Volcanoes g110 lecture prepared by Bob Hall revised 7/31/2000 Points to Be Covered on Volcanos Products of eruptions Lava properties vs composition Fissure eruptions Types of volcanoes Distribution of volcanoes World Famous Kilimanjaro Fujiyama Mt St Helens Mauna Loa Mt St Helens
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lecture prepared by Bob Hall
Products of eruptions
Lava properties vs composition
Types of volcanoes
Distribution of volcanoes
Mt St Helens
Mt St Helens
Range from mafic (e.g. basalt) to felsic, like all ign rx
Solids lofted into atm from others (called pyroclastics. Better than fireworks?
Rocks may form from fusing of pyroclastics can range from dense (tuff) to light (pumice)What do we expect in a volcanic eruption?
What gas is overwhelmingly the most abundant volcanic gas?
Water vapor. Over (95%)
Isn’t that how we got our oceans, streams, etc.
Our hydrosph, yes. And our atm
Oxygen, nitrogen, carbon dioxide, carbon monoxide, hydrogen sulfide (stinky), hydrogen chloride (??), sulfur dioxide (bad guy?), ammonia
Erupt basaltic lava.
Low viscosity, moves fast and far.
Where are these fissures?
The ocean floor in spreading centers.
Anywhere on land?
Yes, wherever rifting has occurred.
Check out the Colombia Plateau. Great thicknesses of basalt lava.
Buildup primarily from basalt flows.
Long, low-angle slopes.
Form of an inverted shield.
Almost entirely pyroclastics.
Short, steep slopes.
Slopes at steepest angle possible for size of pyroclastics.
Usually depression at top of cone.
Pyroclastics build up.
Lava flows extend laterally.
Alternating lava and pyroclastics.
Convergent plate boundaries
Circum-Pacific Ring of Fire
Divergent plate boundaries: oceanic ridges