- A
- B
- C
Listen to a lecture in a geology class, take detailed notes while listening.
crater – a bowl-shaped depression
conical – cone-shaped
geological – pertaining to the Earth
magma chamber – a space inside a volcano that contains liquid rock when full
typical – usual
Fill in the following diagram.
Definition
1.
Types
Causes
A 2.
3.
B 4.
5.
Now answer the questions using your notes.
Calderas
What characteristics describe each volcano? Place a check mark in the correct box.
Summarize the text using your notes and diagram.
- 1: A big crater at the top of a volcano.
- 2: Explosive.
- 3: Eruption.
- 4: Non-explosive.
- 5: Collapse of the magma chamber.
Listen again:
M1: Today I'd like to talk about a geological feature called a volcanic caldera. If you think about a typical volcano, what does it look like to you?
W: Well, um, it's probably shaped like a cone.
M1: Indeed, many volcanoes are conical – not all though. Are there, uh, any other, um, features of a typical volcano?
M2: Don't they usually have a big crater at the top?
M1: Many volcanoes do – that crater is what we mean by the caldera. There are two types. One type is an explosive caldera. That type of caldera is caused when a volcano erupts in a violent explosion. After the explosion, a hole remains. This is exactly what happened when Mt. St. Helens erupted in 1980. The entire top and part of the side of the mountain are now gone. In place, you can see the volcano's caldera. Future eruptions will continue to shape its caldera, maybe even fill it in partially. Do you have any ideas what might cause the other type—a non-explosive caldera?
W: Hmm… the volcano doesn't explode?
M1: Nice try. A non-explosive caldera is caused, not by an eruption, but when an underground magma chamber in the volcano empties and collapses. That's what happened to Hawaii's Kilauea, which has never had such violent and explosive eruptions like that of Mt. St. Helens. You can visit this active volcano and see its caldera today.
