Volcanic ash

Volcanic ash

Overview


Volcanic ash consists of small tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....

, which are bits of pulverized rock and glass created by volcanic
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 eruptions, less than 2 millimetre (0.078740157480315 in) in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact with water causing phreatomagmatic eruption
Phreatomagmatic eruption
Phreatomagmatic eruptions are defined as juvenile forming eruptions as a result of interaction between water and magma. They are different from magmatic and phreatic eruptions. The products of phreatomagmatic eruptions contain juvenile clasts, unlike phreatic eruptions, and are the result of...

s, and ejection of entrained particles during steam eruptions causing phreatic eruption
Phreatic eruption
A phreatic eruption, also called a phreatic explosion or ultravulcanian eruption, occurs when rising magma makes contact with ground or surface water. The extreme temperature of the magma causes near-instantaneous evaporation to steam, resulting in an explosion of steam, water, ash, rock, and...

s.
Discussion
Ask a question about 'Volcanic ash'
Start a new discussion about 'Volcanic ash'
Answer questions from other users
Full Discussion Forum
 
Unanswered Questions
Recent Discussions
Encyclopedia


Volcanic ash consists of small tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....

, which are bits of pulverized rock and glass created by volcanic
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 eruptions, less than 2 millimetre (0.078740157480315 in) in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact with water causing phreatomagmatic eruption
Phreatomagmatic eruption
Phreatomagmatic eruptions are defined as juvenile forming eruptions as a result of interaction between water and magma. They are different from magmatic and phreatic eruptions. The products of phreatomagmatic eruptions contain juvenile clasts, unlike phreatic eruptions, and are the result of...

s, and ejection of entrained particles during steam eruptions causing phreatic eruption
Phreatic eruption
A phreatic eruption, also called a phreatic explosion or ultravulcanian eruption, occurs when rising magma makes contact with ground or surface water. The extreme temperature of the magma causes near-instantaneous evaporation to steam, resulting in an explosion of steam, water, ash, rock, and...

s. The violent nature of volcanic eruptions involving steam results in the magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

 and solid rock surrounding the vent being torn into particles of clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...

 to sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

 size. Volcanic ash can lead to breathing problems and malfunctions in machinery, and clouds of it can threaten aircraft and alter weather patterns.

Ash deposited on the ground after an eruption is known as ashfall deposit. Significant accumulations of ashfall can lead to the immediate destruction of most of the local ecosystem, as well the collapse of roofs on man-made structures. Over time, ashfall can lead to the creation of fertile soils. Ashfall can also become cemented together to form a solid rock called tuff
Tuff
Tuff is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. Tuff is sometimes called tufa, particularly when used as construction material, although tufa also refers to a quite different rock. Rock that contains greater than 50% tuff is considered...

. Over geologic time, the ejection of large quantities of ash can produce an ash cone.

Formation


There are three mechanisms of volcanic ash formation:
  1. Gas release under decompression causing magmatic eruptions;
  2. Thermal contraction from chilling on contact with water causing phreatomagmatic eruptions
  3. Ejection of entrained particles during steam eruptions causing phreatic eruptions. The violent nature of volcanic eruptions involving steam results in the magma
    Magma
    Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

     and solid rock surrounding the vent being torn into particles of clay
    Clay
    Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...

     to sand
    Sand
    Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

     size.


If a volcanic eruption occurs beneath glacial ice, cold water from melted ice chills the lava quickly and fragments it into glass, creating small glass particles that get carried into the eruption plume. This can create a glass-rich plume in the upper atmosphere which is particularly hazardous to aircraft.

Composition



The term for any material explosively thrown out from a vent is tephra or pyroclastic debris. Ash terminology is restricted to very fine rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

 and mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

 particles less than 2 millimetre (0.078740157480315 in) in diameter which are ejected from a volcanic vent.
Clast Size Pyroclast Mainly Unconsolidated:

Tephra
Mainly Consolidated:

pyroclastic rock
> 64 mm Bomb, Block Agglomerate Agglomerate, pyroclastic breccia
< 64 mm Lapillus
Lapilli
Lapilli is a size classification term for tephra, which is material that falls out of the air during a volcanic eruption or during some meteorite impacts. Lapilli means "little stones" in Latin. They are in some senses similar to ooids or pisoids in calcareous sediments.By definition lapilli range...

Layer, Lapilli Tephra Lapilli Tuff, Lapillistone
< 2 mm Coarse Ash Coarse Ash Coarse (ash) Tuff
< 0.063 mm Fine Ash Fine Ash Fine (ash) Tuff
Table modified after Heiken and Wohletz, 1985.


Ash is created when solid rock shatters and magma separates into minute particles during explosive volcanic activity. The usually violent nature of an eruption involving steam (phreatic eruption
Phreatic eruption
A phreatic eruption, also called a phreatic explosion or ultravulcanian eruption, occurs when rising magma makes contact with ground or surface water. The extreme temperature of the magma causes near-instantaneous evaporation to steam, resulting in an explosion of steam, water, ash, rock, and...

 or phreatomagmatic eruption
Phreatomagmatic eruption
Phreatomagmatic eruptions are defined as juvenile forming eruptions as a result of interaction between water and magma. They are different from magmatic and phreatic eruptions. The products of phreatomagmatic eruptions contain juvenile clasts, unlike phreatic eruptions, and are the result of...

) results in the magma and solid rock surrounding the vent being torn into particles of clay to sand size.

Spread



The plume that is often seen above an erupting volcano is composed primarily of ash and steam. The very fine particles may be carried for many miles, settling out as a dust-like layer across the landscape. This is known as an ashfall.
If liquid magma is ejected as a spray, the particles will solidify in the air as small fragments of volcanic glass. Unlike the ash that forms from burning wood or other combustible
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

 materials, volcanic ash is hard and abrasive. It does not dissolve in water, and it conducts electricity, especially when it is wet.

Ashfall can become cemented together by heat to form a solid rock called tuff. Ashfall breaks down over time, forming highly fertile soil, which has made many volcanic regions densely cultivated and inhabited despite the inherent dangers.

In 1783, the Laki
Laki
Łąki may refer to the following places in Poland:*Łąki, Lower Silesian Voivodeship *Łąki, West Pomeranian Voivodeship *Łąki, Lublin Voivodeship...

 eruption killed about one-fifth of Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...

's population, and sent a huge toxic cloud of ash and sulphurous gases across Western Europe. In Britain alone, it has been estimated that 23,000 died from the poisoning.

Atmospheric effects


When ash begins to fall during daylight hours, the sky turns hazy and a pale yellow color. The ashfall may become so dense that daylight turns the sky gray to pitch black, with the ash severely restricting visibility and deadening sound. A darkened ash sky lowers temperatures during daylight hours from what would otherwise be expected. Loud thunder, lightning, as well as the strong smell of sulfur accompany an ashfall. If rain accompanies an ashfall, the tiny particles turn into a slurry of slippery mud. Rain and lightning combined with ash can lead to power outages, breakdowns of communication, and disorientation.

Volcanic ash particles have a maximum residence time in the troposphere
Troposphere
The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols....

 of a few weeks. The finest tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....

 particles remain in the stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...

 for only a few months, they have only minor climatic effects, and they can be spread around the world by high-altitude winds. This suspended material contributes to spectacular sunsets. The major climate influence from volcanic eruptions is caused by gaseous sulfur compounds, chiefly sulfur dioxide
Sulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...

, which reacts with OH and water in the stratosphere to create sulfate aerosols with a residence time of about 2–3 years.

Hazards



The most devastating effect of volcanic ash comes from pyroclastic flow
Pyroclastic flow
A pyroclastic flow is a fast-moving current of superheated gas and rock , which reaches speeds moving away from a volcano of up to 700 km/h . The flows normally hug the ground and travel downhill, or spread laterally under gravity...

s. These occur when a volcanic eruption creates an "avalanche" of hot ash, gases, and rocks that flow at high speed down the flanks of the volcano. These flows can be impossible to outrun. They can also be difficult to predict. In many cases prediction is based on the topography of a region, but a valley may fill and overflow. In 1902, the city of St. Pierre in Martinique
Martinique
Martinique is an island in the eastern Caribbean Sea, with a land area of . Like Guadeloupe, it is an overseas region of France, consisting of a single overseas department. To the northwest lies Dominica, to the south St Lucia, and to the southeast Barbados...

 was destroyed by a pyroclastic flow which killed over 29,000 people.

Fluoride poisoning
Fluoride poisoning
In high concentrations, soluble fluoride salts are toxic and skin or eye contact with high concentrations of many fluoride salts is dangerous. Referring to a common salt of fluoride, sodium fluoride , the lethal dose for most adult humans is estimated at 5 to 10 g...

 and death can occur in livestock that graze on ash-covered grass if fluoride is present in high concentrations. Inhaling volcanic ash may cause problems for people whose respiratory system is already compromised by disorders such as asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...

 or emphysema
Emphysema
Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath. In people with emphysema, the tissues necessary to support the physical shape and function of the lungs are destroyed. It is included in a group of diseases called chronic obstructive pulmonary...

. The abrasive texture can cause irritation and scratching of the surface of the eyes. People who wear contact lens
Contact lens
A contact lens, or simply contact, is a lens placed on the eye. They are considered medical devices and can be worn to correct vision, for cosmetic or therapeutic reasons. In 2004, it was estimated that 125 million people use contact lenses worldwide, including 28 to 38 million in the United...

es should wear glasses
Glasses
Glasses, also known as eyeglasses , spectacles or simply specs , are frames bearing lenses worn in front of the eyes. They are normally used for vision correction or eye protection. Safety glasses are a kind of eye protection against flying debris or against visible and near visible light or...

 during an ashfall, to prevent eye damage. Furthermore, the combination of volcanic ash with moisture in the lungs can create a substance akin to liquid cement.

Therefore, people should take caution to filter the air they breathe with a damp cloth or a face mask when facing an ashfall. Ash is very dense, as only 100 millimetres (3.9 in) of ash leads to the collapse of weaker roofs. A fall of 300 millimetres (11.8 in) leads to the death of most vegetation, livestock, the wiping out of aquatic life in nearby lakes and rivers, and unusable roads. Accompanied by rain and lightning, ashfall leads to power outages, prevents communication, and disorients people.

Aviation


According to Dr. Dougal Jerram, an earth scientist at the Centre for Research into Earth Energy Systems
Centre for Research into Earth Energy Systems (CeREES)
The Centre for Research into Earth Energy Systems is a Geo-Energy research centre at Durham University. The centre was formed in January 2006, and since then has won a research income of £1.3M per annum. The current Director of CeREES is Professor Jon Gluyas, co-author of textbook Petroleum...

, University of Durham, UK, "Eruptions which are charged with gas start to froth and expand as they reach the surface. This results in explosive eruptions and this fine ash being sent up into the atmosphere. If it is ejected high enough, the ash can reach the high winds and be dispersed around the globe, for example, from Iceland to Europe. These high winds are exactly where the aeroplanes cruise." Volcanic ash can harm a plane mainly in four ways:

Sandblasting effect


Ash can "blind" pilots by sandblasting the windscreen requiring an instrument landing, damage the fuselage, and coat the plane (KLM Flight 867
KLM Flight 867
On 15 December 1989, KLM Flight 867 en route to Narita International Airport, Tokyo from Amsterdam was descending into Anchorage International Airport, Alaska when all four engines failed...

 and BA Flight 9
British Airways Flight 9
British Airways Flight 9, sometimes referred to by its callsign Speedbird 9 or Jakarta incident, was a scheduled British Airways flight from London Heathrow to Auckland, with stops in Bombay, Madras, Kuala Lumpur, Perth, and Melbourne....

). In addition, the sandblasting effect can damage the landing lights, making their beams diffuse and unable to be projected in the forward direction (BA Flight 9). Propeller
Propeller (aircraft)
Aircraft propellers or airscrews convert rotary motion from piston engines or turboprops to provide propulsive force. They may be fixed or variable pitch. Early aircraft propellers were carved by hand from solid or laminated wood with later propellers being constructed from metal...

-aircraft are also endangered.

Clogging of the plane's sensors


Accumulation of ash can also block an aircraft's pitot tube
Pitot tube
A pitot tube is a pressure measurement instrument used to measure fluid flow velocity. The pitot tube was invented by the French engineer Henri Pitot Ulo in the early 18th century and was modified to its modern form in the mid-19th century by French scientist Henry Darcy...

s. This can lead to failure of the aircraft's air speed indicators.

Electromagnetic wave insulation


Volcanic ash particles are charged
Static electricity
Static electricity refers to the build-up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Static electricity can be contrasted with current electricity, which can be delivered...

 and disturb communication by radio
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...

.

Combustion power failure



Volcanic ash damages machinery. The effect on jet aircraft engines is particularly severe as large amounts of air are sucked in during combustion
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

 operation, posing a great danger to aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 flying near ash clouds. Very fine volcanic ash particles (particularly glass-rich if from an eruption under ice) sucked into a jet engine
Jet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...

 melt at about 1,100 °C, fusing onto the blades and other parts of the turbine (which operates at about 1,400 °C).

Potential effects on the operation of a jet engine include:
  • Volcanic ash particles in substantial quantities can erode and destroy parts or cause jams in rotating machinery.
  • Fooling of the engine temperature sensors (KLM Flight 867).


High concentrations of volcanic gases in an eruption plume can cause other problems that should be distinguished from those caused by ash:
  • Simple lack of oxygen
    Oxygen
    Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

     is given as a probable cause of engine failure (fooling of the air/fuel control).
  • Compressor stall
    Compressor stall
    A compressor stall is a situation of abnormal airflow resulting from a stall of the aerofoils within the compressor of a jet engine. Stall is found in dynamic compressors, particularly axial compressors, as used in jet engines and turbochargers for reciprocating engines.Compressor stalls result in...

     and flameout
    Flameout
    A flameout refers to the failure of a jet engine caused by the extinction of the flame in the combustion chamber. It can be caused by a number of factors, including fuel exhaustion; compressor stall; insufficient oxygen supply; foreign object damage ; severe inclement weather; and mechanical...

     can be another result.


The standard emergency procedure
Emergency procedure
An emergency is a serious, unexpected, often dangerous situation that requires immediate action. The emergency procedure is a plan of actions to be conducted in a certain order or manner, in response to an emergency event.-Need for Emergency Procedures:...

 when jet engines begin to fail had been to increase power, which makes the problem worse. The best procedure is to throttle back the engines, turn on engine and wing anti-ice devices (it helps to avoid compressor and wing stall
Stall (flight)
In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded...

), and to lose height so as to drop below the ash cloud as quickly as possible. The inrush of cold, clean air is usually enough to cool, solidify, and shatter the glass, unclogging the engines.

Occurrences


There are many instances of damage to jet aircraft as a result of an ash encounter. After the Galunggung
Galunggung
Mount Galunggung is an active stratovolcano in West Java, Indonesia, around 80 km southeast of the West Java provincial capital, Bandung...

, Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

 volcanic event in 1982, a British Airways Flight 9
British Airways Flight 9
British Airways Flight 9, sometimes referred to by its callsign Speedbird 9 or Jakarta incident, was a scheduled British Airways flight from London Heathrow to Auckland, with stops in Bombay, Madras, Kuala Lumpur, Perth, and Melbourne....

 flew through an ash cloud; all four engines cut out. The plane descended from 36000 feet (10,972.8 m) to 12000 feet (3,657.6 m), where the engines could be restarted. On December 15, 1989 a KLM
KLM Royal Dutch Airlines
Koninklijke Luchtvaart Maatschappij N.V., operating under the name KLM Royal Dutch Airlines , is the flag carrier airline of the Netherlands and is part of Air France-KLM...

 Boeing 747-400
Boeing 747-400
The Boeing 747-400 is a major development and the best-selling model of the Boeing 747 family of jet airliners. While retaining the four-engine wide-body layout of its predecessors, the 747-400 embodies numerous technological and structural changes to produce a more efficient airframe...

 (Flight 867
KLM Flight 867
On 15 December 1989, KLM Flight 867 en route to Narita International Airport, Tokyo from Amsterdam was descending into Anchorage International Airport, Alaska when all four engines failed...

) flying from Amsterdam Schiphol Airport
Amsterdam Schiphol Airport
Amsterdam Airport Schiphol ) is the Netherlands' main international airport, located 20 minutes southwest of Amsterdam, in the municipality of Haarlemmermeer. The airport's official English name, Amsterdam Airport Schiphol, reflects the original Dutch word order...

 to Anchorage International Airport encountered similar problems near Mount Redoubt (Alaska)
Mount Redoubt (Alaska)
Mount Redoubt, or Redoubt Volcano, is an active stratovolcano in the largely volcanic Aleutian Range of the U.S. state of Alaska. Located in the Chigmit Mountains , the mountain is just west of Cook Inlet, in the Kenai Peninsula Borough about 180 km southwest of Anchorage...

. The damage was 80 million US$; there was 80 kg ash in each turbine; it took 3 months work to repair the plane.

In April 2010, airspace
Airspace
Airspace means the portion of the atmosphere controlled by a country above its territory, including its territorial waters or, more generally, any specific three-dimensional portion of the atmosphere....

 all over Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 was closed
Air travel disruption after the 2010 Eyjafjallajökull eruption
In response to concerns that volcanic ash ejected during the 2010 eruptions of Eyjafjallajökull in Iceland would damage aircraft engines, the controlled airspace of many European countries was closed to instrument flight rules traffic, resulting in the largest air-traffic shut-down since World War II...

—which was unprecedented—due to the presence of volcanic ash in the upper atmosphere from the eruption of the Icelandic volcano Eyjafjallajökull
2010 eruptions of Eyjafjallajökull
The 2010 eruptions of Eyjafjallajökull were volcanic events at Eyjafjöll in Iceland which, although relatively small for volcanic eruptions, caused enormous disruption to air travel across western and northern Europe over an initial period of six days in April 2010. Additional localised disruption...

. On 15 April 2010 the Finnish Air Force
Finnish Air Force
The Finnish Air Force is one of the branches of the Finnish Defence Forces. Its peacetime tasks are airspace surveillance, identification flights, and production of readiness formations for wartime conditions...

 halted training flights when damage was found from volcanic dust ingestion by the engines of one of its Boeing F-18 Hornet fighters. On 22 April 2010 UK RAF Typhoon
Eurofighter Typhoon
The Eurofighter Typhoon is a twin-engine, canard-delta wing, multirole combat aircraft, designed and built by a consortium of three companies: EADS, Alenia Aeronautica and BAE Systems; working through a holding company, Eurofighter GmbH, which was formed in 1986...

 training flights were also temporarily suspended after deposits of volcanic ash were found in a jet's engines.


Aviation risks of flight through downstream ash clouds


A distinction can be made between flight through (or in the immediate vicinity of) an eruption plume, and flight through the so-called affected airspace. Volcanic ash in the immediate vicinity of the eruption plume is of an entirely different particle size range and density to that found in downwind dispersal clouds, which contain only the finest grade of ash. The actual level of ash loading which catastrophically affects normal engine operation has not yet been established, beyond the knowledge that relatively high ash densities must exist for this to happen. Whether this silica-melt risk still remains at the much lower ash densities characteristic of downstream ash clouds is currently unclear.

Detection and avoidance


In June 2010, Easyjet
EasyJet
EasyJet Airline Company Limited is a British airline headquartered at London Luton Airport. It carries more passengers than any other United Kingdom-based airline, operating domestic and international scheduled services on 500 routes between 118 European, North African, and West Asian airports...

 airline company has unveiled a system based on infrared light that it says will allow pilots to detect volcanic ash plumes up to 100 kilometres (62.1 mi) ahead and so safely fly around them. The system is based on 20-year old research by Fred Prata, then at the Australian research organisation CSIRO and now based at the Norwegian Institute for Air Research.

Marine transportation


Similar to aviation, volcanic ash has detrimental effects on marine transportation machinery. However, it poses much less of a hazard—an aircraft encountering an ash plume has engines sucking in huge amounts of air, and cannot stop them until the plume passes, possibly days later.

Advisories concerning ongoing events


Increasing numbers of airplane incidents from atmospheric ash prompted a 1991 aviation industry meeting to decide how best to distribute information about ash events. One solution was the creation of Volcanic Ash Advisory Center
Volcanic Ash Advisory Center
A Volcanic Ash Advisory Center is a group of experts responsible for coordinating and disseminating information on atmospheric volcanic ash clouds that may endanger aviation. As of 2010, there are nine Volcanic Ash Advisory Centers located around the world, each one focusing on a particular...

s. There is one VAAC for each of nine regions of the world. VAACs can issue advisories and serve as liaisons between meteorologists, volcanologists, and the aviation industry.

Further reading


  • U.S. Department of the Interior. U.S. Geological Survey. (1991). First international symposium on volcanic ash and aviation safety : program and abstracts : Seattle, Washington, July 8–12, 1991 [U.S. Geological Survey Circular 1065]. Denver: author.


External links