Mount Mazama

Around 5677 BC Mazama awoke from its slumber with explosive rhyodacite eruptions on the northern part of the main summit where Llao Rock now resides. Great quantities of pumice and ash were ejected as a large crater was excavated by the explosions. The tephra was carried by prevailing winds to the east and southeast. Associated with this was a pyroclastic flow that was 1.25 mi (2.0 km) wide, 1,200 feet (370 m) thick at its deepest point, and contained 0.25 cu mi (1.0 km³) of material (later, caldera forming subsidence cut the partially filled crater in two, exposing it in cross section—today this is called Llao Rock).

• http://en.wikipedia.org/wiki/Mount Mazama