Volcanoes Notes
I. Volcano: An ________________ in the earth's crust through which __________ flows out as ________
•
Magma that comes to _______________ originates from the ‘zone of ___________’ in the mantle
(zone of weakness is at the base of the plates)
•
The plates put _______________ on a zone and forces magma ______ through cracks and openings
•
Most volcanoes are near ___________ boundaries, where ________________ occur.
•
Exception – _________________ islands, in the Pacific Ocean ‘Ring of Fire’
•
_______ spots form when hot magma from below earth’s crust _________ to the surface
II. Structure of Volcanoes
•
Crater: is the opening at the ________ of the volcano
•
Lava settles back down into the crust and a solid _______or
_________ forms in the crater
•
___________ is the channel through which the magma travels
•
Dormant: volcano __________ or ____________.
Ex: Mt. St. Helen’s was dormant for 100 years
•
Extinct: Volcano that has_______ erupted within historic
times. (________ was here and recorded)
Ex: Mt. Lassen in California until 1913
•
Active: Volcano that has ____________ & smokes _______
•
Caldera: A very large ______________ located at
the top of the volcano
•
Laccolith: mass of hardened magma that is ________
shaped (magma moves _____________ layers causing
bulge)
•
Batholith: large mass of igneous rock
(______________ magma) below earth’s surface
•
Dikes: magma fills and hardens in __________ cracks
•
Sill: a structure of hardened magma between
________________ layers of rock
•
Stock: ___________ mass of hardened magma
below the earth’s surface
III. Three Main Types of Volcanoes
•
Classified by shape of ___________ (how lava ______________ out)
•
Cone: ________ of material that collects around the _____________________
•
1. Shield Cone: Lava runs out ___________ from the opening and forms
gently sloping sides, almost __________, quiet eruptions
•
2. Cinder Cone: An ______________ type of eruption and is built up by
layers of ash and cinders. (________________ sloped sides than sheild)
•
3. Composite Cone: ______ explosive and quiet eruptions. Alternating
layers
of _____________ & lava flows, (like cake & icing)
IV. Volcanic Eruptions
•
A. Eruptions depend on…..
–
1. If the vent is _______________ or ___________
–
2. The ____________________ of the vent. (long vents release gases
at _________ speeds)
•
B. Four Basic kinds of Eruptions
–
–
1. Quiet eruption with ____________ lava flow
•
Magma is thin
•
Magma contains little gas
•
Thin lava flows out in a steady stream
2. Quiet eruption with thick lava flow
•
Magma contains little gas
•
Thick lava forms huge dome
3. Active Eruption
•
–
Thin magma with _________ amounts of _____
–
Gas escapes – causes hot __________ to shoot _______
4. Explosive eruption
•
–
Magma __________ with large amounts of _______
–
Magma ___________ before leaving the vent (blocked)
–
Trapped gas under ________ _________________
–
Sudden release - __________________
V. Types of Materials
•
A. Lava
–
Pahoe hoe – hot, ______, and fast flowing.
•
–
–
_______________ surface
Aa – cooler and thicker
•
________, block – like surface
•
____________, hurts to walk on (‘ah – ah’)
___________ lava: forms on ____________ floor
•
B. Gases
–
Water vapor – ______________ water in magma
–
_________ monoxide, ___________ dioxide, &
hydrogen sulfide
–
_________ gasses ______________and cannot escape,
so pressure builds up and volcano _________________
•
C. Pieces of rock (pyroclastic material)
–
Volcanic dust – ______________, 2 mm or less
–
________ – fragments, ________ sized
–
Cinders – sent out by eruptions, several _____ across
–
Bombs – __ ___________ across
–
_________________ – weighing several ________
VI. Volcanoes and Man
–
________________ out civilizations (landscapes)
–
Predicting eruptions

_________ earthquake activity around the ________________

__________ inside the crater may steam and ____________
Problems
Benefits
1. Can cause climate _______ (blocking sun with ash)
1. Ashes spread & creates ______ soil
2. ___________ property & people
2. Hot Springs in Iceland for _________
3. Colorful _________ for several years
4. _____________ use for polishing