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Indians Last Leap

Geologic Rumblings Created Indian’s Last Leap

By Kevin McKeon, Director of the Mousam Way Land Trust

Arguably Sanford’s most beautiful footpath along its extensive trail system, Mousam Way North offers parking at the Stanley Road trailhead, from which a 900-foot, well-marked trail leads to Indian’s Last Leap. We’ve heard many variations of the legend, but this is the geologic origin story.

About 395 million years ago, a huge ocean covered the land, from which a clay-rich sediment settled onto the ocean floor. Over millions of years, this became about a mile thick. The resultant pressure and heat from the thickness converted this sediment to slate. Heat and pressure from a continental collision crumpled and folded the slate, forming a mica schist. Then, about 9-12 miles beneath the bedrock of the time, molten magma intruded into this schist, cooling into granite. At that time, Indians Last Leap was 9-12 miles underground.

A long uninterrupted period of erosion, followed by several glacial episodes, stripped away much of the bedrock, exposing the granite at Indian’s Last Leap, and forming a granite ridge which spans the valley of today’s Mousam River. As the bedrock eroded away, the release of the pressure and heat of the miles-thick bedrock created cracks in the granite. Then, the erosive actions from the most recent glacier both smoothed the top of the Leap and plucked chunks of the cracked granite from the southern side, leaving the sharp-edged boulders of today.

As the glacier melted, a turbulent cascading falls evolved over the granite rocks. Also, a crack that formed earlier on the granite ridge allowed the torrential flow of constricted sand and rock-infused melt water. This erosive power widened the crack into a trough and then into a gorge. Eventually, the bed of the gorge was eroded below the top of the cascading falls, with the gorge finally accepting the full flow of the melt water and forming (what would become) the Mousam River.

“It must have been quite a sight some 14,000 years ago when water cascaded over the steps and flowed in a plume from the crevice,” says Gordon “Bud” Johnston.

Adapted from The Formation of Indian’s Last Leap by Gordon “Bud” Johnston

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