large areas when they erupt.Review Questions
- Rank the four types of volcanoes in order from smallest to largest in diameter.
- What factor is most important in determining the type of volcano formed in a given
area? - Which type of volcano is most common?
- Why is it that pahoehoe and a’a lava are more frequent in shield volcanoes than in
composite volcanoes? - Why do you think that cinder cones are short-lived?
- If supervolcanoes are so big, why do you think it took so long for scientists to discover
them?
Vocabulary
caldera Circular-shaped geographic features formed from a massive eruption of an ancient
volcano, and the subsequent collapse of the volcano back into the ground.
cinder cone A smaller volcano that grows rapidly but only erupts over a short period
of the time. Cinder cones are composed of small rock fragments piled on top of one
another. They rarely are more than 300 m in height.
composite volcano A volcano with a broad base, steep sides, and often a crater at the
top. The volcano is composed of alternating layers of ash and lava flows. Also called
a stratovolcano.
strata Layers of rock that are similar in composition to one another.
supervolcano Amassivevolcaniceruptionthatisrarebutincrediblypowerful. Thousands
of cubic kilometers of matter can be ejected, and the dust and ash from their eruption
can cool the world’s climate for years.
Points to Consider
- Composite volcanoes and volcanic cones usually have craters on the top. Why are the
craters not always circular, but sometimes “U” or horseshoe-shaped? - A shield volcano is relatively flat, and a composite volcano is relatively steep because
of the type of magma that creates them. What process might create a volcano that is
more steep than a shield volcano but not as steep as a composite volcano?