Volcanology

Volcanology (also spelled vulcanology) is the study of volcanoes, lava, magma, and related geological, geophysical and geochemical phenomena. The term volcanology is derived from the Latin word vulcan. Vulcan was the ancient Roman god of fire.

A volcanologist is a person who studies the 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 or pumice), rock and lava 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.

History of volcanology
The earliest known recording of a volcanic eruption may be on a wall painting dated to about 7000 BCE found at the Neolithic site at Çatal Höyük (now known as Çatalhöyük), in Anatolia, Turkey. 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.

Mythical explanationsThe classical world of Greece and the early Roman Empire explained volcanoes as the work of the gods as science and alchemy had no explanation for their existence. Grecian myths and tales tell of Atlantis, a fabled island that sank into the sea. Plato (428-348 BCE) told of the disappearance of a vast island and its powerful civilization, the Atlanteans, in two of his dialogues, Critias and Timaeus.

It is now considered that the island of Thera, now Santorini, in the Aegean Sea, was destroyed by a tremendous series of volcanic explosions around 1620 BCE, with ash falls of up to a foot deep recorded in Turkey. The explosion of Thera sent colossal tsunamis, estimated at 100 feet height, racing across the Aegean, and the southern coast of Crete. Other recordings of the Thera eruption spawned Greek myths, namely the Deucalion, in which Poseidon, god of the sea, took revenge upon Zeus by inundating Attica, Argolis, Salonika, Rhodes and the coast of Lycia (Turkey) to Sicily.

Greeks also considered that Hephaestus, the god of fire, sat below the volcano Etna, forging the weapons of Zeus. His minions, the cyclops with their single staring eye, may be an allegory to the round craters and cones of a volcano. Indeed, 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 hero Enceladus was buried beneath Etna by the goddess Athena as punishment for disobeying 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.

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 and Tongariro, 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.

Greco-Roman science The first attempt at a scientific explanation of volcanoes was undertaken by the Greek philosopher Empedocles (c. 490-430 BCE), who 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.

Christian mythology
The study of volcanology was not advanced much between the days of Plato and Hutton. The Christian world explained volcanoes by a multitude of prescientific notions, but it was also thought they were the work of Satan or the wrath of God, and only saintly miracles could avert their wrath. For this reason the relics of Saint Agatha were paraded in front of lava advancing on Catania in 253 CE, and miraculously the lava clove in two (down two valleys) and spared the town. Unfortunately the relics of St. Agatha proved ineffective in 1669, with the loss of much of Catania to Etna's lava.

In 1660 the eruption of Vesuvius rained twinned pyroxene crystals and ash upon the nearby villages. The twinned pyroxene 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 eructation of Vesuvius. The register of these processions allowed British diplomat and amateur naturalist Sir William Hamilton to document Vesuvius' eruptions, one of the first few 'scientific' studies of the eruptive history of a volcano.

Renaissance observations
Renaissance descriptions of volcanoes vastly improved the state of knowledge, despite the resistance of the Church to scientific explorations of the natural world, especially those at odds with Biblical teachings. Nevertheless, nuées ardentes 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.

Johannes Kepler 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.

Modern volcanology
Volcanologist examining tephra horizons in south-central Iceland.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.[3]

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 and InSAR.[4] 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.[3]

Temperature changes are monitored using thermometers and observing changes in thermal properties of volcanic lakes and vents, which may indicate upcoming activity.

Satellites 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 Eyjafjallajokull's 2010 eruption, as well as SO2 emissions. InSAR 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.

Stratigraphic analyses includes analyzing tephra and lava deposits and dating these to give volcano eruption patterns, with estimated cycles of intense activity and size of eruptions.