Eruption column

Last updated
Eruption column over Mount Pinatubo in the Philippines, 1991 Pinatubo ash plume 910612.jpg
Eruption column over Mount Pinatubo in the Philippines, 1991

An eruption column or eruption plume is a cloud of super-heated ash and tephra suspended in gases emitted during an explosive volcanic eruption. The volcanic materials form a vertical column or plume that may rise many kilometers into the air above the vent of the volcano. In the most explosive eruptions, the eruption column may rise over 40 km (25 mi), penetrating the stratosphere. Stratospheric injection of aerosols by volcanoes is a major cause of short-term climate change.


A common occurrence in explosive eruptions is column collapse when the eruption column is or becomes too dense to be lifted high into the sky by air convection, and instead falls down the slopes of the volcano to form pyroclastic flows or surges (although the latter is less dense). On some occasions, if the material isn't dense enough to fall, it may create pyrocumulonimbus clouds.


Eruption columns form in explosive volcanic activity, when the high concentration of volatile materials in the rising magma causes it to be disrupted into fine volcanic ash and coarser tephra. The ash and tephra are ejected at speeds of several hundred metres per second, and can rise rapidly to heights of several kilometres, lifted by enormous convection currents.

Eruption columns may be transient, if formed by a discrete explosion, or sustained, if produced by a continuous eruption or closely spaced discrete explosions.


The solid and/or liquid materials in an eruption column are lifted by processes which vary as the material ascends: [1]

Column heights

Eruption column rising over Redoubt Volcano, Alaska MtRedoubtedit1.jpg
Eruption column rising over Redoubt Volcano, Alaska

The column will stop rising once it attains an altitude where it is more dense than the surrounding air. Several factors control the height that an eruption column can reach.

Intrinsic factors include the diameter of the erupting vent, the gas content of the magma, and the velocity at which it is ejected. Extrinsic factors can be important, with winds sometimes limiting the height of the column, and the local thermal temperature gradient also playing a role. The atmospheric temperature in the troposphere normally decreases by about 6-7 K/km, but small changes in this gradient can have a large effect on the final column height. Theoretically, the maximum achievable column height is thought to be about 55 km (34 mi). In practice, column heights ranging from about 2–45 km (1.2–28.0 mi) are seen.

Eruption columns with heights of over 20–40 km (12–25 mi) break through the tropopause and inject particulates into the stratosphere. Ashes and aerosols in the troposphere are quickly removed by precipitation, but material injected into the stratosphere is much more slowly dispersed, in the absence of weather systems. Substantial amounts of stratospheric injection can have global effects: after Mount Pinatubo erupted in 1991, global temperatures dropped by about 0.5 °C (0.90 °F). The largest eruptions are thought to cause temperature drops down to several degrees, and are potentially the cause of some of the known mass extinctions.

Eruption column heights are a useful way of measuring eruption intensity since for a given atmospheric temperature, the column height is proportional to the fourth root of the mass eruption rate. Consequently, given similar conditions, to double the column height requires an eruption ejecting 16 times as much material per second. The column height of eruptions which have not been observed can be estimated by mapping the maximum distance that pyroclasts of different sizes are carried from the vent—the higher the column the further ejected material of a particular mass (and therefore size) can be carried.

The approximate maximum height of an eruption column is given by the equation.

H = k(MΔT)1/4


k is a constant that depends on various properties, such as atmospheric conditions.
M is the mass eruption rate.
ΔT is the difference in temperature between the erupting magma and the surrounding atmosphere.


Column collapse

Eruption columns may become so laden with dense material that they are too heavy to be supported by convection currents. This can suddenly happen if, for example, the rate at which magma is erupted increases to a point where insufficient air is entrained to support it, or if the magma density suddenly increases as denser magma from lower regions in a stratified magma chamber is tapped.

If it does happen, then material reaching the bottom of the convective thrust region can no longer be adequately supported by convection and will fall under gravity, forming a pyroclastic flow or surge which can travel down the slopes of a volcano at speeds of over 100–200 km/h (62–124 mph). Column collapse is one of the most common and dangerous volcanic hazards in column-creating eruptions.


Several eruptions have seriously endangered aircraft which have encountered or passed by the eruption column. In two separate incidents in 1982, airliners flew into the upper reaches of an eruption column blasted off by Mount Galunggung, and the ash severely damaged both aircraft. Particular hazards were the ingestion of ash stopping the engines, the sandblasting of the cockpit windows rendering them largely opaque and the contamination of fuel through the ingestion of ash through pressurisation ducts. The damage to engines is a particular problem since temperatures inside a gas turbine are sufficiently high that volcanic ash is melted in the combustion chamber, and forms a glass coating on components further downstream of it, for example on turbine blades.

In the case of British Airways Flight 9, the aircraft lost power on all four engines, and in the other, nineteen days later, three of the four engines failed on a Singapore Airlines 747. In both cases, engines were successfully restarted but the aircraft were forced to make emergency landings in Jakarta.

Similar damage to aircraft occurred due to an eruption column over Redoubt volcano in Alaska in 1989. Following the eruption of Mount Pinatubo in 1991, aircraft were diverted to avoid the eruption column, but nonetheless, fine ash dispersing over a wide area in Southeast Asia caused damage to 16 aircraft, some as far as 1,000 km (620 mi) from the volcano.

Eruption columns are not usually visible on weather radar and may be obscured by ordinary clouds or night. [2] Because of the risks posed to aviation by eruption columns, there is a network of nine Volcanic Ash Advisory Centers around the world which continuously monitor for eruption columns using data from satellites, ground reports, pilot reports and meteorological models. [3]

See also

Related Research Articles

Volcano rupture in the crust of a planetary-mass object that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface

A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.

Volcanic Explosivity Index qualitative scale indicating the explosive intensity of volcanic eruptions

The Volcanic Explosivity Index (VEI) is a relative measure of the explosiveness of volcanic eruptions. It was devised by Chris Newhall of the United States Geological Survey and Stephen Self at the University of Hawaii in 1982.

Mount Vesuvius Stratovolcano in the Gulf of Naples, Italy

Mount Vesuvius is a somma-stratovolcano located on the Gulf of Naples in Campania, Italy, about 9 km (5.6 mi) east of Naples and a short distance from the shore. It is one of several volcanoes which form the Campanian volcanic arc. Vesuvius consists of a large cone partially encircled by the steep rim of a summit caldera caused by the collapse of an earlier and originally much higher structure.

Stratovolcano Tall, conical volcano built up by many layers of hardened lava and other ejecta

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, 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).

Pyroclastic rock Clastic rocks composed solely or primarily of volcanic materials

Pyroclastic rocks or pyroclastics are sedimentary clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, these rocks are termed volcaniclastic. Commonly associated with unsieved volcanic activity—such as Plinian or krakatoan eruption styles, or phreatomagmatic eruptions—pyroclastic deposits are commonly formed from airborne ash, lapilli and bombs or blocks ejected from the volcano itself, mixed in with shattered country rock.

Mount Pinatubo active stratovolcano on the island of Luzon in the Philippines

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 activities of 1991, just before June. Pinatubo was heavily eroded, inconspicuous and obscured from view. It was covered with dense forests which supported a population of several thousand indigenous Aetas.

Cerro Negro mountain

Cerro Negro is an active volcano in the Cordillera de los Maribios mountain range in Nicaragua, about 10 km (6.2 mi) from the village of Malpaisillo. It is a very new volcano, the youngest in Central America, having first appeared in April 1850. It consists of a gravelly basaltic cinder cone, which contrasts greatly with the surrounding verdant hillsides, and gives rise to its name, which means Black Hill. Cerro Negro has erupted frequently since its first eruption. One unusual aspect of several eruptions has been the emission of ash from the top of the cone, while lava erupts from fractures at the base.

Plinian eruption type of volcanic eruption

Plinian eruptions or Vesuvian eruptions are volcanic eruptions marked by their similarity to the eruption of Mount Vesuvius in 79 AD, which destroyed the ancient Roman cities of Herculaneum and Pompeii. The eruption was described in a letter written by Pliny the Younger, after the death of his uncle Pliny the Elder.

Cerro Azul (Chile volcano) mountain in Curicó Province Chile

Cerro Azul, sometimes referred to as Quizapu, is an active stratovolcano in the Maule Region of central Chile, immediately south of Descabezado Grande. Part of the South Volcanic Zone of the Andes, its summit is 3,788 meters (12,428 ft) above sea level, and is capped by a summit crater that is 500 meters (1,600 ft) wide and opens to the north. Beneath the summit, the volcano features numerous scoria cones and flank vents.

Mount Hudson mountain in Aysén Province Chile

Mount Hudson is a stratovolcano in southern Chile, and the site of one of the largest eruptions in the twentieth century. The mountain itself is covered by a glacier. There is a caldera at the summit from an ancient eruption; modern volcanic activity comes from inside the caldera. Mount Hudson is named after Francisco Hudson, a 19th-century Chilean Navy hydrographer.

Strombolian eruption type of volcanic eruption

A Strombolian eruption is a type of volcanic eruption with relatively mild blasts, having a volcanic explosivity index of about 1 to 3. Strombolian eruptions consist of ejection of incandescent cinders, lapilli, and lava bombs, to altitudes of tens to a few hundreds of metres. The eruptions are small to medium in volume, with sporadic violence. This type of eruption is named for the Italian volcano Stromboli.

Explosive eruption Type of volcanic eruption in which lava is violently expelled

In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such that expelled lava violently froths into volcanic ash when pressure is suddenly lowered at the vent. Sometimes a lava plug will block the conduit to the summit, and when this occurs, eruptions are more violent. Explosive eruptions can send rocks, dust, gas and pyroclastic material up to 20 km (12 mi) into the atmosphere at a rate of up to 100,000 tonnes per second, traveling at several hundred meters per second. This cloud may then collapse, creating a fast-moving pyroclastic flow of hot volcanic matter.

A pyroclastic fall is a uniform deposit of material which has been ejected from a volcanic eruption or plume such as an ash fall or tuff. Pyroclastic air fall deposits are a result of:

  1. Ballistic transport of ejecta such as volcanic blocks, volcanic bombs and lapilli from volcanic explosions
  2. Deposition of material from convective clouds associated with pyroclastic flows such as coignimbrite falls
  3. Ejecta carried in gas streaming from a vent. The material under the action of gravity will settle out from an eruption plume or eruption column
  4. Ejecta settling from an eruptive plume or eruption column that is displaced laterally by wind currents and is dispersed over great distances
Types of volcanic eruptions Basic mechanisms of eruption and variations

Several types of volcanic eruptions—during which lava, tephra, and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series.

Operation Fiery Vigil

Operation Fiery Vigil was the emergency evacuation of all non-essential military and U.S. Department of Defense civilian personnel and their dependents from Clark Air Base and U.S. Naval Base Subic Bay during the June 1991 eruption of Mount Pinatubo in the Philippines.

Dense-rock equivalent is a volcanologic calculation used to estimate volcanic eruption volume. One of the widely accepted measures of the size of a historic or prehistoric eruption is the volume of magma ejected as pumice and volcanic ash, known as tephra during an explosive phase of the eruption, or the volume of lava extruded during an effusive phase of a volcanic eruption. Eruption volumes are commonly expressed in cubic kilometers (km3).

Cinder cone A steep conical hill of loose pyroclastic fragments around a volcanic vent

A cinder cone is a steep conical hill of loose pyroclastic fragments, such as either volcanic clinkers, volcanic ash, or cinder that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions or lava fountains from a single, typically cylindrical, vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as either cinders, clinkers, or scoria around the vent to form a cone that often is symmetrical; with slopes between 30–40°; and a nearly circular ground plan. Most cinder cones have a bowl-shaped crater at the summit.

2010 eruptions of Eyjafjallajökull volcanic events in Iceland

The 2010 eruptions of Eyjafjallajökull were volcanic events at Eyjafjallajökull 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 continued into May 2010. The eruption was declared officially over in October 2010, when snow on the glacier did not melt. From 14–20 April, ash from the volcanic eruption covered large areas of Northern Europe. About 20 countries closed their airspace to commercial jet traffic and it affected approximately 10 million travellers.

Tectonic–climatic interaction is the interrelationship between tectonic processes and the climate system. The tectonic processes in question include orogenesis, volcanism, and erosion, while relevant climatic processes include atmospheric circulation, orographic lift, monsoon circulation and the rain shadow effect. As the geological record of past climate changes over millions of years is sparse and poorly resolved, many questions remain unresolved regarding the nature of tectonic-climate interaction, although it is an area of active research by geologists and palaeoclimatologists.

Volcanic ash volcanic material formed during explosive eruptions with the diameter of the grains less than 2 mm

Volcanic ash consists of fragments of rock, minerals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer to all explosive eruption products, including particles larger than 2 mm. Volcanic ash is formed during explosive volcanic eruptions when dissolved gases in magma expand and escape violently into the atmosphere. The force of the gasses shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during phreatomagmatic eruptions, causing the water to explosively flash to steam leading to shattering of magma. Once in the air, ash is transported by wind up to thousands of kilometres away.


  1. "How volcanoes work - The eruption model (QuickTime movie)". San Diego State University. Archived from the original on 2007-07-01. Retrieved 2007-06-30.
  2. Mitchell Roth; Rick Guritz (July 1995). "Visualization of Volcanic ash clouds". IEEE Computer Graphics and Applications. 15 (4): 34–39. doi:10.1109/38.391488.
  3. "Keeping aircraft clear of volcanic ash - Darwin Volcanic Ash Advisory Center". Australian Government - Bureau of Meteorology. Retrieved 2007-06-30.

Further reading