sampling lava using a rock hammer and a bucket of water
Eruption of Stromboli
(Isole Eolie/Italia), ca. 100m (300ft) vertically. Exposure of several seconds. The dashed trajectories are the result of lava pieces with a bright hot side and a cool dark side rotating in mid-air.
is a geologist
who studies the eruptive activity and formation of volcanoes and their current and historic eruptions. Volcanologists frequently visit volcanoes, especially active ones, to observe volcanic eruptions
, collect eruptive products including tephra
(such as ash
samples. One major focus of enquiry is the prediction of eruptions; there is currently no accurate way to do this, but predicting eruptions, like predicting earthquakes, could save many lives.
Volcanologist examining tephra
horizons in south-central Iceland
A diagram of a destructive plate margin
, where subduction fuels volcanic activity at the subduction zones of tectonic plate boundaries.
Seismic observations are made using seismographs
deployed near volcanic areas, watching out for increased seismicity during volcanic events, in particular looking for long period harmonic tremors, which signal magma
movement through volcanic conduits.
Surface deformation monitoring
includes the use of geodetic techniques such as leveling, tilt, strain, angle and distance measurements through tiltmeters, total stations and EDMs. This also includes GNSS observations
Surface deformation indicates magma upwelling: increased magma supply
produces bulges in the volcanic center's surface.
Gas emissions may be monitored with equipment including portable ultra-violet spectrometers (COSPEC, now superseded by the miniDOAS), which analyzes the presence of volcanic gases
such as sulfur dioxide
; or by infra-red spectroscopy (FTIR). Increased gas emissions, and more particularly changes in gas compositions, may signal an impending volcanic eruption.
Temperature changes are monitored using thermometers and observing changes in thermal properties of volcanic lakes and vents, which may indicate upcoming activity.
are widely used to monitor volcanoes, as they allow a large area to be monitored easily. They can measure the spread of an ash plume, such as the one from Eyjafjallajökull
's 2010 eruption,
as well as SO2
and thermal imaging can monitor large, scarcely populated areas where it would be too expensive to maintain instruments on the ground.
Other geophysical techniques
(electrical, gravity and magnetic observations) include monitoring fluctuations and sudden change in resistivity, gravity anomalies or magnetic anomaly patterns that may indicate volcano-induced faulting and magma upwelling.
includes analyzing tephra
and lava deposits and dating these to give volcano eruption patterns,
with estimated cycles of intense activity and size of eruptions.
Volcanology has an extensive history. The earliest known recording of a volcanic eruption may be on a wall painting dated to about 7,000 BCE found at the Neolithic
site at Çatal Höyük in Anatolia
. This painting has been interpreted as a depiction of an erupting volcano, with a cluster of houses below shows a twin peaked volcano in eruption, with a town at its base (though archaeologists now question this interpretation).
The volcano may be either Hasan Dağ
, or its smaller neighbour, Melendiz Dağ.
Eruption of Vesuvius
in 1822. The eruption of CE 79 would have appeared very similar.
The classical world of Greece and the early Roman Empire
explained volcanoes as sites of various gods. Greeks considered that Hephaestus
, the god of fire, sat below the volcano Etna
, forging the weapons of Zeus
. The Greek word used to describe volcanoes was etna
, or hiera
, after Heracles
, the son of Zeus. The Roman poet Virgil
, in interpreting the Greek mythos, held that the giant Enceladus
was buried beneath Etna by the goddess Athena as punishment for rebellion against the gods; the mountain's rumblings were his tormented cries, the flames his breath and the tremors his railing against the bars of his prison. Enceladus' brother Mimas
was buried beneath Vesuvius
by Hephaestus, and the blood of other defeated giants welled up in the Phlegrean Fields surrounding Vesuvius.
The Greek philosopher Empedocles
(c. 490-430 BCE) saw the world divided into four elemental forces, of Earth, Air, Fire and Water. Volcanoes, Empedocles maintained, were the manifestation of Elemental Fire. Plato contended that channels of hot and cold waters flow in inexhaustible quantities through subterranean rivers. In the depths of the earth snakes a vast river of fire, the Pyriphlegethon
, which feeds all the world's volcanoes. Aristotle considered underground fire as the result of "the...friction of the wind when it plunges into narrow passages."
Wind played a key role in volcano explanations until the 16th century. Lucretius
, a Roman philosopher, claimed Etna was completely hollow and the fires of the underground driven by a fierce wind circulating near sea level. Ovid believed that the flame was fed from "fatty foods" and eruptions stopped when the food ran out. Vitruvius
contended that sulfur, alum and bitumen fed the deep fires. Observations by Pliny the Elder
noted the presence of earthquakes preceded an eruption; he died in the eruption of Vesuvius
in 79 CE while investigating it at Stabiae
. His nephew, Pliny the Younger
, gave detailed descriptions of the eruption in which his uncle died, attributing his death to the effects of toxic gases. Such eruptions have been named Plinian
in honour of the two authors.
After the first eruption of Mount St. Helens
on May 18, five more explosive eruptions occurred in 1980, including this event on July 22. This eruption sent pumice and ash 6 to 11 miles (10-18 kilometers) into the air, and was visible in Seattle
, Washington, 100 miles (160 kilometers) to the north. The view here is from the south.
were described from the Azores in 1580. Georgius Agricola
argued the rays of the sun, as later proposed by Descartes
had nothing to do with volcanoes. Agricola believed vapor under pressure caused eruptions of 'mointain oil' and basalt.
Jesuit Athanasius Kircher
(1602–1680) witnessed eruptions of Mount Etna and Stromboli, then visited the crater of Vesuvius and published his view of an Earth with a central fire connected to numerous others caused by the burning of sulfur, bitumen and coal.
considered volcanoes as conduits for the tears and excrement of the Earth, voiding bitumen, tar and sulfur. Descartes, pronouncing that God had created the Earth in an instant, declared he had done so in three layers; the fiery depths, a layer of water, and the air. Volcanoes, he said, were formed where the rays of the sun pierced the earth.
Science wrestled with the ideas of the combustion of pyrite
with water, that rock was solidified bitumen, and with notions of rock being formed from water (Neptunism
). Of the volcanoes then known, all were near the water, hence the action of the sea upon the land was used to explain volcanism
Interaction with religion and mythology
Pele's hair caught on a radio antenna mounted on the south rim of Puʻu ʻŌʻō
, July 22, 2005
Tribal legends of volcanoes
abound from the Pacific Ring of Fire
and the Americas, usually invoking the forces of the supernatural or the divine to explain the violent outbursts of volcanoes. Taranaki
, according to Māori mythology, were lovers who fell in love with Pihanga
, and a spiteful jealous fight ensued. Māori will not to this day live between Tongariro and Taranaki for fear of the dispute flaring up again.
is patron saint of Catania
, close to mount Etna, and an important highly venerated (till today
) example of virgin martyrs of Christian antiquity.
In 253 CE, one year after her violent death, the stilling of an eruption of Mt. Etna was attributed to her intercession. Catania was however nearly completely destroyed by the eruption of Mt. Etna in 1169, and over 15,000 of its inhabitants died. Nevertheless, she was invoked again for the 1669 Etna eruption
and, for an outbreak danginering Nicolosi
The way she is invoked and dealt with in Italian Folk religion
, a sort of quid pro quo way approach to saints, has been related (in the tradition of James Frazer
) to earlier pagan believes.
In 1660 the eruption of Vesuvius rained twinnedpyroxene
crystals and ash upon the nearby villages. The crystals resembled the crucifix and this was interpreted as the work of Saint Januarius
. In Naples
, the relics of St Januarius are paraded through town at every major eruption of Vesuvius. The register of these processions and the 1779 and 1794 diary of Father Antonio Piaggio allowed British diplomat and amateur naturalist Sir William Hamilton
to provide a detailed chronology and description of Vesuvius' eruptions.
Spanish depiction of a volcanic eruption in Guatemala, 1775.
- Plato (428–348 BC)
- Pliny the Elder (23–79 AD)
- Pliny the Younger (61 – c. 113 AD)
- George-Louis Leclerc, Comte de Buffon (1707–1788)
- James Hutton (1726–1797)
- Déodat Gratet de Dolomieu (1750–1801)
- George Julius Poulett Scrope (1797–1876)
- Giuseppe Mercalli (1850–1914)
- Thomas Jaggar (1871–1953), founder of the Hawaiian Volcano Observatory
- Haroun Tazieff (1914–1998), advisor to the French Government and Jacques Cousteau
- George P. L. Walker (1926–2005), pioneering volcanologist who transformed the subject into a quantitative science
- Haraldur Sigurdsson (born 1939), Icelandic volcanologist and geochemist
- Katia and Maurice Krafft (1942–1991 and 1946–1991, respectively), died at Mount Unzen in Japan, 1991
- David A. Johnston (1949–1980), killed during the 1980 eruption of Mount St. Helens
- Harry Glicken (1958–1991), died at Mount Unzen in Japan, 1991
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