Global Volcanism Program | Image GVP-04342
A record of the November 13, 1985 eruption of Nevado de Ruiz was preserved in ice-rich levees of pyroclastic flows. This photo, taken a month later, shows parallel-bedded pyroclastic-surge deposits, composed of snow grains and tephra, which were deposited over a pre-existing surface of clear, coarsely crystalline ice at the bottom of the photo. The surge layers are overlain at the top by coarser-grained pyroclastic-flow deposits. The clast of glacial ice (located left of the upper part of the ice axe) was scoured and incorporated into the pyroclastic flow.
Photo by Tom Pierson, 1985 (U.S. Geological Survey).