Volcanic Activity Flashcards
What does a vent eruption lead to
Formation of a cone shaped mountain
What does a fissure eruption lead to
The formation of a wider and flatter plateau
What’s magma called at surface
Lava
Two ways magma rises through to surface
Vent and fissure
Why do volcanoes erupts
- As Magma rises, gases in the magma expand making bubbles, creating pressure that forces the magma upwards
- Magma meets groundwater near surface of volcano and becomes like a pressure cooker
- Volcanic mountain bulges and expanding gases push through the cracks in the volcano
- When the bubbles reach the surface the pressure is released, the bubbles expand and the volcanoes erupt
Life cycle of volcanoes
3 types
Active
Dormant
Extinct
Active volcanoes explain and example
Continuously errors or erupted recently and likely to erupt in the near future
Eg Mt.Etna Italy
Mt. Loa Hawaii
Dormant volcano explain and example
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
Extinct volcano explain and example
Not erupted in recorded history
Eg Slemish in co.antrim has not erupted in 15million years as Ireland moved away from plate boundary
Volcanic material deposited when volcano erupts
Lava
Pyroclasts
Poisonous gases
Water vapour
2 types of lava are
Acidic lava and basic lava
Differences between acid and basic lava
- 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
What are pyroclast
Hot ash, lava and rock fragments thrown out by a volcano
Sometimes referred to as volcano bombs
How is pumice created
Lava mixes with air causing it to fill with bubbles
What are pyroclastic flows
Boiling clouds of ash and rock which travel at speeds of up to 600km/hr
Poisonous gases emitted by volcanoes
Carbon monoxide, carbon dioxide, sulphur dioxide and chlorine
Which volcanoes release water vapour
Those formed at subduction zones involving an oceanic plate
What occurs when water vapour from volcanoes rises
Torrential downpours
This mixing with lava, ash and rock can cause Lahars (landslides)
Even worse when snow topped volcano
List the positive impacts of volcanic activity
Geothermal energy Tourism Fertile soil New land Valuable materials
Discuss geothermal energy as a positive effect of volcanic activity
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
Discuss tourism as a positive effect of volcanic activity
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
Discuss Fertile soils as a positive effect of volcanic activity
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
Discuss new land as a positive effect of volcanic activity
Iceland was created about 16-18 million years ago by cooled basalt rock which cooled at the Atlantic ridge
Discuss valuable materials as a positive effect of volcanic activity
Can be found in volcanic or igneous rocks
Eg gold, silver, diamonds, copper, lead and iron
The presence of these materials rises to mining
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
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.
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
Function of EDMS
Electronic distance measurement devices measure any horizontal movement of a volcano
Function of a tiltmeter
Detect change in slope
GPS satellites function
Monitor the earths surface and record any changes in volcanic shape
Function of satellite radar
Records images of volcanoes
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
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
Example of a volcano at a divergent boundary
Mount Helka, Iceland
Example of a volcano at a convergent boundary
Eg Mount Saint helens , Washington State
Example of a volcano at a hotspot
Moana Loa, Hawaii
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
What are intrusive/ plutonic volcanic structures
Batholiths Sills Dykes Laccoliths Lopolith
Types of volcanic cones
Cinder volcanoes
Composite volcanoes/ stratovolcanoes
Dome volcanoes/ lava domes
Shield volcanoes
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
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
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
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
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
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
How are plutonic structures classified
By shape
5 plutonic structures are
Batholiths Laccoliths Lopoliths Sills Dykes
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.
What are laccoliths
Dome like structures of hard igneous rock that bulged upwards against overlying rock strata
What are lopoliths
Hard intrusive rock that sag downwards due to weight of magma
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
What are dykes
Vertical sheets of volcanic rock that cooled and solidified in vertical cracks in rock
Opposite of dykes
Sills
Opposite of laccoliths
Lopoliths
Where is Mount pinatubo located
The Destructive (convergent) plate boundary of the Philippine and Eurasian plate
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
Discuss Eruptions In Mount pinatubo 1991 eruption
Lasted a week Violent, vicious lava, gas Pyroclastic flows in all directions Typhoon - Lahar Batholith emptied - Caldera
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
What’s an extrusive volcanic Landform
One that is made outside of the surface
What’s an intrusive volcanic landform
One that’s made inside the surface
Irish intrusive volcanic feature
Leinster batholiths, Dublin mountains, Wicklow mountains and Blackstairs mountains
Extrusive volcanic feature in Ireland
The Antrim Derry Plateau
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
Magma cools below ground to form
Granite
Rock batholiths change sedimentary into
Metamorphic eg quartz and schist
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
Identify two characteristics of a shield volcano
Gentle sloping side and wide base
Basic lava which is runny travels long distances, less explosive
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
Size of Antrim Derry plateau
4000km squared
When did Antrim Derry plateau form
When Eurasian and North American plate were divergent 65 million years ago
Basic eruption
How many hexagons in giants causeway
60,000
Why are the rock hexagon in giants causeway
Cooled in a river valley
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
