A lahar is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley.
A lahar travels down a river valley in Guatemala near the Santa Maria volcano, 1989
Excavated 9th century Sambisari Hindu temple near Yogyakarta in Java, Indonesia. The temple was buried 6.5 metres under the lahar volcanic debris accumulated from centuries of Mount Merapi eruptions.
Mudline left behind on trees on the banks of the Muddy River after the 1980 eruption of Mount St. Helens showing the height of the lahar
The aftermath of a lahar from the 1982 eruption of Galunggung, Indonesia
Mount Pinatubo is an active stratovolcano in the Zambales Mountains, located on the tripoint boundary of the Philippine provinces of Zambales, Tarlac and Pampanga, all in Central Luzon on the northern island of Luzon. Its eruptive history was unknown to most before the pre-eruption volcanic activity of early 1991. Pinatubo was heavily eroded and obscured from view by dense forests which supported a population of several thousand indigenous Aetas.
Mount Pinatubo crater lake in 2012
Aerial view of Mount Pinatubo before the 1991 eruption, March 1933
Pinatubo in April 1991, approximately two months before the eruption.
The eruption column of Mount Pinatubo on June 12, 1991, three days before the climactic eruption