1. Ch. 9 Study Guide Answers
2011

2. A vent or fissure in the Earth’s surface through which magma and gases are expelled is called
A Volcano

3. What would you expect to see during a non-explosive eruption?
Huge lava flows.

4. Molten rock deep underground often gathers in a
Magma Chamber

5. Which type of lava flows most like dripping wax?
Pahoehoe

6. Lava that is very runny probably
has a low silica content

7. If the water content of magma is high,
an explosive eruption is more likely

8. When you talk about the viscosity of lava, you are talking about
how the lava flows (thickness).

9. Most active volcanoes form
(80%) where tectonic plates collide

10. Cool, stiff lava that forms in jumbled heaps of sharp chunks near the vent is called
Blocky Lava

11. Which type of pyroclastic material gets its name from a word that means “little stones”?
Lapilli.

12. The pyroclastic material that can reach the upper atmosphere and circle the Earth for years is
Volcanic Ash.

13. Pyroclastic material forms when
magma explodes from a volcano and hardens in the air.

14. Describe a possible climate change caused by a volcanic eruption?
Volcanic Ash high in the atmosphere could block sunlight, causing (regions of earths) temperatures to drop.

15. Where are volcanoes most likely to form?
Along plate boundaries

16. Large blobs of magma that harden in the air are called
Volcanic Bombs.

17. A large depression that forms when the magma chamber partially empties is a
Caldera.

18. The three main types of volcanoes are
Shield Volcano, Cinder Cone Volcano, and Composite Volcano.

19. The depression created when the roof of a magma chamber collapses is called a
Caldera

20. Rock begins to melt when (what happens)
temperature on the rock increases and pressure decreases

21. Most active volcanoes form
where tectonic plates collide

22. When an oceanic plate collides with a continental plate, the oceanic plate is usually sub-ducted because
the oceanic plate is denser and thinner than the continental crust.

23. A cinder cone volcano
has steep slopes

24. The volcanoes of Hawaii and other places far from tectonic plate boundaries are known as
Hot Spots

25. Which category of volcano is most likely to erupt in the near future?
An active volcano

26. An active volcano
is currently erupting or show signs of erupting. In the near future.

27. What would you expect to see during a non-explosive eruption?
Calm lava flows

28. Pillow lava is
formed when lava erupts under water

29. Lava with a high viscosity
is thick like pudding

30. What would you expect after an explosive eruption?
Darkened Skies.

31. A shield volcano
has gently sloping sides

32. A combination of explosive and non-explosive eruptions will create a
composite volcano