Ever since geologist Israel Russell first photographed it in 1883, the Lyell Glacier in Yosemite National Park has been closely monitored. The glacier has also shrunken so much that it’s technically no longer a glacier. For The California Sunday Magazine, journalist Daniel Duane follows the life and death of this ancient California ice, to show what glaciers have taught humanity about the Earth’s age and natural cycles, and how that relates to our future on this planet. Duane spends time in the field with Yosemite National Park Geologist Greg Stock, who has studied the Lyell Glacier for so long that, on Stock’s regular glacier visits, Duane compares him to “a man coming home after a long absence, comfortable and eager to catch up.” Seeing his glacier die has left Stock in mourning.

The pleasures of the sublime have a lot to do with my return to the high Sierra year after year, and there is something depressing about the knowledge that I will now have to confront the fragility of those mountains. Once Stock and I reached his dark spot on the Lyell, though, and sat on one of many wet boulders jutting up from the bedrock, and looked out across all those ridges and moraines, I felt the stirrings of something darker still. The end of the Little Ice Age, as punctuated by the death of the Lyell, marks the true end of the entire 2.5-million-year climate regime in which glaciers have advanced and retreated and Homo sapiens have evolved. We don’t know what comes next, except that it will involve a warming climate unlike any that has ever supported human beings.

Back in the early 19th century, and even through Matthes’s work on the Little Ice Age, the study of deep time carried soothing reassurance that old biblical nightmares about catastrophic upheaval were just that, nightmares. The Earth changed and always had changed unimaginably slowly. Now the study of deep time trends toward a different lesson — that Earth changes unimaginably slowly except when it changes suddenly and catastrophically, like right now. Even the driver behind our current warming — abrupt changes to the atmospheric carbon cycle — is not new, having happened at least five times in the past 500 million years. Knowing that human-driven climate change is not so different from dramatic climate changes in our planet’s past offers little comfort when you consider that they all ended badly, with the mass extinction of most living things.

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