Aerial view of Colima Volcano moments after a lava flow on the upper flank of the volcano collapsed; the photograph is tilted slightly (horizon is in upper right). The white plume is rising directly from the summit of the volcano. The tan-colored ash cloud on the volcano's flank (left side in this view) is rising from a pyroclastic flow. The fast-moving pyroclastic flow was caused by the collapse of a thick lava flow that was extruding from the summit area and oozing down the volcano's steep upper cone. When the lava flow collapsed, the hot lava broke apart into fragments ranging in size from boulders to tiny ash particles and swept down the volcano under the influence of gravity to form the pyroclastic flow; the flow reached a maximum distance of 4.5 km from the summit.