volcanoes and volcanic activity Flashcards
volcanic erruptions
- an event during which lava and/or pyroclastic debris expelled from a volcanic vent
-there is verylittle we can do to control volcanic eruptions. we dont fully understand the process and we need to know the process to be able to mitagate - iceland has good ways to deal with erruptions because they have increased volcanic activity
magma
molten rock
lava
magma th at reaches the earth’s surface (will eventually cool)
krakatoa
- sound heard 3000 miles away
- 40m high tsunami killed over 36000 people
- high ash coud produced
- one of the biggest agents to impact global temperature
- global temp reduced 0.5C for 10 years after krakatoa
what is the affect of ash clouds
- decreases albedo
- light reflects off ash clouds thereby decreasing global temperature
Anak Krakatau (indonesia)
- active from july 2018- may 2019
- lies in crater of krakatoa
- major collapse in 2018 causes a tsunami which killed over 400, injured over 7000, and displaced over 40000
- volcano lost more than two thirds of its height and volume in one week
- pheratic, explosive erruption
steam explosions
- island arcs: seawater seeps into rock and comes into contact with magma
- steam produced and blows volcano (pheratic eruption which are very disrupive; ground/seamwater connected to and acting with volcanic chambers)
Jokulhlaups in Iceland
- a type of glacial lake outburst flood (subglacial)
- often associated with subglacial outburst floods caused by volcanic eruptions
- eruption melts water and builds up pressure
- can deposit/ erode sedimens and change proglacial landscape dramatically
- ex Eyjafjallajokull eruption in iceland created over 140 events; glacial activity and volcanic together; 10 million cubic meteres of water, tephra and sediment
underwater volcano in tonga on jan15
- 5 people killed
- largest eruption since 1991 mount pinatubo
- ash cloud
- shockwaves felt across the globe
- magma was forced upward at high highspeed
- high speed contect with cold sea water causes “fuel-cooland interaction” building up lots of pressure
- magma torn apart exposing fragments to more sea water
- chain reaction and massive chemical explosion
- particles forced up to hypersonic speed
- people on tonga faced drinking water crisis
- caused a massive oil spill in peru
why s it important to understand how volcanoes work?
- many people are killed or displaced
- we cant prevent volcanoes but we can be prepared for them to preent loss of life and individuals wellbeing
- to understand the nature of earth’s interior
- magma comes from the matles
- there is kimberlite and diamonds
what is geothermal energy
- using heat from the earth for electricity
- commonin New Zealand, Iceland, BC, and Chile
- often near volcanoes
pyroclastic debris
- lava and rock fragments ejected in a volcanic eruption
- theres different scales: lapilli (small amount of lava and rock fragments) and lava bomb (large amounts of lava, larger than 2.5 inches)
volcano
- hill or mountain produced by volcanism
- volcano doesnt have to be active to be considered
- the name is based on how it was formed
vent
opening through which eruption takes place
crater
depression over the vent
caldera
depression >1km
- same as crater but just larger
where do we find volcanoes
- divergent plate boudnaries ex. mid ocean ridges, Iceland
- convergent plat boundaries ex. pacific ring of fire, krakatoa, cascade volcanoes (mt. st. helens)
- hot spots: not associtaed with plate boundaries. ex. hawaii, yellowstone. related to mantle plumes. plume is stationary, plate moves. chain of volcanic islands produced
plumes
narrow colums of hot rock
how many types of lava are there
- 2 types
- affects style of erutpion and type of volcano produced
- silica content of magma is critical
types: - silica rich (felsic) lavas
- silica-poor(mafic) lava
- intermediate lavas
silica-rich (felsic) lava
- very viscous, flow slowly
- gases cannot escape easily
- violent erruptions, explosive
- ex. rhyolite
- iceland
silica-poor (mafic) lava
-low viscosity, flow easily
- gases escape easily
- quite eruptions, lava flows
- ex. basalt
- hawaii and iceland
intermediate lavas
- ex. andesite
types of volcanoes
- 3 main types
- shield
- cinder (pyroclastic) cone
- composite (stratovolcano)
hot spots
- a region deep within the Earth’s mantle from which heat risen is not associted with plate boundaries
shield volcanoes
- broad, sloping cones (slopes between 2 and 10 degress)
- low viscosity lava flows (silica poor (mafic))
- non-violent eruptions
- ie. hawiian islands (mauna loa)
- basaltic lavas flow easily
- two types: pahoehoe and A’a
- spatter cones (shield volcanoes with smaller vents): formed on shile volcanoes when gas is trapped in cooling lava, usually less than 10 m in height
- composition: basalt, laers of solidified lava flows
- very large
pahoehoe
- ropey
- hot lava
- in silica poor lavas
- liquidy
A’a
- sharp, jagged (cooler)
(cinder) pyroclastic cones
- made of loose pyroclastic debris
- steep slopes, small
- felsic or intermediate lavas
- formed when gas escapes
- 50-350m in height
- violent eruptions
- ex. sunset crater, arizona
- steep slopes, 33 degrees
- smallest of the three types
- composition: pyroclastic fragments of any compositions. basalt is most common
Composite volcanoes (stravolcanoes)
- alternating lava flows and pydroclastic debris
- intermediate steepness
- form over long period
- can be very large
- mostly associted with intermediate lavas (andesite) and violent eruptions
- ex. mt. st. helens (usa), mt etna(italy), mt vesuvius (italy)
- associted wih lots of hazards
- slopes less than 33 degrees
- considerably larger than cinder cones
- composition: layers of pyroclastic fragments and lava flows. mostly andesite
what kinds of hazards are produced by volcanoes
lava flows (nothing we can do to stop lava)
- destructive to proterty, roads, etc
- ex of volcanic hazars. 2018 kilauea eruption, hawaii
pydroclastic debris (volcannic bombs, ash which can contaminate water supply)
- ex. mt st helens which was the most destructive explosion in continental usa in recent human history
pyroclastic flows (nuees ardente; mixture of hot gases and volcanic debris, travels at >100km/hr, extermely dangerous, mixture of toxic and hot gases coming at you, lots of human deaths due to this, cant stop it, NOT seen in shield volcanoes)
- ex. mont unzen (japan) in 1991
- ex. st.piere, martinique,1902, mt pelee, killed 28000, only 2 survivors
debris flows (lahars): mudflows (pyroclastic material debris and water), flow along river valleys; less destructive than pyroclastic flows
- ex. nevado del ruiz, colombia: lahars reachers speeds of 50km/hr, over 23000 dead
toxic gases: water vapour, co2, co, hydrogen sulphide, sulpher dioxide, heavier than air, move along topographic depressions
- ex. lake nyos, cameroon, 1700 people killed by c02
natural hazard
what nature does
natural disaster
- humancentric
- is a disater if it impacts society/people/infrastructure
types of volcanic explosions
How are different types of volcanoes, volcanic activity and volcanic rocks related to plate tectonic setting?
