The Latest Slides in the White Mountains
The White Mountains of New Hampshire have once again experienced significant landslides. The most notable recent event occurred on July 10, on the north slope of Cherry Mountain, and was described in Science on July 31. Since then, additional slides have appeared at various locations, with a particularly large one at Waterville.
On August 13, heavy rainfall caused severe flooding in Waterville. Fields and hillsides around Elliot’s Hotel were submerged, and the Mad River rose by twenty to thirty feet. This rainstorm renewed and enlarged the famous slide on the south side of Tripyramid, while a similar slide also appeared on the north side of the same mountain. This northern slide is not easily visible from popular White Mountain viewpoints, except from the distant summit of Mount Washington Turkey Tour Guide.
I had the opportunity to visit both slides on September 10, accompanied by several guests from the hotel. We started with the northern slide, then climbed the north peak of Tripyramid, followed the ridge to the south peak, and finally descended the old southern slide to its base in Beckytown.
The Northern Slide
At the upper end of the northern slide, four smaller slides converge into one. Two of these tributary slides are extremely steep and dangerous to traverse. Each tributary is roughly half a mile long, while the main combined stream extends about one mile. The slide runs entirely through a primitive forest, stopping about half a mile short of Norway Brook. Its lower end is marked by a massive pile of tree stumps and roots. The exposed rocks along the slide are primarily gabbro.
From the north peak of Tripyramid, one can also see movement in slides on the west side of Mount Lowell, formerly called Brickhouse Mountain, indicating that this has been an active season for landslides in the White Mountains The Berlin Congress and the Eastern Question.
The Old Tripyramid Slide
The first large slide on Tripyramid occurred on October 4, 1869, during a severe rainstorm that caused $1–2 million in damage to New Hampshire. The initial steep slope extended three-fourths of a mile, then the slide bent at a right angle and continued more than two miles to Beckytown, where deposited trees marked the slide’s end.
The new slide is larger at its origin, covering nearly three times the area of the original slope. However, it was less destructive below the bend because bushes had grown at the old base over the sixteen years since the first slide. Not all vegetation was removed, which limited the slide’s lower reach compared to the 1869 event.
Comparison with Other Slides
For perspective, the flood that moved a boulder from the Flume in Lincoln (Franconia) three years ago appears to have been more powerful than any of this season’s slides. These continuous events remind us that the White Mountains are geologically active, and their steep slopes combined with heavy rains can produce dramatic and sometimes dangerous landslides.
C. H. Hitchcock
