Volcanos

Question 1

What are the four principal types of Volcano

Answer 1

Cinder Cone

Shield

Composite

Dome

Question 2

What kind of lava conditions are likely to lead to fire fountains

Answer 2

Low silica content, but lots of gas

One of the most spectacular fire fountaining events ever recorded on Kilauea produced a lava spray 580 m high at the Kilauea Iki vent in 1959.

Question 3

What type of lava conditions lead to shield volcanos

Where are they usually found

What is the name for their typical eruption type

Answer 3

Low silica - therefore low viscosity

Shield volcanoes are usually found at constructive (where plates move apart) or tensional boundaries.

Eruption type is Hawaiian

Hawaiian eruptions are the calmest of the eruption types. They are characterized by the effusive emission of highly fluid basalt lavas with low gas contents. The relative volume of ejected pyroclastic material is less than that of all other eruption types. The hallmark of Hawaiian eruptions is steady lava fountaining and the production of thin lava flows that eventually build up into large, broad shield volcanoes.

Question 4

What kind of lava conditions lead to Dome Volcanos

Answer 4

Highly viscous, silica rich, low temperature, low gas (so not explosive)

It solidifies shortly after leaving the vent

Question 5

Why do composite volcanos have that name

Where are they usually found

Answer 5

They are made of alternating layers of lava and ash (in constrast to others made of just lava)

They are usually found at destructive (where two plates are moving towards each other) or compressional boundaries.

Question 6

What is a pyroclastic flow

Answer 6

A pyroclastic flow is a mixture of hot steam, ash, rock and dust.

A pyroclastic flow can roll down the sides of a volcano at very high speeds and with temperatures of over 400°C.

Question 7

What volume of material needs to be emitted to count as a supervolcano

What amount is typical of a large volcano

Answer 7

1,000km³

^c.f.

1 km³ for a typical large volcano

Question 8

How wide is the supervolcano caldera at Yellowstone Park

Answer 8

55 by 80 km

Question 9

In what year was the population of Montserrat evacuated (how many people)

When were the most intense eruptions

Answer 9

11,000 in 1995

The most intense eruptions were in 1997

Despite the evacuations, 19 people were killed by the eruptions as a small group of people chose to stay behind to watch over their crops.

Question 10

What is the name for a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water.

From where does the term come

What is particularly good at creating these flows any why

For kudos, what conditions have created the biggest of these flows

Answer 10

Lahar

It is an Indonesian term

Pyroclastic flows are particularly efficient at generating lahars because they have the capability to melt large quantities of snow and ice in a just few hours.

Lahars can also be generated by the basal melting of glaciers by lava flows. Basal melting of glacial ice in Iceland has produced largest historic lahars, in terms of discharge. These water-rich, glacial outburst floods are called jokulhlaups.

Question 11

What are Cinder Cones properly known as

What eruption type are they associated with

Answer 11

Scoria cones

Strombolian eruptions (although Mafic stratovolcanoes can also do Strombolian eruptions)

(Strombolian eruptions are named from the small volcano-island of Stromboli (image), located between Sicily and Italy. This volcano has been erupting almost constantly for hundreds of years. It erupts irregularly every twenty minutes or so to produce an episodic lightshow that gives rise to its nickname, the “Lighthouse of the Mediterranean”.)

Strombolian activity is characterized by short-lived, explosive outbursts of pasty lava ejected a few tens or hundreds of meters into the air. Unlike Hawaiian eruptions, Strombolian eruptions never develop a sustained eruption column.

Question 12

What are the most common type of volcano (and incidentally, the smallest with heights typically less than 300m)

Answer 12

Cinder Cone

Question 13

How are ‘fire fragments’ better known

What is the Greek name for ash

What is the name used for in modern terminology

Answer 13

Pyroclasts

Tephra (actually its the generic term for any airborne pyroclastic accumulation)

Question 14

What are the three types of pyroclasts (and what are their size scales)

Answer 14

Ash (very fine <2mm)

Lapilli (pea to walnut size 2- 64mm) aka cinders

Blocks and bombs (>64mm)

Question 15

What are the two types of pyroclastic flow

Answer 15

NUÉE ARDENTES – these contain dense lava fragments derived from the collapse of a growing lava dome or dome flow

PUMICE FLOWS – these contain vesiculated, low-density pumice derived from the collapse of an eruption column.

Question 16

Who came up with the name nuee ardente

What does it mean

And what inspired the name

Answer 16

French geologist Alfred Lacroix

It means glowing cloud

He used it to describe the pyroclastic flow at Mt Pelee in 1902.

Question 17

What and When was the last Supervolcano to erupt

Answer 17

Toba, Indonesia 74,000 years ago

Question 18

What type of lava compositions are less fluid

Answer 18

andesitic to rhyolitic lavas

which have high silica content

Because they are less fluid they are most likely to trap gases (o - oh)

Question 19

What type of Basaltic lava is smooth or ropy

What type of lava has fragmented surfaces, rough and spiny with a ‘cindery’ appearance

Which is likely to erupt first from a vent

Answer 19

Pahoehoe (pron. Pa - hoy hoy) lava

and

A’a (pron. ah ah) lava

Pahoehoe is typically erupted first

Pahoehoe is often converted to a’a as lava advances downslope, away from the volcano. (The pahoehoe-to-a’a conversion can be caused by either an increase in flow viscosity, or an increase in the rate of shear.)

Question 20

What type of lava does andesite generally produce

Answer 20

Blocky lava

Its blocky because of the higher viscosity

Question 21

With high silica rich lavas, volcanos tend to explode.

But.. degassed they can release lava, which being viscous doesn’t flow too far from the vent

What kind of structures are created (name the two key ones)

Answer 21

Lava domes

and/or, if there is asymetric flow down one side, the vent can produce an elongated extrusion called called a coulée or a dome flow.

Question 22

How else are composite volcanoes known

What is the average composition overall of composite volcanoes

Answer 22

Stratovolcanoes

Andesitic (although many oceanic stratovolcanoes tend to be more mafic than their continental counterparts.)

Question 23

What is the name for vent openings that allow the escape of volcanic gases

Answer 23

Fumaroles

Question 24

What famous volcano was the first instance of a volcano being created from nothing, to the point of its extinction at a height of 424m

Where is it

Answer 24

Paricutin,

200 miles west of Mexico City

Three weeks before the Paricutin eruption occurred, the people near Paricutin village heard the rumbling noises that resembled thunder, yet they were confused because the skies were clear of clouds. The noises were associated with earthquakes at depth near Paricutin. On February 20, 1943 a farmer, Dionisio Pulido, and his wife were burning shrubbery in their cornfield when they observed the earth in front of them swell upward and crack to form a fissure 2-2.5 m across

Strombolian pyroclastic activity began at the site the following day and by the end of the day it generated a 40-m-high scoria cone. In one week it grew to a height of 100 m from the accumulation of bombs and lapilli, and it was raining down finer fragments that burned and eventually covered the village of Paricutin. The eruption was unusually long for a strombolian eruption, with several eruptive phases occurring over a 9-year period. After about two years of mostly pyroclastic activity the pyroclastic phase began to wane, and the outpouring of lava from the base of the cone became the dominant mode of eruption over the next 7 years. The eruption ceased in 1952. The final height of the scoria cone was 424 m.

Question 25

Composite volcanoes are most associated with which eruption type

Answer 25

Plinian (or Vesuvian) eruptions

These explosive eruption types are named after Pliny the Younger, a Roman statesman who wrote a remarkably objective account of the eruption of Italy’s Mt. Vesuvius.

Question 26

In what year did Vesuvius destroy Pompeii

Answer 26

79 AD

Question 27

Why did some fundamentally basaltic volcanos sometimes have Plinian eruptions (e.g. Hekla in 1947-48)

Answer 27

They can occasionally occur in fundamentally basaltic volcanoes where the magma chambers become differentiated and zoned to create a siliceous top.

Over the past 800 years, Hekla has had a history of generating violent initial eruptions of pumice, lasting a few hours, followed by prolonged extrusion of basaltic lava from the lower part of the chamber.

Question 28

What provides the family name for all vulcanoes

Answer 28

The small Italian island of Vulcano

Historic eruptions led the Romans to believe that this island was the forge of Vulcan, son of Jupiter and blacksmith to the Roman gods

Question 29

What type of eruption is catagorised by canon-like short lived eruptions of bombs and blocks, as if clearing the throat for relatively quiet and sustained eruptions

Answer 29

Vulcanian

These eruptions are often associated with growing lava domes, such as that at Mt. Pelée in 1902

Question 30

What type of eruptions are generated by the intereaction of magma with either groundwater or surface water.

What in particular is the name for the basaltic lava types. What eruption (and year) is it named after

What is the name for particularly big versions (order of magnitude larger)

Answer 30

Hydrovolcanic eruptions

Surtseyan (the really large ones are called Phreatoplinian eruptions)

Named after the Iceland Surtsey eruption of 1963

Surtseyan eruptions are considered to be the “wet” equivalents of Strombolian-type eruptions, although they are much more explosive.

(When the volcanic island of Surtsey was born in the Atlantic, the initial hydrovolcanic eruptions were spectacularly explosive. As the volcano grew, however, the rising lava in the central vent interacted with water to a lesser degree, so that the waning stages of the eruption became more Strombolian in character.)

Question 31

In what year was the Krakatoa eruption

Answer 31

26-27 August 1883

Question 32

What Icelandic volcano poured out 14 km³ of basaltic lava and clouds of poisonous gas, killing (by famine) about 25% of Iceland’s population, and possibly upto 6 million globally

Answer 32

Laki

A fissure eruption in 1783-84

The eruption, is also known as the Skaftáreldar (“Skaftá fires”)

The outpouring of gases, including an estimated 8 million tons of hydrogen fluoride and an estimated 120 million tons of sulfur dioxide, gave rise to what has since become known as the “Laki haze” across Europe.

Question 33

What is the Supervolcano in California

Answer 33

Long Valley Caldera

Question 34

What is the name of Korea’s highest mountain - also a potential sub-supervolcano

Answer 34

Mount Paektu

In 946 AD, the eruption of Mount Paektu, Korea’s highest mountain, blasted 96 cubic kilometres of debris into the sky, 30 times more than the relatively puny 3.3 cubic kilometres that Vesuvius spewed over Pompeii in AD 79.

Question 35

What was the name of the Icelandic volcano which produced an anti-holiday maker ash clound in 2010

Go for it!!

Answer 35

Eyjafjallajokull

pronounced (Ay-a-fiat-la-yur-cook [then a sound like saying key in an electronic way])

Question 36

When did Mt Pinatubo erupt

How many km³ did it eject (how approx. does this compare with Vesuvius and Mt St Helens)

Answer 36

15 June 1991

It was the 2nd largest eruption of the 20th century

10 km³ of magma were evacuated (about 3x the amount of Vesuvius, and 10x larger than Mt St Helens)

Question 37

What was the biggest eruption of the 20th century (when and where)

how does this compare with the two biggest of the 19th century (which were… when and where)

Answer 37

Novarupta (Alaska) - 17 km³

Karakatoa (Indonesia) - 1883 - 20 km³

Tambora (Indonesia) - 10 April 1815 - 160km³