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Leaving Cert Geography - > Volcanic Activity > Flashcards

Volcanic Activity Flashcards

(73 cards)

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1
Q

What does a vent eruption lead to

A

Formation of a cone shaped mountain

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2
Q

What does a fissure eruption lead to

A

The formation of a wider and flatter plateau

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3
Q

What’s magma called at surface

A

Lava

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4
Q

Two ways magma rises through to surface

A

Vent and fissure

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5
Q

Why do volcanoes erupts

A
  1. As Magma rises, gases in the magma expand making bubbles, creating pressure that forces the magma upwards
  2. Magma meets groundwater near surface of volcano and becomes like a pressure cooker
  3. Volcanic mountain bulges and expanding gases push through the cracks in the volcano
  4. When the bubbles reach the surface the pressure is released, the bubbles expand and the volcanoes erupt
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6
Q

Life cycle of volcanoes

3 types

A

Active
Dormant
Extinct

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7
Q

Active volcanoes explain and example

A

Continuously errors or erupted recently and likely to erupt in the near future

Eg Mt.Etna Italy
Mt. Loa Hawaii

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8
Q

Dormant volcano explain and example

A

Has not erupted in a very long time (+100 years) but may do so again.

Eg. Yellowstone National Park volcano dormant for 640,000 years
Mt. St. Helens, USA, dormant for 128 years before its devastating eruption

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9
Q

Extinct volcano explain and example

A

Not erupted in recorded history

Eg Slemish in co.antrim has not erupted in 15million years as Ireland moved away from plate boundary

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10
Q

Volcanic material deposited when volcano erupts

A

Lava
Pyroclasts
Poisonous gases
Water vapour

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11
Q

2 types of lava are

A

Acidic lava and basic lava

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12
Q

Differences between acid and basic lava

A
  • Acidic has a higher Silica content than basic
  • Acidic is sticky and viscous, thicker and doesn’t flow as easily as basic due to more trapped gases than basic
  • acidic is very explosive where as basic is non explosive and has more gentle eruptions
  • acidic is less hot at 800c where as basic is hotter at 1200c
  • acidic volcanoes form at convergent plate boundaries and subduction zones. Basic form at divergent and hotspots
  • when acidic lava cools it forms steep sided volcanoes where as when basic volcanoes cool they form gently sloping volcano landforms
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13
Q

What are pyroclast

A

Hot ash, lava and rock fragments thrown out by a volcano

Sometimes referred to as volcano bombs

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14
Q

How is pumice created

A

Lava mixes with air causing it to fill with bubbles

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15
Q

What are pyroclastic flows

A

Boiling clouds of ash and rock which travel at speeds of up to 600km/hr

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16
Q

Poisonous gases emitted by volcanoes

A

Carbon monoxide, carbon dioxide, sulphur dioxide and chlorine

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17
Q

Which volcanoes release water vapour

A

Those formed at subduction zones involving an oceanic plate

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18
Q

What occurs when water vapour from volcanoes rises

A

Torrential downpours

This mixing with lava, ash and rock can cause Lahars (landslides)
Even worse when snow topped volcano

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19
Q

List the positive impacts of volcanic activity

A 
Geothermal energy 
Tourism
Fertile soil
New land
Valuable materials
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20
Q

Discuss geothermal energy as a positive effect of volcanic activity

A

Eg Iceland
Magma that rises close to surface heats ricks and groundwater absorbs this heat and becomes hot. Water becomes super heated . Wells are drilled into the rock and the hot water is pumped out of the ground.

Water reaches the surface and turns into steam which drives turbines generating electricity. The still hoy water is piped to nearby areas to neat homes and businesses

When water is cooled it helps vegetation growth

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21
Q

Discuss tourism as a positive effect of volcanic activity

A

Volcanoes are important tourist attractions

They generate revenue and employment for the local area

Eg Iceland has roughly 60000 visitors each year to see the volcanic landscape and springs eg blue lagoon hot pools and spas

Eg Pompeii

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22
Q

Discuss Fertile soils as a positive effect of volcanic activity

A

Ash and cinders rich in nutrients act as a natural fertiliser

Vegetation in an area that has suffered from volcanic activity grows back relatively quickly

After being eroded and weathered, lava turns into fertile soil

eg in Hawaii, pineapple and sugar plantations are located in volcanic soils

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23
Q

Discuss new land as a positive effect of volcanic activity

A

Iceland was created about 16-18 million years ago by cooled basalt rock which cooled at the Atlantic ridge

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24
Q

Discuss valuable materials as a positive effect of volcanic activity

A

Can be found in volcanic or igneous rocks

Eg gold, silver, diamonds, copper, lead and iron

The presence of these materials rises to mining

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25
Ways volcanologist predict volcanic eruptions
``` Seismic activity Ground deformation Gas emissions History of volcanic eruptions Increase in sulphur and carbon levels in soils on or close to volcanic slopes Increase in temperature of ground water Fumes, smoke and ash and steam seen ```
26
How can seismic activity be a way of predicting volcanic eruptions
Earthquakes occur as magma and gases force their way upwards through cracks in the crust. As magma rises, rocks vibrate Seismometers are places within 20km of the vent as earthquakes can be small and difficult to detect.
27
How can volcanoes be detected by ground deformations
Swelling of a volcano signals that magma is rising within it. Measurement of swelling can be done by: EDMS (electric distance measurement) devices any horizontal movement Tiltmeters detect change in slope level GPS satellites monitor the earths surface and record changes in volcanic shape Satellite Radar records images of volcanoes
28
Function of EDMS
Electronic distance measurement devices measure any horizontal movement of a volcano
29
Function of a tiltmeter
Detect change in slope
30
GPS satellites function
Monitor the earths surface and record any changes in volcanic shape
31
Function of satellite radar
Records images of volcanoes
32
Why are gas emissions a sign of a volcanic eruption
Before an eruption, gas emissions increase by more than 5-10 times their normal levels. As magma nears the surface, gases escape more easily Eg. 500 tonnes of sulphur dioxide per day was released from Mount Pinatubo. This increased by 5000 tonnes per day before the volcano erupted
33
How can the history of volcanic eruptions be a way to predict future eruptions
Can show a pattern of eruptions Eg Mount Katia in Iceland erupts every 80 years on average, it last erupted in 1918 and has been showing signs of unrest since 1999. It’s being closely monitored since the neighbouring Eyjafallajökull volcano erupted
34
Example of a volcano at a divergent boundary
Mount Helka, Iceland
35
Example of a volcano at a convergent boundary
Eg Mount Saint helens , Washington State
36
Example of a volcano at a hotspot
Moana Loa, Hawaii
37
Volcanic structures formed form an extrusive volcano (quick cooling)
Central vent eruptions cause volcanic cones Hotspots cause volcanic cones Fissures- cause lava plateau and mid ocean ridges
38
What are intrusive/ plutonic volcanic structures
``` Batholiths Sills Dykes Laccoliths Lopolith ```
39
Types of volcanic cones
Cinder volcanoes Composite volcanoes/ stratovolcanoes Dome volcanoes/ lava domes Shield volcanoes
40
Discuss cinder volcanoes
Smallest type Steep sides Wider crater made of cinder and dried deposits that fall back after eruptions Explosive eruptions Only erupt once as eruptions destroy their structure Usually surrounding composite volcanoes as shield
41
Discuss composite or stratovolcanoes Our normal volcano Give an example
``` Form at convergent boundaries in violent eruptions Acid slow flowing lava Alternate layers of lava and pyroclasts Steep sided Secondary vents Eg Mount Etna, Mount Vesuvius ```
42
Discuss dome volcanoes and lava domes
Lava domes sometimes are found in crater of composite volcanoes due to building up after eruptions or when thick lava gets pushed out of the vent and hardens They act as a “lid” on the volcano Extremely violent eruptions as lid flings off Example, Mount St Helens
43
Discuss a shield volcano
Form at hotspots (and sometimes divergent boundaries) in non violent eruptions Basic fast flowing lava Eruptions build up layers of lava and pyroclasts Gentle slope Wide base Example; Mount Loa, Hawaii
44
How is a Caldera formed
When large quantities of molten magma are blown out of volcano the magma chamber can be come partially emptied and may not be able to support the cone above it resulting in a collapse. A larger depression called a Caldera forms Eg in Yellowstone National Park
45
Where do fissure eruptions take place and what forms there
Where plates pull apart eg floor of atlantic ocean resulting in the underwater mountain range, the mid ocean ridge Lava flows out of a crack or fissure in earths crust allowing lava to flow over large areas eg Antrim Derry plateau
46
How are plutonic structures classified
By shape
47
5 plutonic structures are
``` Batholiths Laccoliths Lopoliths Sills Dykes ```
48
What are batholiths
Magma chamber Deeply buried in earths crust, made of course granite Exposed hen crust above is denudated eg Leinster Batholiths, Wicklow Mountains, Dublin.
49
What are laccoliths
Dome like structures of hard igneous rock that bulged upwards against overlying rock strata
50
What are lopoliths
Hard intrusive rock that sag downwards due to weight of magma
51
What are sills | How are they formed
Horizontal sheets of igneous rock that run parallel to the under and overlying rock strata Form when magma forces its way into bedding plane sod sedimentary rocks and is cooled and solidified
52
What are dykes
Vertical sheets of volcanic rock that cooled and solidified in vertical cracks in rock
53
Opposite of dykes
Sills
54
Opposite of laccoliths
Lopoliths
55
Where is Mount pinatubo located
The Destructive (convergent) plate boundary of the Philippine and Eurasian plate
56
Build up of eruption of Mount pinatubo
Seismic tremors and steam emission over the years Earthquakes and steam, sulphur dioxide emissions increase in lead up Small bulges for, Ash and lava began or escape
57
Discuss Eruptions In Mount pinatubo 1991 eruption
``` Lasted a week Violent, vicious lava, gas Pyroclastic flows in all directions Typhoon - Lahar Batholith emptied - Caldera ```
58
Consequences of Mount pinatubos 1991 eruption
Effected air traffic Global temperatures dropped by about 0.5 degrees as energy was absorbed from the sun Gases destroyed a hole in the ozone layer 800 deaths from collapsing roofs and diseases 2 million people’s properties damages Farming production was ceased Now a major tourist attraction
59
What’s an extrusive volcanic Landform
One that is made outside of the surface
60
What’s an intrusive volcanic landform
One that’s made inside the surface
61
Irish intrusive volcanic feature
Leinster batholiths, Dublin mountains, Wicklow mountains and Blackstairs mountains
62
Extrusive volcanic feature in Ireland
The Antrim Derry Plateau
63
Why are batholiths surrounded by metamorphic rock
The intense heat of the molten magma in the batholith changes the sedimentary rock to metamorphic rock such as quartz and schist due to the heat and pressure of the magma
64
Magma cools below ground to form
Granite
65
Rock batholiths change sedimentary into
Metamorphic eg quartz and schist
66
Identify two characteristics of a dome volcano
Steep slope as lava cools close to vent | Acidic lava which doesn’t flow fast. It has a high silica content and is very explosive
67
Identify two characteristics of a shield volcano
Gentle sloping side and wide base | Basic lava which is runny travels long distances, less explosive
68
Negative effects of volcanic eruption
Loss of life : lava, pyroclastic flow eg Mt Vesuvius, 10,000 deaths Lahar : eg Nevada del Ruz, $1 billion worth of damage in armario Poisonous gases: eg Cameroon, 1700 died due to carobom dioxide released from lake in volcano crater Disruption to air travel: ejafalljokull 2010 caused 20 countries to stop airtravel
69
Size of Antrim Derry plateau
4000km squared
70
When did Antrim Derry plateau form
When Eurasian and North American plate were divergent 65 million years ago Basic eruption
71
How many hexagons in giants causeway
60,000
72
Why are the rock hexagon in giants causeway
Cooled in a river valley
73
How did Leinster batholiths form
``` Molten magma forced its way up (less dense than surrounding rock) Bulge in rock above Sedimentary changed to metamorphic Overlying sedimentary weathered But still has schist capstone ```

Leaving Cert Geography - (23 decks)

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