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Leaving Cert Geography - > Volcanic Activity > Flashcards

Volcanic Activity Flashcards

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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
Q

Ways volcanologist predict volcanic eruptions

A 
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
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26
Q

How can seismic activity be a way of predicting volcanic eruptions

A

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.

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27
Q

How can volcanoes be detected by ground deformations

A

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

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28
Q

Function of EDMS

A

Electronic distance measurement devices measure any horizontal movement of a volcano

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29
Q

Function of a tiltmeter

A

Detect change in slope

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30
Q

GPS satellites function

A

Monitor the earths surface and record any changes in volcanic shape

31
Q

Function of satellite radar

A

Records images of volcanoes

32
Q

Why are gas emissions a sign of a volcanic eruption

A

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
Q

How can the history of volcanic eruptions be a way to predict future eruptions

A

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
Q

Example of a volcano at a divergent boundary

A

Mount Helka, Iceland

35
Q

Example of a volcano at a convergent boundary

A

Eg Mount Saint helens , Washington State

36
Q

Example of a volcano at a hotspot

A

Moana Loa, Hawaii

37
Q

Volcanic structures formed form an extrusive volcano (quick cooling)

A

Central vent eruptions cause volcanic cones
Hotspots cause volcanic cones
Fissures- cause lava plateau and mid ocean ridges

38
Q

What are intrusive/ plutonic volcanic structures

A 
Batholiths
Sills
Dykes
Laccoliths 
Lopolith
39
Q

Types of volcanic cones

A

Cinder volcanoes
Composite volcanoes/ stratovolcanoes
Dome volcanoes/ lava domes
Shield volcanoes

40
Q

Discuss cinder volcanoes

A

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
Q

Discuss composite or stratovolcanoes

Our normal volcano
Give an example

A 
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
Q

Discuss dome volcanoes and lava domes

A

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
Q

Discuss a shield volcano

A

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
Q

How is a Caldera formed

A

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
Q

Where do fissure eruptions take place and what forms there

A

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
Q

How are plutonic structures classified

A

By shape

47
Q

5 plutonic structures are

A 
Batholiths
Laccoliths
Lopoliths
Sills
Dykes
48
Q

What are batholiths

A

Magma chamber Deeply buried in earths crust, made of course granite

Exposed hen crust above is denudated eg Leinster Batholiths, Wicklow Mountains, Dublin.

49
Q

What are laccoliths

A

Dome like structures of hard igneous rock that bulged upwards against overlying rock strata

50
Q

What are lopoliths

A

Hard intrusive rock that sag downwards due to weight of magma

51
Q

What are sills

How are they formed

A

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
Q

What are dykes

A

Vertical sheets of volcanic rock that cooled and solidified in vertical cracks in rock

53
Q

Opposite of dykes

A

Sills

54
Q

Opposite of laccoliths

A

Lopoliths

55
Q

Where is Mount pinatubo located

A

The Destructive (convergent) plate boundary of the Philippine and Eurasian plate

56
Q

Build up of eruption of Mount pinatubo

A

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
Q

Discuss Eruptions In Mount pinatubo 1991 eruption

A 
Lasted a week
Violent, vicious lava, gas
Pyroclastic flows in all directions
Typhoon - Lahar
Batholith emptied - Caldera
58
Q

Consequences of Mount pinatubos 1991 eruption

A

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
Q

What’s an extrusive volcanic Landform

A

One that is made outside of the surface

60
Q

What’s an intrusive volcanic landform

A

One that’s made inside the surface

61
Q

Irish intrusive volcanic feature

A

Leinster batholiths, Dublin mountains, Wicklow mountains and Blackstairs mountains

62
Q

Extrusive volcanic feature in Ireland

A

The Antrim Derry Plateau

63
Q

Why are batholiths surrounded by metamorphic rock

A

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
Q

Magma cools below ground to form

A

Granite

65
Q

Rock batholiths change sedimentary into

A

Metamorphic eg quartz and schist

66
Q

Identify two characteristics of a dome volcano

A

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
Q

Identify two characteristics of a shield volcano

A

Gentle sloping side and wide base

Basic lava which is runny travels long distances, less explosive

68
Q

Negative effects of volcanic eruption

A

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
Q

Size of Antrim Derry plateau

A

4000km squared

70
Q

When did Antrim Derry plateau form

A

When Eurasian and North American plate were divergent 65 million years ago
Basic eruption

71
Q

How many hexagons in giants causeway

A

60,000

72
Q

Why are the rock hexagon in giants causeway

A

Cooled in a river valley

73
Q

How did Leinster batholiths form

A 
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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