Volcanism Flashcards
1
Q
What are volcanoes?
A
Fissures at the Earth’s crust that allow hot, molten rock and gasses to escape at the surface
2
Q
What can volcanic activity form?
A
Mountains or features like mountains over millions of years (Ma)
3
Q
What does a volcano start with?
A
It starts with a fissure and builds up
4
Q
Which volcanoes are the most dangerous on Earth?
A
Indonesian volcanoes`
5
Q
What can subduction of a plate lead to?
A
Volcanoes
6
Q
Why doesn’t lava flow very far?
A
Because of its viscosity
7
Q
What was a secondary effect of the collapse of a dome of Anak-Krakatau?
A
It triggered a tsunamii
8
Q
What is needed in order to prepare for tsunamis?
A
Effective warming systems
9
Q
How can tsunamis differ?
A
This depends on if they were triggered by earthquakes or volcanoes
10
Q
How many died when Anak Krakatoa erupted in 2019?
A
At least 430
11
Q
How many were injured when Anak Krakatoa erupted in 2019?
A
1495
12
Q
How far away is Mexico City from Colma?
A
483km
13
Q
When did Colma erupt?
A
29th January and 1st February 2016
14
Q
How far did the ash plumes from Colma rise in 2016?
A
4.6-6.7km
15
Q
How many active volcanoes are on Earth?
A
1500
16
Q
How many volcanoes have erupted in the last century?
A
400
17
Q
On average how many eruptions are there each year?
A
50
18
Q
Where is most volcanic activity concentrated?
A
Along major plate boundaries
19
Q
What do the risks of volcanoes depend upon?
A
The type of volcano
20
Q
How many people live near volcanoes?
A
Around 500million
21
Q
How many volcano related deaths have their been during the last 125 years?
A
100,000
22
Q
How many volcano related deaths have there been in the last 20 years?
A
23,000
23
Q
Where are some densely populated countries located?
A
In volcanic zones
24
Q
Where are some major cities with over 350,000 people located?
A
Near volcanoes
25
What can dust from volcanoes cause?
Lightning
26
In which direction does lava flow?
Downhill only
27
What happens to the ash plume in the sky after an eruption?
It eventually collapses
28
In which direction can pyroclastic flow flow?
Uphill as well as downhill
29
What does the type of volcano depend upon?
The type of magma
30
When have most volcanoes present today been active?
During the quaternary
31
What can volcanoes interact with?
The plate boundary
32
What is one of the first recognised eruptions?
Vesuvius 79AD
33
What happened when Tambora erupted?
There was a year without summer
34
Why did Tambora cause cooling?
The ash particles blocked some sunlight
35
When did Mount St Helen erupt?
1980
36
When did Soufriere erupt?
1995
37
When did Vesuvius erupt?
79AD
38
When did Unzen erupt?
1991
39
When did Krakatoa erupt?
1883
40
When did Villarica erupt?
1963-1964
41
When did Mount Pelee erupt?
1902
42
When did Tambora erupt?
1815
43
What was a problem when Mount St Helens erupted?
The US was not prepared for any type of eruption
44
What 3 things control magma explosivity?
Magma composition
Viscosity of magma
The amount of dissolved gas that the magma contains
45
What happens if magma contains lots of gas?
It is more explosive
46
What happens if the magma flows (is quite runny)?
It is less dangerous due to its low viscosity
47
What happens as magma cools?
It crystalises
48
What is an issue when magma crystalises?
Some minerals are explosive
49
What happens to the minerals as they crystalise?
Their composition changes
| Different minerals or elements at different temperatures
50
What is the continuous reaction series?
Minerals don't change just the elements present
51
What is the discontinuous series?
The minerals change as the temperature changes
52
What is olivine rich in?
Calcium
53
What are characteristics of quartz?
Very viscous and explosive
54
What happens to the magma as it flows over a continent?
Its composition changes because it is melting other rocks
55
What is on the continuous branch?
Calcium-rich
Plagioclase
Sodium-rich
56
What is on the discontinuous branch?
Olivine
Pyroxene
Amphibole
Biotite
57
Put intermediate, mafic and felsic in order from high temp to low?
Mafic
Intermediate
Felsic
58
What is felsic magma like?
High viscosity
59
What is mafic magma like?
Low viscosity
60
What does the Bowen reaction series show?
Magma composition
| It looks like a Y
61
What does magma viscosity change with?
Temperature
62
What happens to the explosivity as the magma gets more viscous?
More viscous= more elasticity
63
What are pillow lavas on continents evidence of?
Mid-oceanic ridges
64
What is the thermodynamic equilibrium of magma?
Mineral cooling and crystalisation
65
Why does a magma reaction series take place?
The earlier formed crystals react with the melt to form new crystals
66
What are the two series that the common minerals of igneous rocks can be divided into?
Continuous reaction series of feldspars
| Discontinuous reaction series of ferromagnesian minerals
67
What does the reaction series imply?
From a single parental magma, various kinds of igneous rocks can be derived by magnetic differentiation
68
What does high viscosity mean?
There is a great resistance to flow
69
What happens to the lavas when temperatures are high?
The lavas are more fluid
70
What happens to the lava as it cools?
It becomes more viscous
71
What are basaltic lavas like?
They are quite fluid and can therefore are thin and can travel long distances
72
How far can lava travel?
150km
73
What are the 3 volcanic landforms from basaltic magma?
Sheild volcanoes
Basalt plateaus
Cinder cones
74
What is the silica content of basalt like?
It is low, less than 50%
75
What is the explosivity of basaltic magma like?
Least explosive
76
What is the gas content of basaltic lava like?
It is small, less than 2%
77
What are the characteristics of pillow lavas?
Basaltic
| Elongated interconnected flow lobes that are elliptical or circular in cross section
78
What is pahoehoe?
This is the second most abundant type of lava
79
What is pahoehoe characterised by?
A smooth, billowy or ropy surface
80
What is the thickness of pahoehoe flows like?
It tends to be relatively thin
81
What are Aa lavas characterized by?
A rough, jagged, spinose and generally clinkery surface
82
What is the thickness of aa lava flows like?
Relatively thick compared to pahoehoe flows
83
What is the thickness of rhyolitic flows like?
They are quite thick because of their viscosity, therefore they travel short distances
84
What is the silica content of rhyolitic magma like?
It is high, over 70%
85
What is the viscosity of rhyolitic magma like?
High
86
What is the gas content of rhyolitic lava like?
It is high, over 4%
87
What is the tendency for ryholitic lava to explode?
Greatest
88
What two volcanic landforms are formed by rhyolitic magma?
Volcanic domes
| Pyroclastic flows
89
What is the silica content of andesitic magma like?
Intermediate about 60%
90
What is the viscosity of andesitic magma like?
Intermediate
91
What is the gas content of andesitic magma like?
Intermediate
92
What is the tendency to explode for adesitic lava?
Intermediate
93
What are two volcanic landforms that are created by andesitic magma?
Composite cones
| Straovolcano
94
What do gases in magmas do?
They migrate upwards and expand during the migration of the magma
95
What creates lava fountains?
These are created when gases in magma migrate upwards and escape from the vent
96
What happens to gases in viscous magmas?
They expand during their migration upward of the magma which they do with difficulty. The pressure of gases and magma increases and leads to volcanic eruptions which eject semi-molten rocks and hot gases
97
What can be found in rhyolitic lava flows?
Quartz
98
What can be used to date land surfaces?
Pyroclastic flows
99
What are the 6 types of volcano?
```
Fissure
Shield
Dome
Ash-cinder
Composite
Caldera
```
100
What is the slope of a fissure volcano like?
It is gentle and made of basaltic lava
101
What is the slope of a dome volcano like?
It is a steep convex slope from thick, fast cooling lavas
102
What is the slope of an ash-cinder volcano like?
It has layers of ash and cinder
103
What is the slope of a shield volcano like?
It is low-angle and built by successive layers of low viscosity lava
104
What is the material from a shield volcano like?
Only 10% of the erupted material is explosive
105
Where do shield volcanoes tend to form?
At hot spots or in back-arc volcanic settings
106
What are stratovolcanoes like?
They have a steep conical edifice built by the alternation of lava flows and pyroclastic deposits
107
What does the associated magma generally contain for stratovolcanoes?
Up to 10% volatiles and highly viscous
108
What type of eruption occurs at a stratovolcano?
Explosive eruption
109
What are 8 eruption products?
```
Plume
Eruption column
Bombs
Pyroclastic flow
Lava flow
Lahar
Acid rain
Ash fall
```
110
What is lahar?
Mud or debris flow
111
What are fumaroles?
Openings near volcanoes through which gases escape
112
What causes lahars to form?
When pyroclastic flows or lahars mix with ice or water
113
What is the flow of lahars like?
Fast
114
When do caldera volcanoes occur?
When the volcano collapses in on itself after an eruption
115
What is the viscosity like at dome volcanoes?
Quite viscus
116
What happens to eruptions at volcanoes?
They don't stay constant, the change and evolve
117
What occurs when a doe collapses?
Pyroclastic flow
118
How is eruption classified?
By explosivity
119
What is VEI?
Volcanic Explosivity Index
120
What does a VEI score of 0 show?
Non-explosive
121
What does a VEI of 1 show?
Small
122
What does a VEI of 2/3 show?
Moderate
123
What does a VEI of 4 show?
Large
124
What does a VEI of 5/6 show?
Very large
125
What is the VEI scale?
0-8
126
What are the characteristics of a stombolian eruption?
Rhythmic ejection of incandescent cinder, lapilli and bombs to heights of 10-100m
127
What are stombolian eruptions usually caused by?
Basaltic or andesitic lavas
128
What is the eruption rate of strombolian eruptions?
Less than 200 m/s
129
What are the characteristics of a vulcanian eruptions
e.g. Colima, Mexico March 10th 2005
5km high ash cloud
Several pyroclastic flows
Ash and rock fragments as far as 12km
130
What is the size of the eruption column for plinien eruptions?
20-40 km
131
What is the ejection velocity for plinien eruptions?
100-400 m/s
132
What is a characteristic of plinien eruptions?
Bubbles and viscus magma rapidly ascent together, rapid decompression leads to fragmentation and increase explosion
133
What are the 7 types of eruption?
```
Hawaiian
Strombolian
Sub-plinian
Vulcanican
Surtseyan
Ultraplinian and plinian
Phreatoplinian
```
134
What is the height of the eruption column for hawaiian eruptions?
Less than 2km
135
What is the height of the eruption column for strombolian eruptions?
Less than 10km
136
What is the height of the eruption column for vulcanian eruptions?
Less than 20km
137
What is the height of the eruption column for surtseyan eruptions?
Less than 20km
138
What was the height of the eruption column for ultraplinian and plinian eruptions?
Less than 55km
139
What is the height of the eruption column for phreatoplinian eruptions?
Less than 40km
140
Which is more explosive, phreatoplinian or ultraplinian and plinian?
Phreatoplinian
141
What separates vulcanian and surtseyan eruptions?
Their explosivity, surtseyan is more explosive
142
What type of eruption was Vesuvius in 79AD?
Plinien
143
How high was the eruption column for Vesuvius?
33km high
144
What was the rate at which hot ash and pumice fell on Pompeii at for Vesuvius?
Hot ash and pumice fell onto Pompeii at a rate of 12-15cm an hour
145
What areas did ash and pumice from Vesuvius cover?
Pompeii
Herculaneum
Stabiae
146
At what time was there total darkness after Vesuvius erupted?
1pm
147
When was Pompeii buried until?
It was buried until excavations began in 1748
148
Which large city is located near to Mount Vesuvius?
Naples
149
What was the VEI for Mount St Helens in 1980?
4
150
When did Mount St Helens erupt?
18th May 1980
151
What happened just before Mount St Helens erupted?
There was a 5.1 magnitude earthquake
152
How many miles upward did the erupted material from Mount St Helens rise?
16 miles
153
What are supervolcanoes?
These are volcanoes that spread ash much further than normal volcanoes
154
Why do supervolcanoes exist?
They have massive magma chambers that can eject much more material
155
Where can supervolcanoes be found?
Above hotspots
156
What causes the magma chamber of the supervolcano to grow?
Partial melting of the asthenosphere.
157
What happens as the supervolcano's magma chamber grows?
The magma becomes under high pressure and the surface bulges and cracks. The Earth's strained surface eventually starts to shatter
158
What happens once the supervolcano has caused the Earth to shatter?
Large, explosive eruptions take place and there are numerous pyroclastic flows
159
What happens after a supervolcano eruption?
A crater-like depression forms called the caldera
160
What is a caldera?
Crust that collapses in an empty magma chamber
161
What are 8 volcanic hazards?
```
Lava flows
Pyroclastic flows
Ash falls
Lahars
Landslides
Fine ashes in the air and on the ground
Volcanic gases
Climate change
```
162
What can latitude affect?
Scale
163
What can ash in the lower stratosphere lead to?
Ash in the lower stratosphere can lead to warming of the stratosphere and cooling of the troposphere
164
What is tephra?
This is ash- any airborne pyroclastic
165
What is ash?
Very fine-grained fragments, generally dominated by broken glass shards but can also contain rock fragments
166
What is the size requirement for ash?
Less than 2mm
167
What is lapiilli?
Pea to walnut-size pyroclasts
168
What is the size requirement for lapilli?
2-64mm
169
What do lapilli often look like?
Cinders
170
What causes accretionary lapilli?
In water-rich eruptions, the accretion of wet ash may form rounded spheres
171
What is the size requirement for blocks and bombs?
Over 64mm
172
What are blocks?
These are ejected as solid fragments with angular shapes
173
What are bombs?
These are ejected as incandescent lava fragments which were semi-molten when airborne and therefore inherited streamlined, aerodynamic shapes
174
What causes pyroclastic flow?
This occurs when the mixture of hot gas and rocks are heavier than the surrounding air, causing the plume to collapse in on itself and flow down the slope of the volcano
175
At what speed do pyroclastic flows move?
Over 100km/hr
176
Where are pyroclastic flow deposits usually confined to?
Valleys
177
What temperatures can pyroclastic flows reach?
Over 400C
178
What are lahars composed of?
Water, and sediment
179
What percentage of sediment in a lahar makes it turbulent?
20-60%sediment= turbulent
180
What percentage of sediment in a lahar makes it smooth?
More than 80% sediment
181
Which type of lahar moves faster?
The smooth lahar is faster than the turbulent lahar
182
What can happen to the glaciers and snow caps at the top of the volcano?
They can suddenly melt
183
How fast can melted snow move downslope?
50km/hour
184
How far can melted snow move downslope?
It has a long flowing distance, tens of miles from volcanoes
185
What are landslides?
Large masses of earth that fall, slide or flow rapidly
186
Why are volcanic edifices prone to instability?
Many volcanoes are steep-sided mountains, often partly constructed from poorly consolidated volcanic deposits
187
What was the VEI of Krakatoa in 1883?
VEI 6
188
How many fatalities were there in Krakatoa in 1883?
120,000 or more
189
How high was the Krakatoa 1883 tsunami?
46m
190
What happened to the island of Krakatoa in 1883?
It had almost entirely disappeared but it has been growing ever since
191
Why does the stratosphere warm after an eruption?
The particles in the atmosphere that have been ejected by the volcano absorb the radiation
192
Why does the troposphere cool after an eruption?
As the stratosphere absorbs more radiation, less gets to the sun
193
What can a strong, brief impact on climate change be useful for?
It can help to make better predictions of future climate and weather
194
How long can the strongly enhanced reflection of incoming solar radiation cause global cooling at the surface for?
2-3 years
195
What effect (greenhouse or haze effect) is more greatly enhanced by volcanic eruptions?
The haze effect is more affected than the greenhouse effect
196
What does the haze effect cause?
Short term cooling
197
What happens to cause the haze effect?
Sulfur combines with water vapour in the stratosphere to form a dense cloud of sulfuric acid droplets which take year to settle out and they cool the troposphere because they absorb solar radiation and scatter it back to space
198
How can volcanic eruptions enhance the greenhouse effect?
The add CO2
199
Which is a larger input of CO2 into the atmosphere: humans or volcanoes?
Human activities put more CO2 into the atmosphere each year
200
When did the Laki eruption occur?
1783-1784
201
Where was the Laki eruption?
Iceland
202
What percentage of livestock was killed by the Laki eruption?
75%
203
What percentage of Iceland's population was killed?
24%
204
What was the volume of the lava for the Laki eruption?
14.7 km3
205
What was the volume of tephra at the Laki eruption?
0.4 km3
206
What climate impacts were there as a result of the Laki eruption?
Summer of 1783 was extremely warm over Europe
| Winter of 1783-4 was extremely cold over Europe and North America
207
What are circulation anomalies produced by?
Volcanic gases and aerosols
208
Anomalies from which aerosols caused the haze effect?
Sulphate aerosols
209
What two volcanic gases (not aerosols) act as gases?
CO2 and SO2
210
When was the Tambora eruption?
1815
211
What percentage of people died on Sumbawa?
35%
212
What was the VEI of Tambora?
7
213
What did the Tambora eruption cause?
The year without a summer
214
When was the ultra-plinian eruption of Pinatubo?
1991
215
What was the VEI of the Pinatubo 1991 eruption?
VEI5
216
What effect did the Toba super-eruption have on climate?
A drop of 10C globally for a few months, cooling lasting several decades
6 years of volcanic winter, followed by 1000 years of the coldest, driest climate of the late Quaternary
