EAS 201: Lecture 11
January 30, 2019
• Slide information borrowed from Karlis Muehlenbachs January 30,
• Image taken from Karlis Muehlenbachs slides January 30, 2019.
o Can be classified by location – Subaerial (under air),
Submarine, or Subglacial.
o Classified by shape – Shield Volcano, Tephra Cone, or
o Other volcanic landforms include – Calderas & Fissure
• Shield Volcanoes: broad, roughly dome-shaped, basaltic.
o Biggest by size, but w/ surface slopes of only 5-10 degrees.
• Tephra Cones & Stratovolcanoes:
o Rhyolitic & andesitic eruptions tend to eject a lot of
pyroclasts = steep-sided volcanoes (tephra – rock
fragments/particles ejected by eruption).
o The bigger stratovolcanoes are steep cone-shaped
mountains made of layers of lava & tephra.
• Volcanic Disasters:
o Hazards form stratovolcano eruptions occur as:
▪ Hot, fast moving nuee ardentes (fast moving cloud of hot gases) & lateral
blasts → aka “pyroclastic flow”.
▪ Tephra & hot poisonous gases bury/suffocate.
▪ Tephra + rain = lahar (deadly mudflow).
▪ Violent undersea eruptions cause tsunamis.
▪ Tephra destroys agricultural land as well as cities.
o Classification by activity
▪ Active – erupted in recent history.
▪ Dormant – no historic eruptions, not badly eroded.
▪ Extinct – no historic eruptions and is badly eroded.
▪ Seismic activity, steam forming/temp changes.
▪ Bulging, tilting or uplift.
▪ Gas emissions around a volcano.
o Beneath every volcano, complex of chambers & channels that magma moves
through as it goes towards the surface.
o The chambers are filled w/ igneous rock.