75 microns wide.)
Fortunately for science, these tiny indicators of ancient ecosystems tend to accumulate in orderly layers in silty lake beds, Nesbitt said. That makes for handy data collection, she said.
“I don’t think the public knows about fossil pollen, but easily it’s preserved in lake beds, and you take as deep a core sample as you can,” she said. “Pollen provides a detailed look at plant life. As the climate changes, the plant life changes.”
According to the book, scientists at Battle Ground Lake “collected the material they needed by coring directly through the sediment layers with a hand-operated piston corer. … They worked from an anchored platform in the middle of the lake and recovered more than 49 feet of vertical core, which spanned more than 20,000 years.”
Analyzing the core sample layer by layer and centimeter by centimeter has given scientists a detailed-yet-sweeping view of local conditions and changing ecosystems, Nesbitt said.
Twenty thousand years ago, the area around Battle Ground Lake was cold, dry, high desert (a little like today’s Eastern Oregon) and nearly within view of great glaciers to the north and east, according to “Spirit Whales & Sloth Tales.” Across the next 10,000 years, glaciers retreated, the climate got warmer and wetter, and different animal and plant species thrived and disappeared again.
“It was during this time of rapid climate change when the mass extinction of large herbivores, including mammoths, mastodons, and giant sloths, along with their top predators, such as saber-toothed cats and dire wolves, occurred across North America,” according to the book.
While active volcanism has hidden much of our local fossil record, Nesbitt said, it has also laid down handy time markers in the form of telltale ash layers. Those were found in the bed of Battle Ground Lake, too.
“These marker beds … are basically like little clocks,” said Williams. “That’s actually an amazing gift. Not every place has that. We have so many volcanoes, so many layers.”
“Spirit Whales & Sloth Tales” is packed with layer upon layer of stories stretching far beyond the relatively recent history of Battle Ground Lake to the unimaginably distant past of half a billion years ago.
The book outlines the basics of geologic time, the complex geology of Washington and how both professional and amateur fossil hunters have contributed to the fast-growing world of local paleontology.
“We want to stress that a big part of the story is the people,” Nesbitt said. “People who walk the beaches, walk the rivers, walk all over the place and find incredible fossils. A lot of people have been involved, and we like to share their stories.
“Many turn their discoveries right over to scientists for study,” she said. “A few don’t know what they’ve found, and (the fossils) sit in garages. We know there are a lot of beautiful things in people’s garages that we’d like to see.”
“There have been such fundamental changes in paleontology in the past 30 years,” Williams said. “I hope that people picking up this book will appreciate the complexity and beauty and experience a deeper connection to this place.”