Entering Haleakala Crater, the enormous mouth of Maui’s largest volcano, in the Hawaiian Islands, feels like an exercise in sensory deprivation. At the crater floor, a desolate expanse of twisted, dried lava reached after a two-hour hike down a trail carved into its wall, the silence is absolute. Not a breath of wind. No passing insects. No bird songs. Then I thought I detected drumming. Was it the ghostly echo of some ancient ritual? No, I finally realized, it was my own heartbeat, thundering in my ears.

In 2008, National Park Service acoustic experts found that the ambient sound levels within Haleakala crater were near the very threshold of human hearing—despite the popularity of the park. Around one million people a year visit the park, many of whom also ascend to its highest point—Haleakala’s 10,023-foot summit—and peer down at the vast field of dried lava below, which, in 1907, the writer and adventurer Jack London called “a workshop of nature still cluttered with the raw beginnings of world-making.”

The now-dormant volcano, which emerged from the Pacific Ocean more than a million years ago, takes up fully three-quarters of Maui’s landmass. Although its interior, whose rim is 7 1/2 miles long and 2 1/2 miles wide, is commonly called a crater, geologists refer to it as an “erosional depression” because it was created not by an eruption but by two valleys merging. Still, there has been frequent volcanic activity on its floor. Carbon dating and Hawaiian oral history suggest that the last eruption occurred between 1480 and 1780, when a cone on the mountain’s southern flank sent lava surging down to La Pérouse Bay, about two miles from Maui’s southernmost tip, near the modern resort town of Wailea.

Only a small number of visitors to Haleakala descend to the crater floor. Those who make the effort, as London did on horseback with his wife, friends and a band of Hawaiian cowboys, find themselves in a strangely beautiful world of britt...