John Muir first visited Yosemite Valley in 1868, four years after Abraham Lincoln signed the Yosemite Grant protecting the land for public use. Muir wrote beautifully about the landscape, and became an important advocate for natural parks. But he was also scientifically minded, and Yosemite’s glaciers fascinated him.

Geomorphologist Denny Capps describes how Muir measured the movement of Maclure Glacier using pine stakes, horsehair, and a plumb bob in 1872. Muir concluded that Yosemite owed its existence to glacial movement, and by 1890, Yosemite was a national park. To Capp, this wasn’t merely coincidence. He argues that science helped establish national parks, and parks in turn enabled extensive scientific research.

Glaciology was relatively new when Muir arrived at Yosemite. Swiss geologist Louis Agassiz had studied European glaciers in the mid-nineteenth century before emigrating to the United States. His work influenced University of Wisconsin’s Professor of Natural Sciences Ezra Carr, who taught John Muir. Capp explains that Agassiz himself would later describe Muir as “the first man I have ever found who has any adequate concept of glacial action.”

Muir’s theories “came together in a powerful package that thrust glaciers and protected lands into the public eye and imagination,” Capp writes. Then, in the late 1890s, US Geological Survey (USGS) geologist Israel Russell traversed the US mapping and photographing glaciers. In spectacular imagery, Russell “documented the presence of present-day glaciers in Yosemite, Glacier, Grand Tetons, and Mount Rainier national parks,” Capp writes.

By 1916, when the Organic Act created the National Park Service (NPS), there were twelve national parks. Of these, Capp points out, two-thirds had glacial pasts, and four held existing glaciers. Glaciological research has continued at these parks for decades.

A similar relationship exists between volcanology and parks, according to Laura Walkup and Thomas Casadevall of the USGS and Vincent Santucci of the NPS. Yellowstone became the first national park in 1872, and over time, scientists have pieced together the story of the volcanic field powering the park’s famous geothermal features. One eruption millions of years ago sent ash flying as far as Canada and Mexico. These theories required decades of sustained research, Walkup et al. explain.

“National parks are natural laboratories for scientific study,” they write, in part because they enable this type of long-term research. At Hawai‘i Volcanoes National Park, for example, geologist Thomas Jaggar helped establish a volcano observatory in 1912. The observatory continues to monitor volcanoes like Kīlauea, which erupted “nearly incessantly” between 1983 and 2018 and has recently resumed eruptions.

Scientific research in national parks has great practical import. Glaciology and volcanology both help in keeping local communities safe, and in understanding climate change. At Mount Rainier, a volcano home to substantial glaciers, these sciences come together in spectacular fashion. Walkup et al. describe formations that emerged as “lavas solidified against the glaciers that formerly filled the flanking valleys to depths of hundreds of meters.”

Muir climbed Rainier in 1888. He described looking out from the summit over a landscape shaped by ice and fire, filled with “black, interminable forests and white volcanic cones in glorious array.”