In the ruined shell of Mt. Newberry, an easy nature trail tours the freshest lave flow in Central Oregon, a hill of shiny black obsidian glass.  If you'd like to leave the tourists behind, hike a tougher trail around the obsidian flow to the desert of Pumice Flat, and up to the views atop cliff-edged Paulina Peak.

The Newberry Volcano is the latest protrusion of a geologic "hot spot" that's been moving westward from Idaho for 10 million years, leaving a string of lava flows and volcanic buttes in its wake.  Geologists theorize that North America's shearing collision with the Pacific plate has been stretching Oregon diagonally, and lava has been leaking through the cracks.

All that lava has made Newberry the state's most massive volcano, measured by volume.  Countless thin basalt lava flows have built up its 25-mile-wide shield-shaped bulk over the past half million years.  Like many aging volcanoes, Mt. Newberry's eruptions gradually contained more silica, making the lava thicker, glassier, and more explosive.  The entire mountaintop has blown up in Crater Lake fashion at least twice, leaving a gaping, 6-mile-wide caldera.  The giant lake that once filled that caldera has since been spilt in two by lava flows.  The largest of these flows, the Big Obsidian Flow, poured more than a square mile of black glass into the caldera just 1300 years ago.    . . .

This chapter is an excerpt from 100 Hikes: Eastern Oregon