A lahar ( /ˈlɑːhɑːr/, from Javanese: ꦮ꧀ꦭꦲꦂ, romanized: wlahar) 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.
Lahars are extremely destructive: they can flow tens of metres per second (22 mph or more), they have been known to be up to 140 metres (460 ft) deep, and large flows tend to destroy any structures in their path. Notable lahars include those at Mount Pinatubo and Nevado del Ruiz, the latter of which covered entire towns and killed thousands of people.
A lahar is a volcanic mudflow or debris flow. Lahars have the consistency, viscosity and approximate density of wet concrete: fluid when moving, solid at rest. Lahars can be huge. The Osceola Lahar produced by Mount Rainier (Washington) some 5600 years ago resulted in a wall of mud 140 metres (460 ft) deep in the White River canyon, which covered an area of over 330 square kilometres (130 sq mi), for a total volume of 2.3 cubic kilometres (0.55 cu mi).
A lahar of sufficient size and intensity can erase virtually any structure in its path, and is capable of carving its own pathway, making the prediction of its course difficult. Conversely, a lahar quickly loses force when it leaves the channel of its flow: even frail huts may remain standing, while at the same time being buried to the roof line in mud. A lahar's viscosity decreases with time, and can be further thinned by rain, but it nevertheless solidifies quickly when coming to a stop.
Lahars vary in size and speed. Small lahars less than a few metres wide and several centimetres deep may flow a few metres per second. Large lahars hundreds of metres wide and tens of metres deep can flow several tens of metres per second (22 mph or more): much too fast for people to outrun. With the potential to flow at speeds up to 100 kilometres per hour (60 mph), and flow distances of more than 300 kilometres (190 mi), a lahar can cause catastrophic destruction in its path.
Lahars from the 1985 Nevado del Ruiz eruption in Colombia caused the Armero tragedy, which killed an estimated 23,000 people, when the city of Armero was buried under 5 metres (16 ft) of mud and debris. A lahar caused New Zealand's Tangiwai disaster, where 151 people died after a Christmas Eve express train fell into the Whangaehu River in 1953. Lahars have been responsible for 17% of volcano-related deaths between 1783 and 1997.
Lahars have several possible causes:
In particular, although lahars are typically associated with the effects of volcanic activity, lahars can occur even without any current volcanic activity, as long as the conditions are right to cause the collapse and movement of mud originating from existing volcanic ash deposits.
Several mountains in the world, including Mount Rainier in the United States, Mount Ruapehu in New Zealand, Merapi and Galunggung in Indonesia, are considered particularly dangerous due to the risk of lahars. Several towns in the Puyallup River valley in Washington state, including Orting, are built on top of lahar deposits that are only about 500 years old. Lahars are predicted to flow through the valley every 500 to 1,000 years, so Orting, Sumner, Puyallup, Fife, and the Port of Tacoma face considerable risk. The USGS has set up lahar warning sirens in Pierce County, Washington, so that people can flee an approaching debris flow in the event of a Mount Rainier eruption.
A lahar warning system has been set up at Mount Ruapehu by the New Zealand Department of Conservation and hailed as a success after it successfully alerted officials to an impending lahar on 18 March 2007.
Since mid-June 1991, when violent eruptions triggered Mount Pinatubo's first lahars in 500 years, a system to monitor and warn of lahars has been in operation. Radio-telemetered rain gauges provide data on rainfall in lahar source regions, acoustic flow monitors on stream banks detect ground vibration as lahars pass, and manned watchpoints further confirm that lahars are rushing down Pinatubo's slopes. This system has enabled warnings to be sounded for most but not all major lahars at Pinatubo, saving hundreds of lives. Physical preventative measures by the Philippine government were not adequate to stop over 20 feet (6.1 m) of mud from flooding many villages around Mount Pinatubo from 1992 through 1998.
Scientists and governments try to identify areas with a high risk of lahars based on historical events and computer models. Volcano scientists play a critical role in effective hazard education by informing officials and the public about realistic hazard probabilities and scenarios (including potential magnitude, timing, and impacts); by helping evaluate the effectiveness of proposed risk-reduction strategies; by helping promote acceptance of (and confidence in) hazards information through participatory engagement with officials and vulnerable communities as partners in risk reduction efforts; and by communicating with emergency managers during extreme events. An example of such a model is TITAN2D. These models are directed towards future planning: identifying low-risk regions to place community buildings, discovering how to mitigate lahars with dams, and constructing evacuation plans.
In 1985, the volcano Nevado del Ruiz erupted in central Colombia. As pyroclastic flows erupted from the volcano's crater, they melted the mountain's glaciers, sending four enormous lahars down its slopes at 60 kilometers per hour (37 miles per hour). The lahars picked up speed in gullies and coursed into the six major rivers at the base of the volcano; they engulfed the town of Armero, killing more than 20,000 of its almost 29,000 inhabitants.
Casualties in other towns, particularly Chinchiná, brought the overall death toll to 23,000. Footage and photographs of Omayra Sánchez, a young victim of the tragedy, were published around the world. Other photographs of the lahars and the impact of the disaster captured attention worldwide and led to controversy over the degree to which the Colombian government was responsible for the disaster.
The 1991 eruption of Mount Pinatubo caused lahars: the first eruption itself killed six people, but the lahar killed more than 1500. The eye of Typhoon Yunya passed over the volcano during its eruption on June 15, 1991. The rain from the typhoon triggered the flow of volcanic ash, boulders, and water down the rivers surrounding the volcano. In Pampanga, Angeles City and neighbouring cities and towns were damaged by the volcano's lahar when Sapang Balen Creek and the Abacan River became the channels for the mudflows and carried it to the heart of the city and surrounding areas.
Over 6 metres (20 ft) of mud inundated and damaged the towns of Castillejos, San Marcelino and Botolan in Zambales, Porac and Mabalacat City in Pampanga, Tarlac City, Capas, Concepcion and Bamban in Tarlac. The lahar in the Sacobia-Bamban River scoured all structures in its path, including the bridges and dikes by the Parua River in Concepcion. The Tarlac River in Tarlac City was inundated by over 6 metres (20 ft) of lahar, causing the river to lose the ability to hold water.
On the morning of October 1, 1995, pyroclastic material which clung to the slopes of Pinatubo and surrounding mountains rushed down because of heavy rain, and turned into an 8-metre (25 ft) lahar. This mudflow killed hundreds of people in Barangay Cabalantian in Bacolor. The Philippine government under President Fidel V. Ramos ordered the construction of the FVR Mega Dike in an attempt to protect people from further mudflows.
Another typhoon-caused lahar hit the Philippines in 2006; see Typhoon Reming.
The Armero tragedy (Spanish: Tragedia de Armero [tɾaˈxeðja ðe aɾˈmeɾo]) was one of the major consequences of the eruption of the Nevado del Ruiz stratovolcano in Tolima, Colombia, on November 13, 1985. After 69 years of dormancy, the volcano's eruption caught nearby towns unaware, even though the government had received warnings from multiple volcanological organizations to evacuate the area after the detection of volcanic activity two months earlier.As pyroclastic flows erupted from the volcano's crater, they melted the mountain's glaciers, sending four enormous lahars (volcanically induced mudflows, landslides, and debris flows) down its slopes at 50 kilometers per hour (30 miles per hour). The lahars picked up speed in gullies and engulfed the town of Armero, killing more than 20,000 of its almost 29,000 inhabitants. Casualties in other towns, particularly Chinchiná, brought the overall death toll to 23,000. Footage and photographs of Omayra Sánchez, a young victim of the tragedy, were published around the world. Other photographs of the lahars and the impact of the disaster captured attention worldwide and led to controversy over the degree to which the Colombian government was responsible for the disaster. A banner at a mass funeral in Ibagué read, "The volcano didn't kill 22,000 people. The government killed them."
The relief efforts were hindered by the composition of the mud, which made it nearly impossible to move through without becoming stuck. By the time relief workers reached Armero twelve hours after the eruption, many of the victims with serious injuries were dead. The relief workers were horrified by the landscape of fallen trees, disfigured human bodies, and piles of debris from entire houses. This was the second-deadliest volcanic disaster of the 20th century, surpassed only by the 1902 eruption of Mount Pelée, and is the fourth-deadliest volcanic event recorded since 1500 AD. The event was a foreseeable catastrophe exacerbated by the populace's unawareness of the volcano's destructive history; geologists and other experts had warned authorities and media outlets about the danger over the weeks and days leading up to the eruption. Hazard maps for the vicinity were prepared, but poorly distributed. On the day of the eruption, several evacuation attempts were made, but a severe storm restricted communications. Many victims stayed in their houses as they had been instructed, believing that the eruption had ended. The noise from the storm may have prevented many from hearing the sounds of the eruption until it was too late.
Nevado del Ruiz has erupted several times since the disaster, and continues to threaten up to 500,000 people living along the Combeima, Chinchiná, Coello-Toche, and Guali river valleys. A lahar (or group of lahars) similar in size to the 1985 event might travel as far as 100 kilometres (60 mi) from the volcano, and could be triggered by a small eruption. To counter this threat, the Colombian government established a specialized office which promotes awareness of natural threats. The United States Geological Survey also created the Volcano Disaster Assistance Program and the Volcano Crisis Assistance Team, which evacuated roughly 75,000 people from the area around Mount Pinatubo before its 1991 eruption. In 1988, three years after the eruption, Dr. Stanley Williams of Louisiana State University stated that, "With the possible exception of Mount St. Helens in the state of Washington, no other volcano in the Western Hemisphere is being watched so elaborately" as Nevado del Ruiz. Additionally, many of Colombia's cities have programs to raise awareness of natural disaster planning programs which have helped save lives in natural disasters. Near Nevado del Ruiz in particular, locals have become wary of volcanic activity: when the volcano erupted in 1989, more than 2,300 people living around it were evacuated.Ashnan
Ashnan, also known as Ezina or Ezina-Kusu, was the goddess of grain in Mesopotamia. She and her brother Lahar, both children of Enlil, were created by the gods to provide the Annunaki with food, but when the heavenly creatures were found unable to make use of their products, humankind was created to provide an outlet for their services.Bhind district
Bhind District is a district in the Chambal division of the Indian state of Madhya Pradesh. The town of Bhind is the district headquarters.
Bhind District is situated in Chambal region in the northwest of the state. The geographical coordinates of the district are latitude 26°36' N and longitude 78°46' E. It is bounded by Agra, Etawah, Jalaun and Jhansi districts of Uttar Pradesh state to the north and the east, and the Madhya Pradesh districts of Datia to the south, Gwalior to the southwest, and Morena to the west. The geography of the district is characterised by uneven ravines, plain fertile fields and scanty forests. The total area of the district is 4,459 km2.
The soil of Bhind is very fertile and is drained by the Chambal, Kali Sind, Kunwari or Kwari, Pahuj and Baisali rivers and by an extensive canal system. Formerly there were four tehsils, Bhind, Mehgaon, Gohad and Lahar, but at present there are nine tehsils: Bhind, Ater, Gormi,Mau, Mehgaon, Gohad, Lahar, Mihona, and Raun. The district is part of the Chambal Division.Debris flow
Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generally have bulk densities comparable to those of rock avalanches and other types of landslides (roughly 2000 kilograms per cubic meter), but owing to widespread sediment liquefaction caused by high pore-fluid pressures, they can flow almost as fluidly as water. Debris flows descending steep channels commonly attain speeds that surpass 10 m/s (36 km/h), although some large flows can reach speeds that are much greater. Debris flows with volumes ranging up to about 100,000 cubic meters occur frequently in mountainous regions worldwide. The largest prehistoric flows have had volumes exceeding 1 billion cubic meters (i.e., 1 cubic kilometer). As a result of their high sediment concentrations and mobility, debris flows can be very destructive.
Notable debris-flow disasters of the twentieth century involved more than 20,000 fatalities in Armero, Colombia in 1985 and tens of thousands in Vargas State, Venezuela in 1999.Eastern Ruapehu Lahar Alarm and Warning System
The Eastern Ruapehu Lahar Alarm and Warning System, or ERLAWS, is a lahar warning system that was installed on Mount Ruapehu, New Zealand following volcanic eruptions in 1995–1996. The system successfully detected and warned of an imminent lahar in March 2007. The system is being expanded to detect the wider range of lahar threats now expected on Ruapehu.Hal Lahar
Harold Wade Lahar (July 14, 1919 – October 20, 2003) was an American football player and coach. He served as the head football coach at Colgate University (1952 to 1956 and 1962 to 1967) and the University of Houston (1957 to 1961).
Lahar was born in Durant, Oklahoma and attended Central High School in Oklahoma City. He later was an All-Big Six Conference guard for the Oklahoma Sooners under coach Tom Stidham. Lahar was selected 79th overall in the 1941 NFL Draft by the Chicago Bears, where he spent the 1941 NFL season before serving in the United States Navy in the South Pacific during World War II.
After leaving the service as a Lieutenant (junior grade) in 1945, Lahar played for the Buffalo Bills of the All-America Football Conference from 1946 to 1948 before beginning his college coaching career as an assistant under Otis Douglas at the University of Arkansas in 1950. In 1952, he became the 25th head coach at Colgate University in Hamilton, New York. In 1957, he succeeded Bill Meek at the University of Houston, where he spent five years, before returning to Colgate in 1962, making him the first man to return to a Division I head-coaching job after leaving for another school. Following the 1967 season, Lahar retired from coaching and served as athletic director at Colgate. His overall coaching record at Colgate was 53–40–8.
Lahar was also assistant commissioner of the Southwest Conference. He worked at the now-defunct SWC from 1973 until his retirement in 1983. Upon his death in 2003, Lahar was buried in the Dallas-Fort Worth National Cemetery.Kandovan, Osku
Kandovan (Persian: كندوان, also romanized as Kandovān and Kandavān; also known as Kanvān) is an ancient village in Sahand Rural District in the Central District of Osku County, East Azerbaijan Province, northwestern Iran. It is situated in the foothills of Mount Sahand, near the city of Osku.
The village exemplifies manmade cliff dwellings which are still inhabited. The troglodyte homes, excavated inside volcanic rocks and tuffs similar to dwellings in the Turkish region of Cappadocia, are locally called Karaan. Karaans were cut into the lahars of Mount Sahand. The cone form of the houses is the result of lahar flow consisting of porous, round and angular pumice together with other volcanic particles that were positioned in a grey, acidic matrix. After the eruption of Sahand, these materials were naturally moved and formed the rocks of Kandovan. Around the village the thickness of this formation exceeds 100 metres (330 ft) and with time, due to water erosion, the cone-shaped cliffs were formed.
At the 2006 census, the village population was 601, in 168 families.Lahar, India
Lahar is a town and a Nagar Panchayat in Bhind district in the Indian state of Madhya Pradesh.Lahar (Vidhan Sabha constituency)
Lahar Vidhan Sabha constituency is one of the 230 Vidhan Sabha (Legislative Assembly) constituencies of Madhya Pradesh state in central India. This constituency came into existence in 1951, as one of the 79 Vidhan Sabha constituencies of the erstwhile Madhya Bharat state.Lahar (god)
Lahar was the Sumerian cattle-god or goddess sent by Enlil and Enki from the sky down to earth in order to make abundant its cattle. He is the brother of Ashnan. Lahar, along with his sister, was created in the creation chamber of the gods so the Anunnaki might have food and clothes.Mapanuepe Lake
Mapanuepe Lake is a freshwater lake located in the province of Zambales in the Philippines. The lake was created after the cataclysmic eruption of Mount Pinatubo in 1991. Lahars following the eruption blocked the drainage of Mapanuepe River, south of the volcano, flooding Mapanuepe Valley together with its settlements. Only the steeple of the church protruding out of the water remained on one of the villages.Mount Rainier
Mount Rainier (pronounced: ), also known as Tahoma or Tacoma, is a large active stratovolcano in Cascadia located 59 miles (95 km) south-southeast of Seattle, in Mount Rainier National Park. With a summit elevation of 14,411 ft (4,392 m), it is the highest mountain in the U.S. state of Washington, and of the Cascade Range of the Pacific Northwest, the most topographically prominent mountain in the contiguous United States, and the tallest in the Cascade Volcanic Arc.
Mt. Rainier is considered one of the most dangerous volcanoes in the world, and it is on the Decade Volcano list. Because of its large amount of glacial ice, Mt. Rainier could produce massive lahars that could threaten the entire Puyallup River valley. "About 80,000 people and their homes are at risk in Mount Rainier’s lahar-hazard zones."Mount Rainier Volcano Lahar Warning System
The Mount Rainier Volcano Lahar Warning System consists of two separate components, operating in tandem: Acoustic Flow Monitors (AFM) and the All Hazard Alert Broadcast (AHAB) sirens. The AFM system was developed by the United States Geological Survey (USGS) in 1998 and is now maintained by Pierce County Emergency Management. The purpose of the warning system is to assist in the evacuation of residents in the river valleys around Mount Rainier, a volcano in Washington, in the event of a lahar. Pierce County works in partnership with the USGS, the Pacific Northwest Seismic Network (PNSN), Washington Military Department's Emergency Management Division, and South Sound 9-1-1 to monitor and operate the system.Mount Ruapehu
Mount Ruapehu is an active stratovolcano at the southern end of the Taupo Volcanic Zone in New Zealand. It is 23 kilometres (14 mi) northeast of Ohakune and 23 km (14 mi) southwest of the southern shore of Lake Taupo, within Tongariro National Park. The North Island's major ski resorts and only glaciers are on its slopes.
Ruapehu, the largest active volcano in New Zealand, is the highest point on the North Island and has three major peaks: Tahurangi (2,797 m), Te Heuheu (2,755 m) and Paretetaitonga (2,751 m). The deep, active crater is between the peaks and fills with water between major eruptions, being known as Crater Lake (Māori: Te Wai ā-moe).Nevado del Ruiz
The Nevado del Ruiz (Spanish pronunciation: [neβaðo ðel ˈrwis]), also known as La Mesa de Herveo (English: Mesa of Herveo, the name of the nearby town) is a volcano located on the border of the departments of Caldas and Tolima in Colombia, about 129 kilometers (80 mi) west of the capital city Bogotá. It is a stratovolcano composed of many layers of lava alternating with hardened volcanic ash and other pyroclastic rocks. Volcanic activity at Nevado del Ruiz began about two million years ago, since the Early Pleistocene or Late Pliocene, with three major eruptive periods. The current volcanic cone formed during the present eruptive period, which began 150 thousand years ago.
The volcano usually generates Vulcanian to Plinian eruptions, which produce swift-moving currents of hot gas and rock called pyroclastic flows. These eruptions often cause massive lahars (mud and debris flows), which pose a threat to human life and the environment. The impact of such an eruption is increased as the hot gas and lava melt the mountain's snowcap, adding large quantities of water to the flow. On November 13, 1985, a small eruption produced an enormous lahar that buried and destroyed the town of Armero in Tolima, causing an estimated 25,000 deaths. This event later became known as the Armero tragedy—the deadliest lahar in recorded history. Similar but less deadly incidents occurred in 1595 and 1845, consisting of a small explosive eruption followed by a large lahar.
The volcano is part of Los Nevados National Natural Park, which also contains several other volcanoes. The summit of Nevado del Ruiz is covered by large glaciers. The volcano continues to pose a threat to the nearby towns and villages, and it is estimated that up to 500,000 people could be at risk from lahars from future eruptions.
Today, the Nevado del Ruiz volcano is constantly monitored by the Volcanic and Seismic Observatory of Manizales.Pucón
Pucón (Mapudungun: "entrance to the cordillera") is a Chilean city and commune administered by the municipality of Pucón. It is located in the Province of Cautín, Araucanía Region, 100 km to the southeast of Temuco and 780 km to the south of Santiago. It is on the eastern shore of Lake Villarrica, and Villarrica volcano is located roughly 17 km to the south.
Pucón's location by a lake and volcano, along with its relatively stable climate, especially in summer, make it a popular destination for tourists. It offers a variety of sports and activities for tourists, including water skiing, snow skiing, backpacking, white water rafting and kayaking, horse back riding, natural hot springs, zip line rides, skydiving and guided ascents of Villarrica volcano.San Guillermo Parish Church
San Guillermo Parish Church is named after San Guillermo, the patron saint of Bacolor, Pampanga, Philippines, where the church is erected. The church was originally constructed by the Augustinian Friars in 1576 – also the town's founding – with Fr. Diego De Ochoa, OSA, as the town's first parish priest. Having been installed as such two years after.
In 1880, the church was destroyed by an earthquake only to be rebuilt by Fr. Eugenio Alvarez in 1886. On September 3, 1995, lahar flow from the slopes of Mount Pinatubo which erupted into the world's notice on June 15, 1991, buried the church at half its 12-m height prompting its more than 50,000 town residents to evacuate to safer grounds in resettlement areas. Near the façade of the parish church is a museum which contains the history of the church. It also contains paintings of the Pinatubo eruption in 1991.Stratovolcano
A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava, tephra, pumice and ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity. The magma forming this lava is often felsic, having high-to-intermediate levels of silica (as in rhyolite, dacite, or andesite), with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows are uncommon, but have travelled as far as 15 km (9.3 mi).Stratovolcanoes are sometimes called "composite volcanoes" because of their composite stratified structure built up from sequential outpourings of erupted materials. They are among the most common types of volcanoes, in contrast to the less common shield volcanoes. Two famous examples of stratovolcanoes are Krakatoa in Indonesia, known for its catastrophic eruption in 1883 and Vesuvius in Italy, whose catastrophic eruption in AD 79 ruined the Roman cities of Pompeii and Herculaneum. Both eruptions claimed thousands of lives. In modern times, Mount Saint Helens and Mount Pinatubo have erupted catastrophically, with fewer deaths.
The possible existence of stratovolcanoes on other terrestrial bodies of the Solar System has not been conclusively demonstrated. The one feasible exception is the existence of some isolated massifs on Mars, for example the Zephyria Tholus.Tangiwai disaster
The Tangiwai disaster occurred at 10:21 p.m. on 24 December 1953 when the Whangaehu River bridge collapsed beneath Wellington-to-Auckland express passenger train No. 626 at Tangiwai, in the central North Island of New Zealand. The locomotive and first six carriages derailed into the river, killing 151 people. The subsequent Board of Inquiry found that the accident was caused by the collapse of the tephra dam holding back nearby Mount Ruapehu's crater lake, creating a large lahar in the Whangaehu River, which destroyed one of the bridge piers at Tangiwai only minutes before the train reached the bridge. The disaster remains New Zealand's worst rail accident.