Volcanoes Flashcards
Where are volcanoes located?
Along tectonic boundaries and appear in long chains
Destructive and construction boundaries
Give an example of is chain of volcanoes
The Pacific ring of fire
What is the difference between lava and magma?
Lava is magma above the surface and magma is molten rock beneath the surface
What is viscosity?
It is the stickiness of the lava or its resistance to flow
The more silica the more resistant the lava is
What is a active volcano, a dormant volcano and an extinct volcano?
Active- erupted recently and frequently
Dormant- has erupted in the last 2000 years but not recently
Extinct- is unlikely to erupt ever again and is dead or extinct
What are the three types of lava?
Basaltic
Andesitic
Rhyolitic
What is a crater?
The basin shaped depression in the top of a volcano where material is ejected
What is a volcanic bomb?
Semi molten pieces of rock ejected from a volcanic vent
What is a secondary cone?
When there is great pressure inside a volcano and the vent or crater is blocked magma is forced to the surface by a different route
What is a magma chamber?
Where all the molten rock that comes out of the volcano is stored underground
What is the vent?
The Lin shaft that feeds magma from the magma chamber to the crater
What are the two types of volcanic landforms?
Extrusive and intrusive
What are extrusive landforms?
Molten rock reaching the surface can create these landforms; Shield Composite Fissure Acid dome Calderas
What are intrusive landforms?
Molten rock that are injected into the crust also create landforms that my not be seen in the surface
As magma cools slowly crystals are formed in rock
Batholiths are often done-shaped and exposed later due to erosion
What are the properties of rhyolitic lava?
Acid up to 75% SiO2
Very viscous up to 10^6 x that of basalt
Rarely forms flows, mainly domes and spires
Traps gas builds up pressure and explosively erupts so effects can be catastrophic
What are the priorities of andesitic lave?
Intermediate c. 65% SiO2
Considerably more viscous than basalt, up to 10^3 x basalt
Thicker so less extensive flows
What are the priories of basaltic lava?
C. 45% SiO2
- the least viscous of lava flows
- forms thin laterally extensive flows which are confined by topography
What are the 5 types of volcano?
Shield Acid dome Cinder cone Composite cone/ strato Caldera
What are the features of a shield volcano?
- constructive boundaries and hotspots
- low with gently sloping sides
- wide base
- eruptions aw frequent and non violent
- thin runny lava to travels far from vent, fast flowing with high silica content
What are the feature of acid dome and cinder cone volcanos?
- simplest form of volcano
- built from particles and blobs of lava
- has charged violent eruptions
- steep sided with a bowl shaped crater
- most are less than 1000 ft
- thick lave so can’t travel far
What are the features of a composite/ stratovolcano?
- destructive boundaries
- composed of alternating layers of ash and acid lava
- steep sided and symmetrical
- high with narrow base
- very explosive eruptions with pyroclastic flows
- explosive as lave cools in vent
- acid lava, very thick low silica content
What are fissure eruptions?
A fissure is a elongated fracture or crack at the surface from which lava erupts
- explosions typically dwindle to a central vent after a period of hours
- lava flow can flow back into the ground by luring into a crack or an open erupting fissure
What are the 7 types o eruptions?
- Icelandic
- Hawaiian
- Strombolian
- Vulcanian
- Vesuvian
- peléean
- Plinian
What are the properties of Icelandic eruptions?
Basaltic lava
Lava flows gently from fissures
What are the properties of Hawaiian eruptions?
Basaltic lava
Lava flows gently from central vent
What are the properties of Strombolian eruptions?
Thicker basaltic lava
Frequent explosive eruptions of tephra and steam
Occasional short lava flows
What are the properties of Vulcanian eruptions?
Thicker basaltic andesitic and rhyolitic lava
Less frequent but more violent eruptions of ash gas and tephra
What are the properties of a Vesuvian eruption?
Thicker basaltic andesitic and rhyolitic lava
Following long periods of inactivity very violent gas explosions blast ash high into the sky
What are the properties of Peléean eruptions?
Andesitic and rhyolitic lava
Very violent eruptions of nuées Ardentes
What are the properties of Pilnian eruptions?
Lava is rhyolitic
Exceptionally violent eruptions of gases ash and pumice
Torrential rainstorms cause devastating lahars
What are the features of a Caldera?
Cauldron like feature
Formed by the collapse of land following a volcanic eruption
Depression
What are the primary impacts of volcanic activity?
Ash Lava flows Nuees ardentes Pyroclastic flows Tephra Volcanic gases
Define ash, brief explanation and damages it could cause with a example
- ash is a mineral compound of organic substance formed from burning, pulverised lava
- formed during explosive volcanic activity
- causes air traffic, communication and technical errors can contaminate drinking resources
- Iceland
Define lava flows , brief explanation and damages it could cause with a example
Lava is produced during an eruption, least hazardous and travels distances depending on viscosity
- lava is formed as magma is heated by radioactive decay and pressure causes it to burst through the crust and when it surfaces lava is formed
- death, economic losses, damage infrastructure
- nyriagongo 2002
Define nuees ardentes , brief explanation and damages it could cause with a example
Fast moving could like mass of gas, hot ash and other ejected material
- formed when dome collapses during the pyroclastic flow, glowing cloud of fine Ash
- destroys vegetation, traffic and congestion death and injury
- Mt Pelée 1902
Define pyroclastic flows , brief explanation and damages it could cause with a example
Fast moving current of hot gas, ash and rock
- formed when the eruption Column collapses during an eruption and the column is ejected upwards
- destroys buildings, vegetation, kills wildlife and causes traffic death and injury
- example is Mt St Helens
Define tephra, brief explanation and damages it could cause with a example
Solid matter, such as ash, dust, and cinders, that is ejected into the air by an erupting volcano
- formed when a eruption occurs and pyroclastic material is ejected from the volcano
- endangers human life, transportation disruption, water and power supplies damaged, technical equipment ruined
- example is the Alaskan volcanoes
Define volcanic gases, brief explanation and damages it could cause with a example
Variety of substances given off by active volcanoes, such as sulphur dioxide & carbon dioxide from primordial and recycled constituents form mantle, groundwater and earths atmosphere and Assimilated constituents form the earths crust released duringj an eruption
- hazardous to people and essential water and food supplies, animals and vegetation
- Mt St Pinatabu in 1991
Define acid rain, brief explanation and damages it could cause with a example
Rainfall made so acidic by atmospheric pollution it causes environmental harm
- harmful gases like sulphur dioxide and CO2 released after eruption also water vapour which is ejected into the upper atmosphere
- destroys eco systems and agriculture, removes nutrients and minerals from the soils
- acid rain in nyriagongo 2002
Define climate change, brief explanation and damages it could cause with a example
A change in global and regional climate patterns, distribution of changing weather patterns
- When volcanoes erupt, they emit a mixture of gases and particles into the air. Some of them, such as ash and sulphur dioxide, have a cooling effect, because they reflect sunlight away from the earth. Others, such as CO2, cause warming by adding to the the greenhouse effect
- sea level rising, flood and storms, droughts
- active volcanoes around world
Define lahars, brief explanation and damages it could cause with a example
A lahar is a type of mudflow which is triggered as a direct result of a volcanic eruption
- Heavy rainfall saturates soil and during a eruption soil becomes lubricated and a lahar is triggered
- destroy homes, death, traffic disruption and loss of vegetation
- Mt St Helens 1995
Define landslides, brief explanation and damages it could cause with a example
A collapse of a mass of earth and rock after an eruption due to steep sides
- eruption sends vibrations and the downward force of gravity is stronger than the force holding up the particles
- human and animal life in danger, vegetation destroyed, transport held up
- Mt St Helen’s 1995
Define flooding, brief explanation and damages it could cause with a example
Volcanic flooding occurs as snow melt is fast and the soil becomes so saturated surface runoff occurs
- homes destroyed, migration, over saturation of the land and habitats destroyed
- Bangladesh flooding from Naples
Define tsunamis, brief explanation and damages it could cause with a example
A long high sea wave triggered by a submarine volcano
- volcano erupts underwater it sends out shock waves which can trigger a tsunami
- deaths, destruction, economy damaged especially sea ports
- Indian Ocean tsunami 2004
What is the explosiveness of a volcano measured by?
The volcano explosivity index (VEI)
What can be used to approximate the explosiveness of an eruption?
The degree to which airborne volcanic products have been fragmented (tephra)
The greater the explosivity the greater the…
Fragmentation of the tephra deposits
What is the scale of the VEI?
0-8
What are historical eruptions measured on?
- Volume of ejecta
- Height of the eruptive column
- Qualitative descriptions
- Style of past activity
- Height of spreading of the eruptive plume head
What characteristics does the VEI scale take into account?
Plume height
Volume
Classification (eruption type)
Example
What does 0-8 in the category plume heigh represent? (VEI)
<100->25km
What does the volume on the VEI measure at?
1000s m3 - 1000s km3
What does the classification range from on the VEI?
Hawaiian to ultra-plinian
On the VEI frequency table, what does 0, 4 and 8 stand for?
0- frequent
4- tens per decade
8- two per 100,000 years
How do we monitor seismic activity and what do micro quakes indicate?
Using seismometers and recited using a seismograph
Micro quakes indicate rising magma fracturing and cracking the overlying rocks
How is ground deformation monitored, and what does ground bulging indicate?
Is measured using tilt meters and laser-based electronic distance measurement
Is caused by rising magma, both slope angles and the increasing distance between set points can be measured accurately
How is iron rich magma monitored and what does changing magnetism indicate?
Upward movement of iron rich magma is measured using magnetometers
Changing magnetism within the volcano is a common geophysical indication of rising magma
How is rising ground water monitored and what does the rising magma indicate?
Riding ground water temperature and gas content is measured using a hydrological instrument
Rising magma will both heat groundwater and corrupt it with gases such as sulphur (increasing its acidity)
How are warning signs monitored and what do they indicate?
Warning signs such as small eruptions, emissions of gases, landslides and rock falls can be recorded in real time using remote sensing equipment
Solar-powered digital camera surveillance record physical changes, thermal imaging and gas sampling
Name 5 positive impacts of a volcanic eruption
- geothermal power, pollution free, alternate fuel to fossil fuels- Iceland and New Zealand
- fertile soils ideal for farming -Naples
- igneous rock contains minerals gold and copper in chile
- igneous rocks used for buildings Naples
- geysers and volcanoes are a tourist attraction and provide revenue for local economy - yellow stone national park
What are the two types of aid?
Technical- HIC’s supply high cost monitoring equipment
Financial- used aid during and after event
