Volcanic Activity- Hazards

  • Created by: Evie :)
  • Created on: 08-10-21 17:55
What factors make a volcano dangerous?
Unpredictable/heat, fire/ death/ inhaling fumes/ speed of lava/low education levels/ Location/ respiratory problems/ frequency of eruptions
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What is viscosity?
Thickness of a liquid
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What is low viscosity in magma?
runny/ thin magma
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What is high viscosity in magma?
Sticky, gloopy, thick magma
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What type of viscosity makes a volcano more explosive?
High viscosity/ andesitic or rhyolitic magmas
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What are LAHARS?
volcanic ash mixing with water and flowing considerable distances downhill
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What causes LAHARS to form?
melting snow and ice caused by eruptions, mixing with ash/ ejecting water from a volcanic crater lake mixing with ash/ pyro flows can generate these as hot rock debris erodes, mixes with and melts snow/ice
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What is Lava?
Molten rock(magma) flowing to the surface of a volcano.
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What are pyroclastic flows?
Formed from a mixture of hot ash and tephra which can flow at speeds of over 700km/h down a mountain.
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how are pyroclastic flows formed?
when the column of lava, ash and gases expelled from a volcano during an eruption looses its upward momentum and falls back to the ground/ Also can form when a lava dome or lava flow becomes too steep and collapses
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What is tephra?
the solid material erupted by a volcano into the air
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Where is there a large population of of active volcanoes
Pacific plate- destructive margin// African plate- constructive (Namibia)// North American plate (destructive/ conservative) - Alaska
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Where are volcanic hotspots ( frequent eruptions)?
Hawaii (pacific plate) Canary islands (African plate)
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How are the islands of Hawaii formed?
The pacific plate slid over a plume of magma, puncturing the earths crust/ The upwelling of molten rock 'hot spot' creates volcanoes that eject lava and then the lava cools, hardens and creates new land (creation of islands)
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lava characteristics at constructive margins
comes from deep within the mantle of the earth/ basaltic lava/ associated with mid oceanic ridges and along rift valleys// (lava found at hotspots)
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Characteristics of lava produced at destructive margins
comes from melting of subducted oceanic crust/ acid or andesitic lava/ associated with Pacific Ring of fire
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Basaltic lava facts
Least explosive lava/ Low viscosity(runny)/ Volcano types- Icelandic, Hawaiian/ plate margin associated- Constructive, Hot spots/ Basalt gabbro rocks formed when cooled
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Andesitic lava facts
Moderately explosive/ Intermediate viscosity/ associated volcano- Vesuvian/ associated plate margin- Destructive/ Andesite diorite rocks formed when cooled
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Rhyolitic lava facts
most explosive lava/ high viscosity (gloopy)/ associated volcano- Plinian/ associated plate margin- destructive/ rhyolitic granite rocks formed when cooled
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What does morphology mean ( classification of volcanoes)?
the shape of a volcano, during classification
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Fissure volcano characteristics?
less defined morphology/ Thin layers/ basaltic lava( low viscosity)/ example- Holuhraun Iceland
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Shield volcano characteristics?
less defined morphology/ basaltic lava ( low viscosity)/ No layers, completely fluid/ example- Mauna Loa- Hawaii
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Dome Volcano characteristics?
Defined morphology (steep)/ rhyolitic and andesitic lava ( more explosive)- high viscosity/ alternating layers, thick mainly/ example- Puy de Dome, France
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Stratovolcano(composite) characteristics?
Defined morphology/ thick layers/ rhyolitic lava ( high viscosity) / examples- Kraktoa, Indonesia/ Vesuvius, Italy
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What are the 7 classifications of volcanoes, according to the type of eruptions they create?
Icelandic/ Hawaiian/ Vesuvian/ Vulcanian/ Plinian/ Strombolian/ Pelean
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Icelandic volcano characteristics
basaltic lava (low viscosity) / lava flows gently from fissure vents/ less violent/ can be constant
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Hawaiian volcano characteristics
basaltic lava(low viscosity)/ lava flows gently through central vents/ less violent/ can be constant
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Strombolian volcano characteristics
Thick basaltic lava/ frequent and explosive eruptions of tephra and steam/ regular but not constant
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Vulcanian volcano characteristics
Thich basalric, andesitic or rhyolitic lava/ violent eruptions/ less frequent/
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vesuvian volcano characteristics
thick basaltic, andesitic or rhyolitic lava/ very violent ash eruptions following periods of inactivity/ ash sent high into the sky/ less frequent
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Pelean volcano characteristics
Andesitic or rhyolitic lava/ very violent eruptions of pyroclastic flows/ less frequent
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Plinian volcano characteristics
rhyolitic lava/ very violent eruptions of gas, ash and pumice/ if rainfall occurs simultaneously, can cause lahars/ less frequent
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when was the last volcanic eruption of magnitude 7?
Tambora, Indonesia 1815
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when was the last volcanic eruption of magnitude 8?
Indonesia 73,000 years ago
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Facts about the Mt. St Helens eruption
Magnitude 5 eruption/ Mountain collapsed into 2 landslide blocks/ Landslide depressurised the magma and reduced ground water/ Lava forced its way up the mountain causing rocks to slide, leading to earthquakes
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How can volcanic frequency be determined?
Deposits created by the volcano and calculating the dates of these. E.g, thickness of rocks
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What are active volcanoes?
Volcanoes which have erupted within living record (70-80 years)
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What are dormant volcanoes?
Volcanoes which last erupted within historical records (800+ years ago)
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what are extinct volcanoes?
Volcanoes which haven't erupted for 10,000 years
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what is volcanic eruption prediction, relating to frequency?
this is determined by calculating how regularly a volcano erupts and the average time between eruptions/ e.g, Vesuvius is expected to erupt on a 70 year cycle, due to past records but this hasn't been accurate/ erupted 7 times in 1700s but hasn't in 77 ye
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how can seismometers record siesmic activity, to predict volcanic eruptions?
microquakes can indicate rising magma, cracking and fracturing rocks
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how can tiltometres and laser distance measurements be used to precict volcanic eruptions?
bulging of the ground can suggest rising magma/ slope angles can be measured very accurately using electronic devices
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How can monitoring groundwater predict volcanic eruptions?
Rising magma will heat groundwater and increase its acidity as sulphur dissolves into it
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how can remote cameras be used to predict volcanic activity?
They can identify small eruptions, ash escaping and landslides/ also thermal cameras can be used to detect increased temperatures
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primary impacts of volcanic eruptions
Landslides/ gas emissions/ lava flows/ pyroclastic flows/ Tephra sent into the atmosphere
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secondary impacts of volcanic eruptions
Death/ Injuries/ earthquakes/ lahars moving down rivers/ water contamination/ tsunamis if lava enters the sea/ greenhouse gases can increase temperatures/ ash can cover the sun- global cooling/ acid rain is caused by lava entering the sea or due to landsl
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human responses to volcanic eruptions
hazard managment plan/ protection methods= build lava trenches( concrete barriers to divert lava), evacuation plans with medical facilities on standby, warning systems( texts or media), land use planning laws to keep pop densities lower
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EYJ volcano Iceland characteristics
Located on the mid atlantic ridge ( prone to eruptions)/ Volcano covered by ice caps feeding glaciers/ Strato volcano
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Nature of the volcanic eruptions in EYJ, Iceland
seismic activity detected and showed that magma was pouring from underneath the crust into the magma chamber
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what is the benioff zone
the area where friction is created between colliding tectonic plates, resulting in intermediate and deep earthquakes/ situated between a desructive plate boundary and oceanic crust is subducted here then melted
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Other cards in this set

Card 2


What is viscosity?


Thickness of a liquid

Card 3


What is low viscosity in magma?


Preview of the front of card 3

Card 4


What is high viscosity in magma?


Preview of the front of card 4

Card 5


What type of viscosity makes a volcano more explosive?


Preview of the front of card 5
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