Lesson 6: Volcanoes and Volcanic Eruptions Flashcards
A lava flows whose surface is broken into rough angular fragments is
a’a (ah-ah)
Tephra comes in three sizes; ___ is the smallest
ash
_______ are avalanches of hot ash, rock, volcanic glass fragments, and gas that move rapidly down the sides of the volcano during eruption.
Pyroclastic flows
The most abundant volcanic gas is ____.
Water vabor
A _____ is a Volcanic mudflow/debris flow
lahar
_____ is the most common risk to humans from lava flows.
Property damage
Which of the following is NOT a common cause of pyroclastic flows?
a. Boiling over from eruptive vent
b. Collapse of eruption column
c. Collapse of lava domes or flows
d. Megathrust earthquakes
d. Megathrust earthquakes
T/F: Lahars are only triggered by volcanic eruptions.
False
_____ eruptions are typically associated with shield volcanoes.
effusive
A ______ is a solid rock fragment greater than 64mm in diameter that was ejected from a volcano during an explosive eruption.
Block/bomb
Compare explosive and effusive eruptions.
Explosive: high viscosity
Effusive: low viscosity
What are the controlling factors of explosive eruptions
intermediate and felsic
higher viscosity
Usually violent vent eruptions
What are the controlling factors of effusive eruptions? (2)
Low viscosity
Fluid, gentle flowing magma
Compare fissure eruptions and vent eruptions
Fissure:
- common where the crust is undergoing extension and
where magma is relatively fluid (low viscosity)
- Are the dominant style of eruption
- Convergent and divergent plate boundaries
- pillow lavas
Vent:
- occur where lava is extruded at a central vent.
- Low viscosity
- Low volatile content
Explain Mafic lava eruptions’ characterization. (3)
Less viscous
Flow easily
Occurs mostly on the ocean floor
Ropy lava
Blocky lava
Sheild volcanoes
Cinder Cones