‘Expedition Yellowstone’ a Hot Ticket for Schools

They crept up to the rock ledge, belly to the ground, to gaze at the hot springs just feet below. Peering through steam, the fourth-graders watched as water washed across a colorful and intricate terrace of mineral deposits.

“I like Yellowstone,” Bobby Daigle proclaimed upon coming to his feet, white dust clinging to his clothing.

Daigle’s 22 classmates and teacher from Silverthorne, Colo., would almost certainly agree, even after hiking through a downpour of cold rain early one recent morning in Norris Geyser Basin. The goal of this program, called Expedition Yellowstone, is to transform youthful curiosity about Yellowstone National Park’s natural wonders into a scientific learning experience for grade-school kids.

The students were given two mysteries to solve while inspecting the hot springs formation, known as Angel Terrace, just outside Mammoth Hot Springs in northern Yellowstone.

The first: What is that crumbly white rock all over the terrace, which dusted Daigle’s clothes? The second: What happened to the dead trees poking out of the ground nearby?

Recalling an earlier discussion of Yellowstone geology, fifth-grader Samantha Gammel posited that the white substance was limestone. To test that theory, she would use an acid solution.

“You put it on the limestone, and if it bubbles, it’s limestone,” she beamed.

But Samantha had an advantage. The Silverthorne Elementary students studied rock classifications before their expedition to Yellowstone.

Fourth-grade teacher Kirsten Shult said she incorporated National Park Service materials into her lessons to help prepare the students.

“It ties right into what we’ve been studying in the classroom,” Shult said. “Now they get to take the classroom out here and actually try it in real life.”

Samantha and her fellow students took their rock to park ranger Heidi Doss, who dispensed two drops of “magic Yellowstone” hydrochloric acid solution. The limestone bubbled under the approving smiles of five children.

In central Yellowstone lies a caldera that measures 45 miles long and 30 miles wide. It’s a reminder of the last giant volcanic explosion more than 600,000 years ago. Pressured by a mass of molten rock known as the Yellowstone hot spot, a volcano still slumbers below the caldera. More recent lava flows left rhyolite as the dominant rock in that area.

Limestone, however, is a sedimentary rock common in areas outside the caldera, including the students’ location in Mammoth Hot Springs.

But the park ranger had more up her sleeve. When the students gathered in a circle to discuss the mysteries, Doss said the white rock is actually called travertine, a particular form of limestone that was deposited on the surface by a hot spring that once flowed there.

“As the hot water travels up through the limestone, it dissolves it . . . and deposits it on the surface,” Doss explained.

A white trail snaked across the ground near the students, showing where hot water once flowed off a nearby ledge. Springs often become clogged and then dry up as the water begins flowing elsewhere. Trees stood lifeless and bare at the edge of the travertine trail.

The park ranger asked her students about the mystery of the dead trees. Some wondered if the 1988 fires burned them. Others, thinking about experiments that showed acidic spring water in the Norris Geyser Basin, said the culprit might be similar water.

Doss asked the students to look at the base of the trees: The lowest branches were just two or three inches above the travertine.

“We’re not looking at the bottoms of trees,” she said, explaining how travertine deposits rose higher and higher up the tree trunks as the hot springs flowed over the area. “These trees were buried alive.”

The Silverthorne students later would get a peek at the future through a series of small holes that resemble tiny volcanoes or prairie dog burrows in solid rock. They would learn about “ghost trees,” where the wood had weathered away leaving only the travertine mold around their trunks.

The lesson? Rock lasts longer than wood.

But first, Doss told the students to clench their fists and pound on the dirt beneath them. They did, and a hollow sound reverberated from the earth like a giant, muffled bongo drum--evidence of how springs create underground caverns as the water dissolves and transports limestone to the surface.

The students’ last experiment compared the temperature and acidity of a hot spring in the Mammoth area to similar measurements taken in the Norris Geyser Basin.

The hottest temperature measured in Mammoth was 140 degrees, much cooler than the 210-degree reading taken in boiling water in Norris. (Although the standard boiling temperature is 212 degrees, water boils at 199 degrees in Yellowstone because of the high elevation.)

The water temperature in Mammoth decreased as students moved down a small stream and away from the source of the spring.

“You could almost use this as a hot tub,” commented fourth-grade student Michael Ashford after reading a 120-degree temperature. “Maybe way down at the end it would be cooler.”

Fellow student Kyle Johnson used that logic to explain the cooler temperatures found in Mammoth: “We’re farther away from the caldera, and where we were before was right at the edge of the caldera.”

He was right, and ranger Doss explained why. She said the Yellowstone hot spot heats both hot springs in Mammoth and geysers around Norris. Boiling water shoots out of geysers in Norris, but the same water cools down as it travels through a long fault in the earth to get to Mammoth, where it seeps out of the earth.

Silverthorne Elementary was one of several schools to take part in Expedition Yellowstone this spring. The four-day course is in hot demand, and park officials say they cannot meet current requests from elementary schools seeking to take part. Classes are offered only during the spring and fall.

Scott Sperry, media specialist and trip organizer for Silverthorne Elementary, said Yellowstone’s wolves, grizzlies and geysers inspire children and help them understand the value of conservation.

“It’s probably the neatest thing I’ve ever done with kids in the 25 years I’ve been working with grade-school students,” he said.