Vulcanicity Content Flashcards
Name the potential hazards produced by volcanic eruptions
- Lava flows burn and bury crops
- Submarine/coastal eruptions can cause tsunami
- Ash falls ruin machinery and disrupt transport
- Ash can cause respiratory difficulties
- Lahars
- Flooding from lava and debris blocking rivers
- Pyroclastic flows
- Snow melt causing dangerous lahars
- Volcanic dust absorbs solar energy, lowering global temperatures
Name some potential benefits of volcanic eruptions
- Lava flows create new land
- Geothermal power
- Igneous rocks contain rare mineral deposits
- Volcanic sulphur is used in agricultural and pharmaceutical processes
- Igneous rocks make excellent building material e.g. Most of Aberdeen’s buildings are made from granite
- Extinct volcanoes make excellent defensive sights e.g. Edinburgh castle
- lava and ashes weather quickly into fertile soils
- Volcanoes can be great tourist attractions
What does vulcanicity refer to?
All volcanic activities related to magma being pushed into the crust
Where is volcanic activity mainly located?
Along plate margins in belts
What are the four types of boundary, process that can produce volcanoes? And give examples of these
- Spreading ridges- constructive plate margins- mid Atlantic ridge
- Subduction zones- destructive plate margins- Pacific ring of Fire
- Rift valleys- The Great African Rift Valley
- Hot spots e.g. Hawaii
How many active volcanoes are there in the world approximately?
1500
What differences are there in the lava at constructive and destructive plate margins?
Constructive- basaltic
Runny, less viscous, low in silica
Destructive- acidic (andesitic rhyolitic)
Slow flowing, viscous, high in silica
How do volcanic eruptions differ at constructive and destructive plate boundaries?
Constructive: little violence, gases easily escape
Destructive: potentially explosive, lava shatters into pieces
What are the differences in terms of material erupted at constructive and destructive margins?
Constructive: mainly lava
Destructive: lava, ash, dust
What are the differences in terms of the frequency of eruptions at constructive and destructive margins?
Constructive: regular and can be continuous
Destructive: from time to time, long dormant periods
What are the differences in terms of the form the volcano at constructive and destructive margins?
Constructive: lava plateau, shield volcano, lava only
Destructive: acid lava dome, composite cone, layers of ash and lava
Do extrusive landforms have finer or larger crystals in their resulting igneous rocks?
Finer- this is because they cool faster
Do rocks resulting from intrusive landforms have larger or finer crystals?
Larger crystals- this is because they cool slowly
Give an example of a fissure eruption
Heimay, Iceland 1973
What’s the name of the famous lava plateau in Northern Ireland on the edge of which the giants causeway is located?
The Antrim lava plateau
Where would you find fissure volcanoes?
Rifts and early constructive margins
Describe the eruptions of fissure volcanoes
Gentle and persistent
Give an example of a shield volcano
Maura loa, the largest volcano in the world
Do shield volcanoes usually have few or many vents?
Many
Where would you find shield volcanoes?
Hotspots and where oceanic meets oceanic crust
Describe the eruptions of shield volcanoes
Gentle and predictable
Give some examples of composite come volcanoes
- Mount Etna
- Mount Vesuvius
- Mount Fuji
Where would you find composite cone volcanoes?
Destructive margins
Describe the eruptions of composite cone volcanoes
explosive and unpredictable
Name a region where many acid/dome volcanoes would be found
Puy, in central France
Where are acid/dome volcanoes found?
On continental crust
What is the range a caldera volcano can be from and to?
1-50km
Name two examples of caldera volcanoes
Crater lake, USA and Krakatoa, Indonesia
What height do few ash and cinder cone volcanoes exceed?
1000 feet
Name an example of an ash and cinder cone volcano
Paracutin-Mexico it has slopes of 25-35 degrees
What are the type of magma and characteristics of an Icelandic eruption?
Magma: basaltic
Characteristics: lava flows gently from fissures
What are the type of magma and characteristics of a Hawaiin eruption?
Magma: basaltic
Characteristics: lava flows gently from a central vent
What are the type of magma and characteristics of a Strombolian?
Magma: basaltic (thicker)
Characteristics: frequent, explosive eruptions of tephra steam. Occasional, short lava flows
What are the type of magma and characteristics of a Vulcanian eruption?
Magma: basaltic (thicker), andesitic, rhyolitic
Characteristics: less frequent, but more violent eruptions of gases, ash and tephra (including lapilli)
What are the type of magma and characteristics of a vesuvian eruption?
Magma: basaltic (thicker), andesitic, rhyolitic
Characteristics: long periods of inactivity, then very violent gas explosions blast ash high into the sky
What are the type of magma and characteristics of a peléean eruption?
Magma: andesitic, rhyolitic
Characteristics: very violent eruptions of nuèe ardents
What are the type of magma and characteristics of a plinian eruption?
Magma: rhyolitic
Characteristics: exceptionally violent eruptions of gases, ash and pumice. Torrential rainstorms cause devastating lahars
How does a geyser come to erupt?
- Water is heated through contact with hot rocks
- Pressure builds until an eruption takes place
- The vent then re-fills and the cycle is repeated
Why are geysers relatively short lived? (In geological terms)
Ground water conditions change and vents collapse
Name an example of a geyser
Old faithful- Yellowstone national park
Stokkur- Iceland
Do fumaroles cease to exist when a volcano becomes extinct?
No, they can persist for thousands of years after a volcano has become extinct
If the gas produced by a fumarole is sulphur, what are the fumaroles then called?
Solfataras
Name two examples of batholiths
Dartmoor
The Isle of Arran
How big can batholiths be?
Hundreds of kilometres in diameter
The area around a batholith can be altered to form a what?
Give an example of this
A metamorphic aureole an example of this is limestone being transformed into marble
What is a high concentration of dykes in an area known as?
A dyke swarm
Name a location where a dyke swarm can be found
Kildonan on the Isle of Arran
Give an example of a sill
The Great Whin Sill
What are both sills and dykes made from?
Dolerite
What are the primary effects of a volcanic eruption?
- Tephra
- Pyroclastic flows
- Lava flows
- Volcanic gases
What are the secondary effects of volcanic eruptions?
- Lahars
- Flooding
- Tsunamis
- Volcanic landslides
- Climatic change
How does prediction help in volcano hazard management?
It often involves hazard mapping analysing seismic shockwaves patterns, sampling gas and lava emissions and remote sensing of changes in topography, heat and gas emissions by satellite
Give an example where prediction of a volcanic eruption saved lives
Popocatepetl, Mexico 2000- seismic shockwaves alerted volcanologists to the threat of an eruption, which occurred 48 hours after the local population was evacuated
How does protection help manage earthquake hazards?
Warnings are issued and instructions given on how to react before, during and after an eruption. In the longer term, hazard mapping and land-use planning may be used to avoid development in areas at risk.
