Camas Prairie

Geologists have since answered part of the sign's question. The rocks of the Kamiah Buttes are now mapped as their own unit, the Kamiah volcanics, a mix of basalt, andesite and rhyolite dated to about 32 million years ago, in the Oligocene: younger than the sign's forty million and younger than the Challis rocks they were compared with, but still far older than the lava around them. That lava, the Columbia River Basalt, poured out between about 16.7 and 5.5 million years ago from fissures fed by the plume that now lies under Yellowstone.

What the plaque says

Camas Prairie Most of Camas Prairie's wind blown soil rests upon Columbia River lava flows. Coming from a series of widespread eruptions, they covered older, eroded granite rocks here some 6 to 17 million years ago. Some earlier volcanic extrusions, including Kamiah Buttes (between which this highway passes) rise above those Camas Prairie lavas. Perhaps older than 40 million years, they resemble volcanic rocks from Challis, in south central Idaho, rather than newer lava from farther west. Geologists still are studying how these buttes are related to similar formations elsewhere in Idaho. 372

Where it stands

Worth the stop nearby

• Heart of the Monster — 9.4 mi
  Where the Nimiipuu say their story begins: Coyote, a monster, and the heart he tore loose, still on the Clearwater's bank.
• Weippe Prairie — 19 mi
  Where the Nimiipuu decided what to do with Clark's starving men, and fed them camas until they were sick.
• White Bird Battlefield — 25 mi
  Six Nimiipuu men rode out under a white flag. A shot came from the soldiers' side, and the Nez Perce War began.

More markers nearby

• Lewis and Clark — 7.5 mi
• Long Camp — 9.7 mi
• Asa Smith Mission — 9.7 mi
• Nez Perce War — 10 mi