Volcanoes Flashcards
Types of volcanoes
small monogenetic landforms and large stratovolcanoes, shield volcanoes and calderas
What are calderas?
Large explosive eruption from underlying magma chamber
How are calderas formed
The withdrawal of the underlying magma chamber causes the overlying ground to collapse underneath
What are monogenetic volcanoes and examples
small and short -term subaerial volcanoes ved by small volume of magma.
Examples include lava domes and cinder cones
What are strata volcanoes
They are a type of composite volcano, built of a plethora of layers of lava and explosive volcanic material ( years)
Example of calderas
Oregon Crater Lake
How are lava domes formed
The slow extrusion of highly-viscous silicic lava.
How are cinder cones formed
built from particles and blobs of congealed lava ejected from a single vent
Types of lava domes Petrographically
Crystal poor obsidian and crystal rich rhyolitic, basaltic andesite
Types of lava domes
Petrographically spreaking, there are crystal -poor, obsidian and crystal rich rhyolitic - basaltic andesite
What types of volcanic eruptions can occur
effusive and explosive
What factors are dependent on the type of volcanic eruption
physical properties of the erupting magma whether its viscosity or volitility
what are the four levels of Magmatic explosive eruptions
Hawaiian, Strombolian , Vulcaina , Plinian
Least explosive
Hawaiian
Most explosive
Plinian
Properties of Hawaiian
little bursts of lava flows, outwards, gentle and effusive
Properties of Strombolian
Mild blast lasting around >1hr
Properties of Vulcanian
Driven by gas locked within the volcano
Properties of Plinian
Most powerful explosions, sustained, and continuous lasting for days
What are Phreatomagmatic
Explosive eruptions with groundwater interaction
generating an increased explosivity
What is the VEI stand for?
Volcanic Explosivity Index measuring the magnitude to frequency relationship
Different type of parameters
volume of tephra
Cloud column and height in km
qualitative descriptions
eruption types
duration
CAVW max explosivity
Tropospheric interjection
What is the distribution of active volcanoes
Linked to the plate tectonics ( and its few annomalies)
Majority are along the plate margin
Plate margin examples
Divergent , convergent
Hotspots
located in the middle of plates, hotspots of magma are gentle eruption which due to the movement of plates, form chains of islands
Divergent example
Iceland
Convergent example
cascade
Intraplate Volcanism Oceanic Example
Hawaii
Intraplate Volcanism Continental
Yellowstone
Variability
volcanoes display a tremendous diversity in mag intensity , style and duration of eruption over days - decades
Uncertainty
Variability in how an eruption might unfold
Tephra fall
As the material produced from an explotion reached up towards the surface, pressure increases causing fragmentation from the surface region to froth and through the volcanuc plume, material explodes up and outwards
1991 Pinatubo eruption
Ash accumilated depths of 10-15cm at airfield of 40 km South west of the P
How many Volcanic Ash Advisory Centers are there?
9
What is the prupose of the Vocalnic Ash Advisory Centers?
They advice the aviation industry of the location and movement of ash clouds
What is Cristobalite?
A type of polymorph silica mineral forming in domes and pr prismatic crystals.
How and where do Cristobalite form
Within vesicles and cracks, by vapour phase crystalisation
What is an example of an area which this process occured
Chaiten, Chile ( 2008-2010)
What is the pyroclastic density current
This is a fludized mixture of solid to semi -solid fragments and hot expanding gases
How does PDC travel
Pyroclastic density current flows fast , hot and unpredictably down the flank of a volcanic edifice, causing the column and dome to collapse
Speed of PDC
> 100km/hour
Where are there examples of PDC in the world?
Soufriere Hills Volcano
Montserrat
Why are they turbulent?
mixture of hot material and cold air
Why are they valley confined
The dense basal flow consistsing of large block of ash
Top?
Gas rich , finer grains of ash entrains the cold air wth the hot material
What is the PDC flow
Dense movement made of large blovks confined in the hill
What is a PDC surge
turbulent and dilute as it travels uphill
Example of pyroclstic flow
Mount Pelee 1902
- peak of volcano explosion at the peak of the volcano, both pyroclastic flow and surges occured
28,00 residents
3 survivors
Lava flows are dependent on…
chemical composition ( 700-1200 degrees Celsius)
land formation ( angle/slope of land )
What is pahoehoe lava
A fluid flowing form of lava with a ropey surface
A ‘ā lava
Rough and jaggered form of lava
What was the DRC 2002 event
Within Nyiragongo and the City of Goma , the volcano produced extreme volume of lava
Travel speed - 100 km
How far did the lava flows reach?
15 km periodically as it inundated Goma
Type of gases emmited from volcanoes?
CO2 carbon dioxide
SO2 sodium dioxide
H2S hydrogen sulfide
H2SO4 sulfuric acid
HCL hydrochloric acid
HF hydrogen Floride
CO2
Trees killed by high carbon dioxide conc. at
Mammoth Mtn., CA
its denser than air - significant amounts accumilate on lowlands and valleys
Example of how it affects Cameroom
Killing livestock from the release of CO2 from the Cameroom lakes, Nyos
Example of how Sulfur affects Ijen, Indonesia
Global effects of gases
Sulfate Areosoles can form from the interaction between sulfur, co2 and atmosphere
can absorb IR by aerosols
backscatter from aerosols
ash particles in the stratosphere
What was the 1815 Tambora event
The summer of 1815, Tambora eruption occured but the global effects were only felt in the following year
Global cooling, most prevalent in Europe causing sig number of deaths
Lahars
Type of volcanic mudflow whereby a glacial flood outburst during raining seasons.
What are the different types?
Syn-eruptive (Kelut )
Post-eruptive (Pinatubo) e.g pyroclastic flow - raining season – reactivate pyroclastic flow forming mudflows.
What is the Nevado del ruiz event
1985
Eruption melted the ice cap
Ice mixed with volcanic material
- Engulfing of Armero >50 km downstream
-killing 23,000
Who identified this hazard
Colombian and Italian volcanologists
When have these events last ocuured
1595,1845
Volcanic landslide and lateral blast example
Mount st Helens
What happnened on 18th May 1980
A build up of lava increaing the pressure collapse, landslide, explsion of volcano
What was the harbour wave Tsunami in Japan
A volcanic eruption occuing underneath the sea, by the ocean
Hitting land reaches up to 40 meters high
Subsequent tsunami in Hilo Hawaii on 1 April 1946
