Beyond four decades of memories and a new route up, Skip Horner left another legacy on Kilimanjaro: 20 pairs of boots for local guides, from The Trail Head in Missoula.

When volcanoes like Alaska’s Mount Spurr erupt, the ash can damage people’s lungs, smother crops and kill animals, and the harm can continue to spread long afterward.

Ash from the 1912 Novarupta eruption periodically hits the west side of Kodiak Island, Larsen Bay and Karluk, roughly 65 ...