Mountains on the Move

The slide this panel describes left a visible mark. Down the valley, along about sixty miles of the range, the Bitterroots' eastern face rises in smooth slopes of twenty to thirty degrees, unlike the jagged peaks behind. That face is mylonite, rock sheared into platy, streaky layers over a thousand feet thick along the fault the Sapphire block rode, its streaks pointing just south of east, the way the block went. A younger fault along the same front has moved within the last two and a half million years; the state geological survey is studying its earthquake hazard.

Where it stands

Worth the stop nearby

• Big Hole National Battlefield — 21 mi
  The government marked this ground for its soldiers in 1883 and left the Nimiipuu camp outside the line until the 1960s.

More markers nearby

• First Impressions — steps away
• Survival — steps away
• The Great Clearing — steps away
• Ross' Hole — steps away