Volcanoes Flashcards
What is a shield Volcano?
Large with broad, gentle slopes with gentle eruptions
What color is the lava from shield volcanoes?
Dark colored
What is a stratovolcano (composite)?
Small but tall with violent, sticky eruptions
What color is the lava from stratovolcanoes?
Light colored
Shield volcanoes have more
Volume
Hawaiian
Gentle outpourings of runny lava
Rift eruptions
Gentle outpourings of runny lava from a linear rift rather than a crater
Lava Fountain
Vigorous eruption with runny lava. Powered by gas
Cinder Cone
Piles of volcanic “cinders” (small blobs of cooled lava from the fountain)
Strombolian
Mildly explosive fountaining. Thicker, more viscous
Vulcanian
Moderately explosive. Ash plume <5 km
Pelean and Plinian
Strongly explosive. High and large ash clouds and eruption volumes
What is more powerful, Pelean or Plinian?
Plinian
What is a phreatic eruption?
Lava interacts with water or ice
Surtseyan
Lava interacts with seawater
What is an explosive eruption
Cooler, more viscous lavas reach the surface
Eyjafjallajokull
Explosive eruption powered by the melting and boiling of glacial ice
Ubehebe crater
Explosion caused by interaction between lava and groundwater
Caldera
Larger than a crater, formed by the collapse of the surface into the lava chamber after it has been emptied by a large eruption
Gentle eruptions
Shield, dry, mafic
Where do gentle eruptions happen
Divergent boundaries
Violent eruptions
Strato, wet, felsic
Where do violent eruptions happen
Convergent boundaries
Which is underground
Magma
Which isn’t underground
Lava
How do pyroclastic flows form
Collapse of ash cloud
Up to what speeds are pyroclastic flows travelling?
700 km/hr
Up to what temperatures are pyroclastic flows
1000C
What volcanic hazard destroyed Pompeii and Saint-Pierre?
Pyroclastic flow
What is a Lahar
Fast, high volume mudslides triggered by the melting of ice or breaking crater lakes
Why is a lava flow dangerous
Not because it’s fast, but because they are generally unstoppable
Basaltic (Gentle) lava speed
60 km/hr in channels and tubes, <6km/hr at flow fronts
Nyiragongo lava speed + how much it killed
100 km/hr, killed 70
What are toxic gasses
Gasses often confined to crater and ash cloud
Lake Nyos
Massive CO2 release in 1986 that killed 1700 people and 6000 heads of cattle
Ash Falls
Buries stuff and shreds lungs
Earthquakes and landslides
Caused by the movement of lava; Can be a sign of eruptions or other hazards
Mitigation 1: Monitoring
Look for
-Earthquake activity
-Heatflow
-Ground movement and shape
-Gas emissions
Mitigation 2: Preparation
Successful evacuations vs. false alarms; long-term predictions in danger assessment maps
What factors determine wether the volcano will erupts effusively vs. explosively?
Magma composition and water content
What is an effusive eruption
Steadily flows from the volcano to the ground
Are phreatic eruptions common at mid-ocean ridges?
No. Mid-ocean ridges are thousands of feet underwater and there is too much pressure for steam explosions when the lava touches the water
What kind of magma forms shield volcanoes
Basaltic Magma
What kind of magma forms stratovolcanoes
Andesitic/rhyolitic magma
