announcements
• Someone reminded me yesterday that we’re in the 6th week of classes already
• I need to give you another exam, so that we can drop one…so…
• WEDNESDAY MARCH 7 (so I can be sure it get it back before spring break). Review Monday 5th, 5 PM, here.
• Turn in your Pinatubo video worksheet please• READ: chapter 3, p. 68 - 86 (don’t panic, lots
of pictures)
Today/Friday (there is an outline on the website)
• What are the different materials that come out of a volcano? What are the compositions involved?
• What are different kinds of volcanoes?
• Where do they erupt?
• What makes a volcano erupt the way it does?
What are the different materials that come out of a volcano?
Terms to memorize…• Pyroclast: anything exploded out of the vent
– ash (very small fragments)– lapilli (small rocks) and bombs (large rocks)– pumice and cinder– ash flow, also called pyroclastic flow– ash-flow tuff, also called pyroclastic-flow
deposit
pumice fall
ash-flowtuff
cinder cone
What are the different materials that come out of a volcano?
Terms to memorize…• Lava: magma that is effused (that flows) out
of the vent, no explosion– crystal size depends on cooling speed
lava flow
a few thousand years
a few thousand seconds
What are the different materials that come out of a volcano?
Terms to memorize…• Lahar: Indonesian word for volcanic mudflow:
ash + water, + whatever else is around; needs a slope
Candi Morangan,Indonesia, where lahar met a Hindu temple in ~860 AD
Mount St. Helens, 1980
What are the different materials that come out of a volcano?
• Gases– dominantly H2O and CO2, plus CO, SO2,
H2S + HF
nice-looking lake, yes?
What are the compositions of volcanoes: what are magmas
made of?More terms to memorize• Basalt• Andesite• Dacite• Rhyolite
What do these words mean and what do they tell us about volcanoes?
What are the compositions of volcanoes: what are magmas
made of?• Basalt• Andesite• Dacite• Rhyolite
You need a note-taker, a leader, an assistant, and a time-keeper/reporter for this
Fruit salad
• 20% blueberries
• 20% strawberries
• 20% kiwis
• 20% bananas
• 20% apples
Basalt
• highest-temperature magma: all magma starts life as basalt
• high-temperature minerals are really easy to form, but hard to preserve
• if you take all the blueberries out of a fruit salad, what you have left over will have 0% blueberries and 25% strawberries, 25% kiwis, 25% bananas, and 25% apples
Andesite
• moderate-temperature magma• moderate-temperature minerals form
from the high-temperature ones as the magma cools
• take the blueberries and the strawberries out of the fruit salad, what you have now is 33% kiwis, 33% bananas, and 33% apples
Dacite
• cooler-yet-temperature magma• cooler-temperature minerals form from
the moderate-temperature ones as the magma cools
• take the blueberries and the strawberries and the kiwi slices out of the fruit salad, what you have now is rich in 50% bananas and 50% apples
Rhyolite: the 50% bananas and 50% apples left in the fruit salad
• you started with 20% of 5 different kinds of fruit
• coolest-temperature magma
• coolest-temperature minerals form from the cooler-temperature ones as the magma cools
• chains of silica
