93 Fun Facts About Volcanoes

What is molten rock called once it has erupted and is flowing across the ground away from a volcano?

Lava is magma that has reached the surface; runny basalt lava can flow for miles, while sticky lava piles up into domes and explosive eruptions.

Which Roman city was buried under ash and pumice when Vesuvius erupted in 79 AD, then lost for nearly 1,700 years?

Pompeii was rediscovered in 1748, and plaster poured into cavities in the ash revealed the shapes of the dead; neighbouring Herculaneum was buried the same day.

The Ring of Fire is a horseshoe-shaped zone of volcanic and seismic activity surrounding which ocean?

The Ring of Fire encircles the Pacific Ocean and is home to about 75% of the world's active and dormant volcanoes. It stretches from New Zealand through Southeast Asia, Japan, Alaska, and down the western coasts of North and South America.

Which volcano towers over the Bay of Naples?

Mount Vesuvius rises about 1,280 metres over the Bay of Naples and last erupted in March 1944, when lava destroyed the villages of San Sebastiano and Massa di Somma during the Allied occupation.

Which Hawaiian volcano is the largest active volcano on Earth by volume?

Mauna Loa holds some 75,000 cubic kilometres of rock, yet Mauna Kea next door is slightly taller; it was considered the largest volcano on Earth until the underwater Tamu Massif was found.

Which type of volcano has broad, gently sloping sides built up by runny lava flows, like the Hawaiian volcanoes?

Shield volcanoes look like a warrior's shield laid on the ground; they are built from fluid basalt that runs far before it cools, which is why the Hawaiian ones are so wide.

Mount St. Helens blew its top on May 18, 1980, killing 57 people, in which US state?

Washington's Mount St. Helens lost 1,300 feet of height in the deadliest eruption in US history; it was set off by the largest landslide ever recorded.

Which 0-to-8 scale, devised in 1982, rates eruptions much as the Richter scale rates quakes?

The Volcanic Explosivity Index (VEI) measures the explosiveness of volcanic eruptions on a scale from 0 to 8. It was devised in 1982 and considers the volume of erupted material, eruption cloud height, and other factors.

Which volcanic rock is so full of gas bubbles that it floats, sometimes forming rafts miles wide at sea?

Pumice is frothy lava frozen mid-foam; in 2006 a yacht crew near Tonga sailed into a pumice raft many miles wide, and the stone is what you scrub your heels with.

Which country has the most volcanoes that have erupted in recorded history?

Indonesia has around 76 volcanoes with eruptions in recorded history, more than any other country; the US Geological Survey ranks Japan second and the United States third.

What is the bowl-shaped hollow at a volcano's summit called, the one you picture lava bubbling inside?

A crater is the summit bowl, usually less than a kilometre across; a caldera is the much larger depression left when a volcano collapses into its emptied magma chamber.

What is a fast-moving avalanche of hot gas, ash and rock racing down a volcano's flank called, the thing that killed Pompeii?

A pyroclastic flow can move at up to 700 km/h and 700°C, which is why nobody outruns one; pyroclastic surges, not lava, killed most of Pompeii and Herculaneum.

The volcanic island of Iceland sits on top of which mid-ocean ridge?

Iceland sits directly on the Mid-Atlantic Ridge, the boundary between the North American and Eurasian tectonic plates. This makes Iceland one of the most volcanically active places on Earth, with eruptions occurring every few years on average.

What steep-sided volcano type, layered from lava and ash, is also called a stratovolcano?

Composite volcanoes (stratovolcanoes) are tall, steep-sided cones built from alternating layers of lava flows, volcanic ash, and other debris. Famous examples include Mount Fuji, Mount Vesuvius, and Mount St. Helens.

What is a lahar?

A lahar is a destructive mudflow or debris flow composed of volcanic material and water. Lahars can travel at speeds over 60 mph and can occur during or long after an eruption when heavy rain mobilizes loose volcanic deposits.

Which tectonic process creates volcanoes when one plate slides beneath another?

Subduction occurs when one tectonic plate is forced beneath another. As the descending plate sinks into the mantle, it releases water that lowers the melting point of the overlying rock, creating magma that rises to form volcanoes.

What is the name for a volcano that has not erupted in a long time but is expected to erupt again?

A dormant volcano is one that has not erupted recently but is considered capable of erupting again in the future. An active volcano erupts regularly, while an extinct volcano is not expected to ever erupt again.

Mount Fuji, the snow-capped cone in countless woodblock prints, is the tallest peak of which country?

Japan's Mount Fuji stands 3,776 metres on Honshu and last erupted in 1707; it is one of the country's three sacred mountains, and hundreds of thousands climb it each summer.

Which 1815 Indonesian eruption, the most powerful on record, caused 1816's 'Year Without a Summer'?

The April 1815 eruption was rated VEI-7, the most powerful in recorded history. It ejected so much ash and sulfur dioxide that global temperatures dropped, causing crop failures and famine across Europe and North America in 1816.

What is the general term for all solid material ejected from a volcano during an eruption?

Tephra is the general term for all fragments of rock and solidified lava ejected into the air during a volcanic eruption. It ranges in size from fine ash (less than 2mm) to large volcanic bombs (over 64mm).

Crater Lake in Oregon was formed by the collapse of which ancient volcano approximately 7,700 years ago?

Crater Lake occupies the caldera formed by the collapse of Mount Mazama after a massive eruption about 7,700 years ago. At 1,943 feet (592 meters) deep, it is the deepest lake in the United States.

What type of lava has a smooth, ropy surface and is named with a Hawaiian word?

Pahoehoe is a type of basaltic lava characterized by its smooth, billowy, or ropy surface. The name comes from the Hawaiian language. In contrast, a'a lava has a rough, jagged surface. Both terms are used worldwide by geologists.

By roughly how much did the 1991 Philippine eruption's sulfuric haze lower worldwide temperatures?

It was the second-largest terrestrial eruption of the 20th century. In the months that followed, aerosols formed a global haze layer and worldwide temperatures fell by about 0.5 degrees C (0.9 degrees F) across 1991 to 1993.

Which volcano is the most active in Antarctica?

Mount Erebus, 3,794 metres high on Ross Island, is Antarctica's most active volcano and has held a persistent lava lake since at least 1972.

Which volcanic Mediterranean island may have inspired the legend of Atlantis?

Santorini (Thera) blew apart around 1600 BC in one of the largest eruptions of the past 10,000 years, leaving a flooded caldera; the drowned Bronze Age island is often linked to Plato's Atlantis.

What is a line of volcanic islands formed as a plate drifts over a fixed mantle plume called?

A hotspot track such as the Hawaiian–Emperor chain forms as a plate drifts over a fixed mantle plume; John Tuzo Wilson proposed the idea in 1963. A volcanic arc instead forms above a subduction zone.

What type of small, steep-sided volcano is built almost entirely from loose fragments like cinders and ash?

The simplest volcano: congealed lava bits piled around a single vent, rarely above 300 metres, often on the flank of a bigger volcano. Parícutin in Mexico is the textbook case.

Which gas is most abundant in volcanic emissions, typically making up over 60% of volcanic gases?

Water vapour is consistently the most abundant volcanic gas, normally making up more than 60 per cent of total emissions.

What is the name of the volcanic phenomenon where lightning occurs within an eruption column?

A dirty thunderstorm (also called volcanic lightning) occurs when lightning is produced within a volcanic eruption plume. The phenomenon is caused by the collision of charged ash particles, rock fragments, and ice crystals within the turbulent eruption column.

Which Caribbean volcano destroyed Saint-Pierre in 1902, killing about 30,000 people in minutes?

Mount Pelée on the island of Martinique erupted on May 8, 1902, sending a pyroclastic flow that obliterated the city of Saint-Pierre and killed approximately 30,000 people within minutes. Only two people in the city survived.

The volcanic rock obsidian is actually a form of what?

Obsidian is a naturally occurring volcanic glass formed when felsic lava cools so rapidly that mineral crystals do not have time to grow. It is typically black, very hard, and breaks with sharp conchoidal fractures, which made it prized by ancient peoples for tools and weapons.

Which Democratic Republic of Congo volcano is famous for the lava lake in its crater?

Mount Nyiragongo's summit crater has held one of the world's largest lava lakes for much of the past century; its unusually fluid, low-silica nephelinite lava drained in 2002 and 2021, flooding parts of Goma.

What is global cooling caused by eruptions injecting sulfur dioxide into the stratosphere called?

A volcanic winter occurs when large eruptions inject sulfur dioxide into the stratosphere, where it forms sulfate aerosols that reflect sunlight and cool the planet. The 1815 Tambora eruption caused the Year Without a Summer in 1816.

The volcanic eruptions that formed India's Deccan Traps coincided with which mass extinction?

The Deccan eruptions ran for roughly 700,000 years across the Cretaceous-Paleogene boundary 66 million years ago. Some scientists once blamed them for the extinction that ended the dinosaurs, but the Chicxulub impact is now seen as the primary cause.

What is a phreatic eruption?

A phreatic eruption (steam-blast eruption) occurs when groundwater is heated by magma or hot rock and flashes to steam, causing an explosive eruption. No new magma reaches the surface — the eruption ejects only pre-existing rock, steam, and water. Mount St. Helens had phreatic eruptions before its 1980 main eruption.

Which Icelandic volcano's 2010 eruption caused massive air travel disruption across Europe?

Eyjafjallajökull's April 2010 ash plume closed airspace in about 20 countries and stranded roughly 10 million travellers, the worst air-travel disruption since the Second World War; the jet stream carried the ash into Europe's busiest skies.

What percentage of the Earth's surface is covered by volcanic rock?

Approximately 80% of the Earth's surface — both above and below sea level — is volcanic in origin. The ocean floors are almost entirely made of basalt produced at mid-ocean ridges, and volcanic processes have shaped much of the continental crust as well.

Which rare lava, black when fresh and white after rain, does Ol Doinyo Lengai erupt?

Ol Doinyo Lengai in Tanzania is the only volcano known to have erupted natrocarbonatite, a carbonatite lava, in historical times; it emerges at only about 500°C, looks black, and weathers white within days.

What are underwater volcanic openings that emit superheated, mineral-rich water called?

Hydrothermal vents (also called black smokers or white smokers) are openings on the ocean floor that emit superheated, mineral-laden water. First discovered in 1977 near the Galápagos Islands, they support unique ecosystems based on chemosynthesis rather than photosynthesis.

The Toba catastrophe theory says the supereruption 74,000 years ago caused a volcanic winter of what length?

The Toba catastrophe theory proposed a volcanic winter of six to ten years followed by a 1,000-year cooling episode and a human genetic bottleneck; sediment cores from Lake Malawi show little sign of such cooling.

Which Philippine volcano is famed for its almost perfectly symmetrical cone?

Mayon, in Albay province, is the Philippines' most active volcano and is prized for its near-perfect cone; its 1814 eruption buried the town of Cagsawa, leaving only the church belfry standing.

Which volcanic island emerged off Iceland in 1963 and became a UNESCO World Heritage Site?

Surtsey emerged from the Atlantic Ocean during a volcanic eruption that began in November 1963 and continued until June 1967. The island, named after the Norse fire giant Surtr, has been a pristine natural laboratory for studying ecological succession and was designated a UNESCO World Heritage Site in 2008.

Which magma property, largely set by silica content, most determines whether an eruption is explosive?

High-silica magma is far more viscous and holds more dissolved gas, so it tends to explode; runny low-silica basalt lets gas escape, which is why Hawaiian volcanoes ooze while Cascade volcanoes blow.

What was the estimated VEI rating of the Yellowstone supereruption 640,000 years ago?

The Yellowstone supereruption 640,000 years ago was rated VEI 8, the highest level on the scale. It ejected approximately 1,000 cubic kilometers of material, creating the Yellowstone Caldera. Only a handful of VEI 8 eruptions are known to have occurred in Earth's history.

What fast-moving volcanic flows travel over 100 km and form ignimbrites when they solidify?

Pyroclastic density currents (a term covering pyroclastic flows and surges) can leave massive ignimbrite deposits. The largest in the geologic record travelled over 100 km from their source and deposited hundreds of metres of welded tuff.

Which country is home to the volcano Popocatépetl?

Popocatépetl, whose Nahuatl name means 'smoking mountain', stands 5,426 metres about 70 km southeast of Mexico City and has erupted repeatedly since reawakening in 1994.

Which US state has the most volcanoes?

Alaska holds more than 130 volcanoes, the most of any US state; its Aleutian arc sees an eruption almost every year, and ash from Redoubt's 1989 eruption briefly stalled all four engines of a KLM 747.

Which Colombian volcano's 1985 eruption sent mudflows that buried the town of Armero?

Nevado del Ruiz erupted on 13 November 1985; melting ice sent mudflows racing down its valleys and buried Armero, killing about 23,000 people in Colombia's deadliest natural disaster.

The Hawaiian volcano Haleakalā crowns which island?

Haleakalā rises 3,055 metres on Maui and forms about three-quarters of the island; its summit crater, some 11 km long, is the centrepiece of Haleakalā National Park.

Which type of igneous rock, formed from mafic magma, makes up most of the Earth's oceanic crust?

Basalt is the most common mafic igneous rock, characterized by its dark color and relatively low silica content. It forms the majority of the oceanic crust.

Which 1783 Icelandic eruption's poisonous haze killed about a fifth of the island's people?

Laki's eight-month eruption from June 1783 released some 120 million tonnes of sulfur dioxide; the resulting famine killed roughly a fifth of Iceland's population and half its livestock, and the haze reached Europe.

At which type of plate boundary do plates pull apart to build mid-ocean ridges?

At divergent boundaries plates pull apart and basalt wells up to build mid-ocean ridges such as the Mid-Atlantic Ridge, the setting for most of Earth's volcanic output.

Which New Zealand volcanic island's 2019 eruption killed 22 people, many of them tourists?

White Island (Whakaari), off the Bay of Plenty, erupted on 9 December 2019 while 47 people were on it; 22 died, and the steam-driven blast led to criminal charges against the tour operators.

What are igneous rocks with under 45% silica and high mafic mineral content called?

Ultramafic rocks are igneous rocks with a very low silica content (less than 45%) and are composed primarily of mafic minerals like olivine and pyroxene.

What term describes igneous rocks with 52-63% silica, such as andesite and diorite?

Intermediate rocks have a silica content between 52% and 63%, falling between mafic and felsic compositions. Examples include andesite and diorite.

Which Japanese volcano's sudden 2014 eruption killed 63 hikers near its summit?

Mount Ontake, Japan's second-highest volcano, erupted without warning on 27 September 2014; the steam-driven blast killed 63 hikers near the summit, Japan's deadliest eruption in almost 90 years.

Which Caribbean island lost its capital, Plymouth, to the Soufrière Hills volcano after 1995?

Montserrat's Soufrière Hills volcano awoke in July 1995 and buried the capital, Plymouth, under ash and pyroclastic debris in 1997; two-thirds of the island's people left and the government moved to Brades.

What is the tallest volcano in the Solar System, located on Mars?

Olympus Mons rises about 21 km, roughly 2.5 times the height of Everest, and covers an area about the size of Italy. Weak gravity and a crust that never drifted off the hotspot let it keep growing.

Which Japanese volcano's 1991 eruption killed the volcanologists Maurice and Katia Krafft?

Mount Unzen on Kyushu sent a pyroclastic flow down its flank on 3 June 1991, killing 43 people including the French volcanologists Maurice and Katia Krafft and the American Harry Glicken.

Which 1912 Alaskan eruption, the 20th century's largest, created the Valley of Ten Thousand Smokes?

Novarupta's June 1912 eruption on the Alaska Peninsula was the 20th century's largest, ejecting about 13 cubic kilometres of magma; its ash flow filled a valley later named the Valley of Ten Thousand Smokes.

Which large volcanic caldera lies just west of Naples, around the town of Pozzuoli?

Campi Flegrei is a roughly 12-km-wide caldera west of Naples whose floor rises and sinks by metres in a process called bradyseism; its last eruption, in 1538, built the cinder cone Monte Nuovo.

What eruption type features short, violent bursts of viscous magma, ash columns and pyroclastic flows?

Vulcanian eruptions, named after the island of Vulcano north of Sicily, blast out viscous magma in short, cannon-like explosions lasting seconds to minutes; Sakurajima in Japan produces them hundreds of times a year.

Which dormant volcano is Africa's highest mountain?

Kilimanjaro in Tanzania is a dormant stratovolcano with three volcanic cones; the youngest, Kibo, holds the 5,895-metre summit, Uhuru Peak, the highest point in Africa.

What is a volcanic vent that emits steam and gases, signalling geothermal activity, called?

A fumarole is an opening in the crust that emits steam and gases but no liquid or solid material. The steam forms when groundwater is superheated by hot rock and flashes to vapour as it nears the surface; one that gives off significant sulfur compounds is called a solfatara.

The summit of which Ecuadorian volcano is the point farthest from Earth's centre?

Chimborazo, an inactive 6,263-metre stratovolcano, sits almost on the equator, so Earth's equatorial bulge lifts its summit about 2 km farther from the planet's centre than Everest's.

What name is given to the bulbous lava lobes that form when basalt erupts underwater?

Pillow lava forms when basalt erupts under water and its skin chills instantly into rounded, metre-scale lobes; it makes up much of the upper oceanic crust built at mid-ocean ridges.

What are blobs of molten rock that harden in mid-air during an eruption called?

Bombs are by definition larger than 64 mm across. 'Bread-crust bombs' get their cracked surface when the outside solidifies in flight while the interior keeps expanding.

Which eruption type sustains a high, mushroom-shaped ash column that can reach the stratosphere?

The type is named for Pliny the Younger, whose letters describe the 79 AD eruption of Vesuvius that killed his uncle, Pliny the Elder. Static charge in the rising column often triggers lightning.

Which Chilean volcano, one of South America's most active, rises above the resort town of Pucón?

Villarrica, one of Chile's most active volcanoes, towers over Pucón and has often held a lava lake in its summit crater; its eruption on 3 March 2015 forced thousands to evacuate.

Krakatoa lies in the strait between Sumatra and which other Indonesian island?

Krakatoa sits in the Sunda Strait between Sumatra and Java; since 1927 a new cone, Anak Krakatau ('child of Krakatoa'), has grown inside the caldera left by the old volcano's collapse.

What device do volcanologists use to detect ground vibrations from magma movement?

Seismographs are crucial tools for monitoring volcanoes, as they detect earthquakes and other ground vibrations that can indicate the movement of magma or fracturing of rock below the surface.

Which eruption type occurs when rising magma meets shallow seawater or a lake?

Surtseyan eruptions are phreatomagmatic blasts in which magma meets shallow water and flashes it to steam; far more violent than Strombolian bursts, they build tuff rings and maars rather than tall cones, as at Surtsey in 1963.

Which gas gives many volcanic fumaroles and hot springs their rotten-egg smell?

Hydrogen sulfide, the rotten-egg gas, seeps from fumaroles and hot springs; it is deadly at high concentrations, and volcano observatories track it alongside sulfur dioxide and carbon dioxide.

Which country's highest peak is the volcano Teide, on the island of Tenerife?

Spain's highest peak is Teide, a 3,715-metre stratovolcano on Tenerife in the Canary Islands; its last eruption came in 1909, and Teide National Park is a World Heritage Site.

Which Mexican volcano was born in a farmer's cornfield in February 1943?

Parícutin burst from a cornfield near Uruapan, Michoacán, on 20 February 1943 and grew into a 424-metre cinder cone by 1952, burying the village of San Juan Parangaricutiro.

Which famous volcano in the Philippines had a major eruption in 1991, causing significant global cooling?

The 1991 eruption of Mount Pinatubo in the Philippines was one of the largest and most powerful of the 20th century, injecting a vast amount of aerosols into the stratosphere and causing a measurable drop in global temperatures for several years.

Which eruption type features rhythmic, mild bursts that toss glowing cinders from fluid basalt?

Strombolian eruptions are driven by gas slugs bursting at the vent every few minutes, throwing incandescent scoria in short arcs; the style takes its name from the Aeolian island of Stromboli.

What kind of vent erupts lava along a line, often as a 'curtain of fire'?

A fissure vent is a linear volcanic vent through which lava erupts, usually without any explosive activity. Such a vent often creates a 'curtain of fire' as lava spews out along its length.

Which Indonesian volcano's 2010 eruption killed more than 300 people near Yogyakarta?

Mount Merapi, looming over Yogyakarta on Java, erupted in October and November 2010; pyroclastic flows killed 353 people, among them the mountain's traditional spiritual gatekeeper, Mbah Maridjan.

What is the primary method for monitoring ground deformation around active volcanoes?

GPS receivers and tiltmeters track ground deformation as magma pushes in: Mount St. Helens' north flank bulged outward by more than 100 metres before its 1980 eruption, and Hawaiian volcanoes inflate before erupting and deflate afterwards.

Which European volcano, erupting almost continuously for 2,000 years, is the 'Lighthouse of the Mediterranean'?

Stromboli's small but near-constant bursts light the night sky for sailors, hence 'Lighthouse of the Mediterranean'; its deadliest eruption, on 11 September 1930, killed six people, and a 2019 paroxysm killed a hiker.

Which Cascade volcano is the highest peak in Washington state?

Mount Rainier, a 4,392-metre stratovolcano southeast of Seattle, is Washington's highest peak and carries more glacier ice than any other mountain in the contiguous United States.

Which eruption type violently expels incandescent blocks and pyroclastic flows, often with dome collapse?

The type is named for Mount Pelée in Martinique, whose 1902 eruption ranks among the worst natural disasters in history. A bulging 'Peléan spine' at the summit is often the warning sign of collapse.

Which geothermal feature of volcanic areas periodically expels hot water and steam?

A geyser's rhythm can change or stop entirely as minerals clog its plumbing, after earthquakes, or through human interference. Iceland has piped geyser water to heat greenhouses since the 1920s.

In USDA soil taxonomy, what are the famously fertile soils formed in volcanic ash called?

Andisols are rich in volcanic glass and minerals such as allophane, and cover only about 1% of Earth's ice-free land. Their fertility explains the lush forests on many volcanic islands.

Which Hawaiian goddess of volcanoes lends her name to thin strands of volcanic glass?

Pele, the Hawaiian goddess of volcanoes, is said to live in Kilauea's Halema'uma'u crater; 'Pele's hair' is spun from lava fountains and 'Pele's tears' are the glass droplets that fall with it.

The word 'volcano' comes from the name of an island in which Italian island group?

Vulcano, in the Aeolian Islands north of Sicily, takes its name from Vulcan, the Roman god of fire, whose forge the Romans placed beneath it; the English word 'volcano' dates from the early 17th century.

Which moon of Jupiter is the most volcanically active object in the Solar System?

Io, the innermost of Jupiter's large moons, is kneaded by tidal forces that keep hundreds of volcanoes erupting sulfur and silicate lava; its plumes rise up to 500 km above the surface.

Which spacecraft observed cryovolcanoes on Neptune's moon Triton in 1989?

Voyager 2 flew past Neptune's moon Triton in August 1989 and photographed dark plumes rising about 8 km from its nitrogen-ice surface, the first cryovolcanic activity ever observed.

How many volcanoes did the IAVCEI designate as 'Decade Volcanoes' for special study?

The 16 Decade Volcanoes, named for the UN's International Decade for Natural Disaster Reduction in the 1990s, were chosen for destructive histories near populated areas; they include Vesuvius, Etna, Merapi, Rainier and Unzen.

Roughly what share of the surface of Venus is basalt, pointing to a volcanic past?

About 90% of Venus's surface is basalt laid down as vast lava plains; the even spread of its few impact craters suggests a global volcanic resurfacing event roughly 500 million years ago.

Roughly how many submarine volcanoes, most of them extinct, are estimated to exist worldwide?

More than one million submarine volcanoes are thought to exist, most extinct, though only about 119 are known to have erupted in the past 11,700 years; deep water suppresses explosive steam, so eruptions are detected by hydrophones.

Which Peruvian volcano's sulfur dioxide may have caused the Russian famine of 1601-1603?

Huaynaputina in southern Peru erupted in February 1600, the largest eruption in South America's recorded history; its stratospheric sulfuric-acid aerosols reflected sunlight, and the cold, wet summers that followed brought Russia's famine of 1601-1603.