Volcanoes Flashcards

Question

Flank

Answer 1

often refers to the sides of the volcano

Answer 2

a narrow opening or crack along which magma erupts often on a volcano’s flanks

Answer 3

opening through which volcanic gases emerge

Answer 4

are characterized by the outpouring of basaltic lava onto the surface (e.g. Kilaeua, Hawaii). These eruptions tend to be non-explosive because steam bubbles in the rising mafic magma are able to expand and burst

Answer 5

are characterized by the violent fragmentation of magma (e.g. Mount St. Helens, WA, 1985). These eruptions are explosive because the high viscosity of intermediate or felsic magmas do not allow trapped steam bubbles to escape leading to an increase in pressure. The main products of explosive eruptions are referred to as tephra (unconsolidated) or pyroclastic deposits (consolidated).

Answer 6

Named for the resemblance to a warrior’s shield Largest volcanoes on Earth with gently sloping sides (<5-10°) and broad summits The shape is created from fluid basaltic lava that pours out in all directions from the central summit Formed mostly from effusive eruptions (contains very little tephra) Lavas also commonly erupt from vents along fractures (rift zones) that develop on the flanks of the volcano (e.g. Pu’u ‘O’o’ cinder cone on Kilauea, Hawaii)

Answer 7

Also referred to as stratovolcanoes Characterized by a steep, conical shape (6-10° on flanks to 30° near top) Built mostly from tephra (up to 50%) but characterized by both effusive and explosive eruptions leading to the interlayering of lava flows and tephra Owing to the higher viscosity of felsic magmas, they are usually more explosive (and dangerous) and erupt less often than shield volcanoes Characterized by long periods of repose or inactivity lasting for hundreds or thousands of years

Answer 8

These are steep-sided small volume cones (<300 m) with a round to oval surface and a crater on the top that often occur in association with shield volcanoes They form from the accumulation of pyroclastic debris, usually cinders or scoria Cinders or scoria form when basaltic or andesitic magma containing abundant volatiles is thrown out explosively from the volcanic vent

Answer 9

Cinder cones typically are monogenetic (erupting only once) and therefore have short life spans (decades)

Answer 10

Scoria is recognizable from its texture of abundant cavities produced from expanding steam bubbles called vesicles

Answer 11

Volcanic domes are steep-sided mounds of lava that form around vents from the eruption of highly viscous high volatile felsic magmas (rich in silica) such as rhyolite and dacite Lava piles up near vent, forming a very rough, spiny dome over the vent that is pushed up from magma below Very dangerous as domes may produce lateral blasts (e.g. Mount St Helens, 1980) or pyroclastic flows

Answer 12

Less than 1 km in diameter Circular to oval depressions at the top of volcanoes that form by the explosive ejecta of magma or from collapse when magma is withdrawn from a shallow magma chamber

Answer 13

Larger than >1km usually several km in size Circular to oval depressions at the top of volcanoes that form by the explosive ejecta of magma or from collapse when magma is withdrawn from a shallow magma chamber

Answer 14

openings at the summit or flanks of the volcano where lava erupts or tephra or pyroclastic debris is ejected

Answer 15

Some vents are circular and others form along linear cracks known as fissures or rift zones

Answer 16

are >24 km in diameter that produce more than 1000 km3 of ash and fragmented rock Produce super eruptions that are larger than any eruptions known in historic times

Answer 17

originate when large volumes of magma rise to shallow depths in the crust above a mantle hot spot; pressure then builds until the eruption occurs Supervolcanoes are associated with the eruption of large volumes of felsic magma at continental hotspots

Answer 18

are broad low relief craters that have formed by the violent interaction of magma and groundwater that form a crater by violent explosion (phreatic eruptions Often fill with water along with craters and calderas to form crater lakes

Answer 19

Crater lakes may be deadly if a breach in the crater wall produces a lahar (Mount Ruapehu, New Zealand) or when they produce limnic eruptions in which dissolved CO2 suddenly erupts from deep later water formed by filling of water in maars, craters, and calderas

Answer 20

produced by extensive fissure eruptions over millions of years that result in thick, nearly horizontal lava flows covering thousands of km2 (e.g. North Mountain Basalt, Nova Scotia)

Answer 21

Many volcanoes erupt subglacially Water leaks from the lake into the volcano below, destabilizing the magma and resulting in pyroclastic debris explosively ejected by hydrovolcanic eruptions Eventually the volcano breaks through the glacier surface and basaltic lava erupts to form the flat-topped tuya

Answer 22

Tuyas form when a basaltic eruption melts part of the overlying ice and produces pillow basalt in the subglacial lake In British Columbia, there is evidence of tuyas that were developed between 10,000-740,000 years ago

Answer 23

Shield volcanoes are typically found along divergent plate boundaries where crust is pulling apart (Iceland, East African Rift, Basin and Range) or oceanic hotspots

Answer 24

Stratovolcanoes occur above subduction zones; lava dome collapse often occurs in final stages of activity

Answer 25

Cinder cones may occur in a variety of settings- commonly in association with or on the flanks of larger volcanoes

Answer 26

Most active volcanoes are located near plate boundaries 2/3 of all active volcanoes on land are located along the Ring of Fire surrounding the Pacific Ocean 50 to 60 volcanoes erupt each year Most eruptions are in sparsely populated areas Nearly 100,000 people have been killed by eruptions in the past 100 years 500 million people live in the vicinity of volcanoes Active volcanic regions around the world include Japan, Mexico, Philippines, and Indonesia Western North America cities with populations of more than 100,000 include Vancouver (Mt Baker), Seattle and Tacoma (Mt Rainier), and Portland (Mt Hood)

Answer 27

First extensively documented volcanic eruption by Pliny the Younger (16,000 killed)

Answer 28

Devastating link between tsunami and volcanic eruptions (36,000 killed)

Answer 29

Devastating link between lahars and volcanic eruptions (23,000 killed)

Answer 30

Lessons learned regarding volcano forecasting (60,000 evacuated; 300 killed)

Answer 31

The Volcanic Explosivity Index (VEI) outlines several types of magmatic volcanic eruptions and quantifies their eruption size, volume, and strength Styles of eruptions can range from frequent and mild (predominantly effusive) to infrequent and violent (predominantly explosive) Styles are often named after famous volcanoes that exhibit a principal type of behaviour Some volcanoes change style over the duration of one eruptive event yet others will exhibit the same style over several eruptive events

Answer 32

defined by the VEI based on their eruptive mechanism and strength

Answer 33

non-magmatic eruptions, driven by the superheating of steam in contact with magma (sources of water may include non-volcanic lakes, crater lakes, or shallow seas) produces maars

Answer 34

steam-driven explosions arising from the interaction of magma with ground water hazards include ash falls and base surges

Answer 35

very mild effusive eruptions characterized by lava flows (low silica, volatiles, viscosity) Produces shield volcanoes Occur at cinder cones

Answer 36

mildly explosive eruptions characterized by the production of cinder or scoria Produced from the interaction of fluid magma (intermediate viscosity) with ground or sea water Occur at cinder cones such as Paricutin, Mexico and typically at stratovolcanoes (e.g. Mt. Etna and Stromboli, in Italy)

Answer 37

more explosive than Strombolian eruptions due to andesitic to dacitic type magmas (high silica, volatiles, viscosity) Produces small/several lava domes and collapse Occur at stratovolcanoes such as Sakurajima, Japan; famous example is Nevado del Ruiz, Columbia (1985)

Answer 38

characterized by devastating pyroclastic flows and a larger eruption column than seen in Vulcanian events Named for the 1902 eruption of Mount Pelée in Martinique Produces a much larger lava dome and collapse Occur typically at stratovolcanoes such as Mayon Volcano, Philippines; Iceland (2010)

Answer 39

highly explosive eruptions produced from dacitic to rhyolitic magmas (high silica, volatiles, viscosity) that generate massive ash fallout in addition to pyroclastic flows Prevailing winds drive the eruptive column of gases, ash, and fragments away from the volcano (ashfall) covering regions from 0.5-50 km3 in size Pyroclastic flows are generated at speeds up to 700 km/hr and extending hundreds of kilometers from the vent Hot materials ejected from the summit may mix with snowfall, ice, and other volcanic deposits to form lahars Named for Pliny the Younger who documented the A.D. 79 eruption of Mount Vesuvius, Italy Occur typically at stratovolcanoes; famous examples include Mt St. Helens, WA (1980), Hekla, Iceland (1947-1948), Mt. Pinatubo, Phillippines (1991)

Answer 40

An eruptive column is produced in the magma chamber due to the build-up of pressure propelling magma up and out of the volcanic vent into the stratosphere

Answer 41

Same as Plinian characteristics but produce a much greater volume of eruptive materials (e.g.) Toba, Indonesia, 740,000 years ago

Answer 42

People live near volcanoes for a variety of reasons Place of birth On some islands, all land is volcanic Fertile land for farming Believe an eruption is unlikely Unaware of risk Economic limitations

Answer 43

Relatively low levels of volcanic activity and the remoteness of Canadian volcanoes has resulted in a general false perception that Canada’s volcanoes are extinct Historic records in Canada (since 1867) are short in comparison to other regions of the world, however Indigenous oral traditions extend much farther back than the written record Volcanoes have much longer lifespans than humans; they are generally active over thousands of years

Answer 44

currently erupting, showing signs of unrest, or has erupted in historic time

Answer 45

not currently active but could become restless or erupt again

Answer 46

unlikely to erupt again, however keep in mind this is difficult to determine

Answer 47

200 potentially active volcanoes in Canada 49 have erupted in the past 10, 000 years

Answer 48

lava flows, ashfalls, volcanic bombs, pyroclastic flows and surges, lateral blasts, and poisonous gases

Answer 49

lahars, debris avalanches, landslides, groundwater and surface contamination, floods, fires, and tsunamis

Answer 50

global cooling, famine, disease

Answer 51

hazardous processes associated with volcanoes travel at a few km/hr devastating in populated regions lava flows may have durations of many years

Answer 52

Smooth, hummocky, or ropy surface that forms as fluid lava drags cooled skin on the surface into small wrinkles and folds Higher in temperature and volatiles but less viscous than aa flows May develop lava tubes

Answer 53

Rubbly surface composed of broken partially crystallized blocks called clinkers Lower in temperature and volatiles but higher in viscosity; thus are much thicker and slower than pahoehoe flows

Answer 54

Lava tubes: develop when the surface of a pahoehoe flow solidifies but molten lava continues to flow in a channel beneath Often consist of a main tube with several small tubes that supply lava to the front of one or more separate lava flows Lava tubes may transport lava up to several km from the vent

Answer 55

1) Bombing 2) Hydraulic Chilling 3) Wall Construction

Answer 56

Thick stubby flows of andesite, dacite, or rhyolite that do not travel far from volcanic vent because of high viscosity Hazardous because they induce pyroclastic flows due to lava dome collapse (Vulcanian, Peléan , and Plinian style events)

Answer 57

general term for any fragments of rock and ash blasted into the air

Answer 58

tephra and gases downwind of the volcano

Answer 59

tephra and gases directly above volcanic vent

Answer 60

<2 mm fragments

Answer 61

2-64 mm fragments

Answer 62

>64 mm fragments

Answer 63

Reduction in visibility/causes darkness and atmospheric haze ``` Buildings may be damaged as tephra piles up on roofs Health hazards (respiratory illnesses) ``` Mechanical and electrical equipment can be damaged disrupting electrical power Aircraft engines can experience failure (e.g. 1989, Mt Redoubt, Alaska; 2010 Eyjafjallajökull, Iceland)

Answer 64

Atmospheric haze (causing brilliant sunsets) Surface water may be contaminated Damage to prime agricultural lands (famine) Contributes to temporary global cooling (e.g. Laki 1783; Tambora, 1815; Krakatau, 1883; Pinatubo, 1991)

Answer 65

Produced the 2 largest ashfall deposits in the past 2,000 years East lobe was produced 1149 years BP and north lobe was produced 1887 yrs BP from Mt Bona-Churchill, in Alaska Ash from the east lobe eruption was dispersed from 25 km west of the Alaska-Yukon border to Great Slave Lake, NWT

Answer 66

avalanches of hot rock, ash, volcanic rock fragments Can move at speeds up to 150 km/h

Answer 67

dense clouds of hot gas and rock debris produced by explosive interaction of water and magma Can move at speeds of more than 360 km/h Due to their speed surges are better able to overtop topographic barriers and cross bodies of water than pyroclastic flows

Answer 68

Rock fragments, gas, and ash that are blown horizontally from side of volcano, mixing with avalanche deposits that sweeps down the side of the volcano and reaches up to 25 km away Poisonous Gases Edifice or Sector Collapse Debris Flows and Other Mass Movements - Lahars (volcanic ash + pyroclastic material become saturated with water and rapidly move downslope.) Tsunami Interactions with Snow and Ice (CREATES LAHARS)

Answer 69

Magma chambers may leak gas into overlying crater lakes or limnic eruptions may occur Volcanoes release sulphur dioxide which mixes with water to form acid rain and “vog” (a type of smog) Volcanoes also release fluorine which may contaminate pastures affecting livestock

Answer 70

Lahar is an Indonesian term for a mudflow or debris flow that originates on the slope of a volcano Secondary effect when lahars occur days, weeks or years after an eruption

Answer 71

Volcanic eruptions that occur subglacially or near glaciers produce jökulhaups Jökulhaup is an Icelandic term for any sudden burst of water released from subglacial lakes or reservoirs Jökulhaups may be triggered by melting of snow and ice from a volcanic eruption or geothermal heating Iceland is at the greatest risk from these types of eruption-triggered floods

Answer 72

Shallow earthquakes can precede eruptions | May not provide enough time for evacuation

Answer 73

Accumulation of hot magma changes temperatures, magnetic properties, and chemical properties of rocks and groundwater

Answer 74

Monitoring the growth of bulges or domes

Answer 75

Changes in carbon dioxide and sulphur dioxide emission rates may indicate movement of magma toward the surface

Answer 76

Mapping of lava flows and pyroclastic deposits can be helpful in predicting future eruptive behaviour