Bill Casselman

Increase your English vocabulary by learning technical terms naming volcanoes & volcanic entities

At the Wording Desk

A volcano: the upchuck of inner earth. In November of 2012, the Plosky Tolbachik volcano on the remote Kamchatka peninsula of western Russia erupted anew and brought into world news both familiar and obscure English technical terms in volcanology. These English volcanic labels adopted from other languages are a delightful word upheaval to prod and explore.

First, to help you remember the peak’s name, here’s a bit of Russian vocabulary. Ploskii плоский means ‘flat, flat-topped.’ It has a brother volcano in the same mountain area called Ostry Tolbachik. Ostrii острый means ‘sharp, pointed, peaked’ in Russian. Tolbachik appears to be the surname of a pioneer who first prospected a nearby valley of the same name.



Let’s begin with a very familiar volcano word of which few people know the origin. The word lava comes into the languages of Europe and into English directly from one famous volcano, Mount Vesuvius near Naples, which blew its top and famously buried the Roman towns of Pompeii and Herculaneum in 79 CE. Lava began in Italian meaning ‘a “wash” as in a ditch, a rain ditch through soil dug by a heavy downpour.’ Neapolitans used the word to refer to a Vesuvian lava stream, for they rightly feared the undulant unguent of molten magma, the lithic pre-lava lurking beneath the rocky crust of Vesuvio, awaiting an urge to erupt. Melted lava was like a ‘wash of rock’ sliding in a slow obliterative slip of death down the peril-rich flanks of Vesuvius.

Lava’s root is the Latin verb lavare ‘to wash,’ cognate with Greek λούειν louein ‘to wash the body’ and possibly with West German forms like Old English lafian ‘to pour water on the body’ and modern German laben ‘to refresh.’

This old Indo-European stem gives English words like lather which in its Old English form léaðor referred to washing soda, and then came to mean frothy foam of soap and water, cognate with Greek λοετρόν, λουτρόν ‘bath.’

Magma is one of my pet words in volcanology. Magma is molten rock semi-liquid in nature. After magma is expelled from a volcano it is called lava. The root is a Greek verb massein ‘to mix, to mingle together.’

Pahoehoe (puh-HOY-hoy) is a type of Hawaiian lava that upwells from the fissured rift of its volcano; it is smooth, gelatinous, billowy, unbroken and fluid; then this lava cools into ropy cords. Or as pahoehoe loses heat and de-gasses, a second kind of flow, a’a lava, may be formed. A’a or aa, beloved of crossword puzzle fans, is a rough-surfaced and viscid lava. Some outflows of pahoehoe have been compared to glistening folds of poured taffy.

Hawaiian Etymology of Pahoehoe
Hoe is a Hawaiian noun meaning ‘oar’ or ‘canoe paddle.’ Pā.hoe is a verb meaning ‘to paddle an outrigger canoe.’ The single-hulled outrigger was ideal for near-shore Polynesian fishing. Pahoehoe is a reduplicated verb form of pahoe meaning ‘to paddle a canoe very quickly.’ It is a Hawaiian fishing technique, during which canoeists beat their paddles in unison against the gunwales of their canoes or the sides, in order to make a racketing, thumping noise that frightens and then drives fish into a nearby net.

Hawaiians borrowed this word to describe a type of lava because the flow and shiny crust of pahoehoe lava resembled the surface of seawater beaten rhythmically by many canoeists’ paddles. (?)

 A’a’ - a kind of lava
As every deft Scrabble player knows, aa or a’a’ (pronounced ah-ah) is one of the two kinds of lava that pours forth from Hawaiian volcanoes. As lavas go, aa is rough and looks like slag with bubble holes. As molten aa cools after being exposed to air, gases formed by the melting magma escape, hissing and emitting blister bubbles that burst on the cooling lava surface to give aa its characteristic scoriaceous aspect. The root meaning of a'a' in Polynesian is the eminently practical one of 'burn-burn.'

Tephra τέϕρα is the classical Greek word for ash or ashes. In modern volcanology, tephra is rock bits and dust propelled into the upper air by the force of an eruption. Tephra settles in banded layers in the vicinity of volcanoes.

It is a noun often used attributively, that is, like an adjective in appositive clusters, such as tephra layer, tephra cloud, tephra rain. In attribution, nouns are used like adjectives. They add a distinguishing or characteristic quality to the noun they modify as attributive adjectives.

Tephrite is a basaltic rock found in volcanic debris.

Sometimes, previous volcanic eruptions can be dated by studying layers of tephra and this is called tephrochronology.

In olden days, wizards and diviners claimed to tell a gullible person’s future by throwing ashes up into the air and observing how such ashes were carried by the wind. This scamming of hapless dupes was sometimes given the fancy name of tephromancy.


Breccia names a composite sandy or clayey rock crammed with smaller sharp rock fragments. It is one of the Italian words not from Latin, but borrowed early from some Germanic source, because breccia is cognate with our English verb to break, with older German brechan ‘to break.’ French and Spanish borrowed from the same Germanic source to get their words: French brèche ‘breaking, breach’ and Spanish brecha.

A diatreme is literally a through-hole, a modern compound word made up of Greek dia διά ‘through’ + Greek trema τρῆμα ‘hole, orifice, opening.’ A diatreme is a small vent or pipe-like opening forced wide by volcanic gases during an eruption and then filled with breccia debris (as defined above).

A guyot is a flat-topped, undersea mountain formed from a volcano. This word guyot is a notorious example of why eponyms are a bad idea in scientific nomenclature. Supposedly the name was given to honor the discoverer of these oceanographic tablemounts, a Swiss geographer named Arnold H. Guyot. How nice. And now that is their legitmate name in science. But — Oh Dear! — Monsieur Guyot did NOT discover them. Their discoverer was Professor H. Hess of Princeton University. Now, Hessless they hiss incessantly, submerged and ashamed. No, they don’t hiss but they ought to.

Therefore the two common synonyms for guyot are much better, more descriptive and more honest names: seamount and, even better as a lay name, tablemount, because it describes neatly these relatively common features of the Pacific Ocean floor. The flat nature of their level summits are probably due to incessant wave action.

A fumarole is a vent from which volcanic gases escape in vaporous urgency. Fumaroles can occur along small cracks or long fissures. When a fumarole belches forth chiefly sulphurous effluvium, an Italian word is used in English geology to describe such a vent: solfatara.

Fumarole was borrowed into English from Italian fumarola ‘chimney’ from a post-classical Latin diminutive form fumariolum ‘little smoke hole, slit, chimney pot, vent’ from a simpler, earlier diminutive Latin noun fumarium, originally a small smokehouse used to age wine, itself from Latin fumus ‘smoke,’ source of our common English word, fume.


Note the deposition of sulphur from a fumarole or solfatara on Mount Washington, as scientists from the United States Geological Survey take measurements.

A kipuka (KEE-pooka) is a habitat that supports scant and fragile life forms while surrounded by an earlier lava wasteland. The German word sums it up succinctly: eine Vegetationsinsel ‘a little island of vegetation’ surrounded by lava flows. Kipuka is a Hawaiian word for ‘opening.’ Puka in Hawaiian refers to a ‘gap, perforation, blank space in a form.’ Ki- is a prefix that intensifies or augments the root word. Kipuka’s non-volcanic meanings include ‘a clearing in a forest’ or ‘an open space in clouds.’

Lapilli are teeny bits of shattered rock or exploded lava debris smaller than 64 millimeters wide which are propelled from volcanos. The word is a pure Latin plural meaning ‘little stones’ derived from lapillus, one of the Latin words for pebble, itself from lapis ‘stone.’ Lapilli may also stand as a plural of the Italian form of the word, lapillo. When the stones of a wall or building have fallen down, the structure may be said to be delapidated!

A maar is a shallow volcanic crater that sometimes fills with water and forms a flat-bottomed lake. There are two plural forms: Maare and maars. The word is a German locative, occurring in German place names to delineate a place with a crater-lake. German Maar looks like a version of mara, a Latin word for pond or swamp.

This exotic French term, pronounced aloud, trembles on the English lip. In volcanology nuée ardente ‘burning cloud’ names a luminous cloud of glowing gases, lava debris, pumice and air-borne ash, an incandescing volcanic down-spew, a particulate-dense, roiling cloud of pyroclastic flow [see below] from an erupting volcano. One science writer called it “the glow of the flow.” To be engulfed in such a poison shroud is doom.

The French plural is used in English scientific writing: nuées ardentes.


A speeding truck tries to outrun the billowing surge, the toxic quilt of a nuée ardente.

Etymology of Nuée
The common French word for cloud is nuage, with both positive and pejorative meanings. Its etymon is Latin nubes, with its Latin diminutive form, borrowed directly into English, nebula, prime meaning ‘vapour, mist.’ In early eleventh-century French there was another form of this word for cloud taken from nuba, a colloquial variant in street Latin of the time, la nue ‘cloud.’ Eventually, to the simple word nue was added a collective suffix -age to give nuage, prime meaning: a group of clouds, an overcast sky, etc. Then, after existing in written French with a collective sense, nuage dwindled in meaning to once again refer to a single cloud.

Nue also had an augmentative form, la nuée which signified a big cloud, a cloud full of rain, dark and threatening. That was indeed the reasonable French cloud word to borrow when naming the volcanic nightmare cloud.

Today, in modern French, la nuée is almost exclusively negative: la nuée d’orage ‘the thundercloud or storm cloud’; une nuée de paparazzi ‘a horde of annoying photographers’; une nuée de sauterelles ‘a plague of locusts.’


One of the most interesting extensions of nuage and Latin nubes is something originally thought to be caused by clouds, namely, shade, or in French la nuance. The developed meanings began in French with nuance denoting the hue of a colour, any differentiating qualitative subtleties, the finer points of an argument, the shades of a personality etc. These developed meanings gained the most use in English.

Some Indo-European cognates of Latin nubes are: modern German Nebel ‘mist,’ classical Greek νέϕος nephos ‘cloud,’ Sanskrit nabhas ‘cloud,’ Old Norse njol ‘shadows,’ Welsh niwl ‘fog, mist’ and Old Church Slavonic nebo ‘heaven.’ Nephology is the scientific study of clouds.

Even our word nubile ‘beautiful, worthy of marriage or able to marry’ shared the same root; nubile is the adjective of capability from the Latin verb nubere which meant in its prime sense ‘to veil the head,’ that is, in a sense, to becloud the head with a veil, thence to wear the veil of marriage, and thence nubere meant ‘to get married.’

A nasalized form of the root appears in the Latin word nimbus, which meant at first a cloud filled with rain, thunder and lightning, thence a golden cloud circling the head of an Olympian god; later a nimbus was a golden aura glowing about the head of any divine being, such as Christ or Buddha. In meteorology, the word names a type of plump cloud: cumulonimbus.

Outgassing is the release of gases into the atmosphere during volcanic eruptions. During the ancient, violent formation of the world’s mantle, some of earth’s atmosphere (including some water vapor, nitrogen and argon) originated from outgassing.

Phreatic Eruption

It is a violent eruption of steam when water frazzles and boils to instant steam on hot volcanic rocks. Phreatic first referred to underground water located below the water table. A developed meaning in geology sees phreatic denominate an eruption that involves hot liquid rock, magma, meeting underground water to produce explosive steam and mud that explodes and blasts its way up to the surface through the lava vents. The term was coined as a modern adjectival form of the ancient Greek word for a cistern, reservoir or well, ϕρέαρ phear and its word-forming genitive ϕρέατος phreatos.

The map below shows the location of Mount Vesuvius on the Bay of Naples.


This is one of the most explosive types of volcanic eruptions, known for producing nuées ardentes and columns of gas and debris that may soar miles-high into the stratosphere. It’s named after the Roman writer Pliny the Younger who observed and wrote a description of the famous eruption of Mount Vesuvius in 79 CE, the volcano that buried Pompeii and Herculaneum near Naples. Pliny’s uncle, also a writer, of one of the great encyclopaedias in Latin, died in the eruption. Here is part of his nephew’s description.

“On the 24th of August, about one in the afternoon, my mother desired him to observe a cloud which appeared of a very unusual size and shape. He had just taken a turn in the sun and, after bathing himself in cold water, and making a light luncheon, gone back to his books: he immediately arose and went out upon a rising ground from whence he might get a better sight of this very uncommon appearance. A cloud, from which mountain was uncertain, at this distance (but it was found afterwards to come from Mount Vesuvius), was ascending, the appearance of which I cannot give you a more exact description of than by likening it to that of a pine tree, for it shot up to a great height in the form of a very tall trunk, which spread itself out at the top into a sort of branches; occasioned, I imagine, either by a sudden gust of air that impelled it, the force of which decreased as it advanced upwards, or the cloud itself being pressed back again by its own weight, expanded in the manner I have mentioned; it appeared sometimes bright and sometimes dark and spotted, according as it was either more or less impregnated with earth and cinders. This phenomenon seemed to a man of such learning and research as my uncle extraordinary and worth further looking into.”

- - - Sixth Book, Letter 16, of Pliny the Younger's Epistulae 'Letters to his Friends', translation by William Melmoth, a translation now in the public domain


               Vesuvius blows a Plinian volcano in 1882

Wikipedia then continues with a summary of what happened next: “Pliny the Elder set out to rescue the victims from their perilous position on the shore of the Bay of Naples, and launched his galleys, crossing the bay to Stabiae (near the modern town of Castellammare di Stabia). Pliny the Younger provided an account of his death, and suggested that he collapsed and died through inhaling poisonous gases emitted from the volcano. His body was found interred under the ashes of the Vesuvius with no apparent injuries on 26 August, after the plume had dispersed, confirming asphyxiation or poisoning.”

Pyroclastic literally means ‘broken apart and reduced in size by fire.’ The roots are the Greek word for fire πῦρ pyr + -κλάστης ‘thing that breaks up, smasher’ from the Greek verb klan ‘to break.’ An iconoclast was originally a thug who broke holy icons.

One of the deadliest concomitants of a Vesuvian eruption is the pyroclastic flow during which an unstoppable torrent of burning hot toxic gases, lava and sundry melting igneous debris cascade down the flanks of an erupting volcano melting and killing everything in its path.

A tuya is a flat-topped, steep-sided volcano, as in the picture below of a tuya in Iceland, formed when lava bursts through thick ice or erupts under a glacier. Wikipedia states that “they are somewhat rare worldwide, being confined to regions which were covered by glaciers and had active volcanism during the same period.” The word appears to come from Tuya Butte in the Tuya mountain range of northern British Columbia in Canada and was coined by Canadian geologist Bill Mathews.

Etymology of the Word Volcano
Volcanus or Vulcanus was the Roman god of fire, the blacksmith of the immortals, his smithy wreathed in clouds of smoke as he honed Jupiter’s swords and fashioned winged shoes for flying horses. I think there are possible cognates of Vulcanus in the English noun welkin ‘a cloud, realm of the clouds, the heavens’ and modern German die Wolke ‘the cloud.’ The Oxford English Dictionary offers a much less probable Arabic source of the Italian island name. Mount Etna’s earliest name in Latin was Vulcanus mons ‘Mount Vulcan.’ The Aeolian Islands north of Sicily still have active volcanoes on islands now called Stromboli and Vulcano. The OED thinks burkan, one of the common words for ‘volcano’ in Arabic, gave the islands their early name. I think the borrowing took place the other way. Arabic borrowed volcan and heard it as bolkan or burkan. My Proto-Indo-European origin of Volcanus as a cognate of Germanic die Wolke is more etymologically cogent.

A Modest Apopemptic Passage

Now for the moment we must leave aside the sunder and rupture of earth’s gut, the crust quake, the unsuturing cleft of granitic cones, all such fraught fractures. Instead let us traipse into meadows of lolloping summer, daisy-rich, clover-quilted and bee-choired, to remind ourselves that while this sublunary orb may frighten, it also, as summer is acomin’ in, bids fair to delight.

Bill Casselman, May 16, 2017

Text Copyright 2017 by William Gordon Casselman