Chapter 7: Volcanoes Study Guide
Name __________________________________ Period ____
Section 7-1 Volcanoes and Plate Tectonics (pages 200-203)
1.
A volcano is a weak spot in the crust where ________________ _________________ comes to the surface.
2.
A molten mixture of rock-forming substances, gases and water from the mantle is referred to as _________.
3.
When magma reaches the surface, it is called _____________________.
4.
The ________________ ______ _______________ is a major volcanic belt formed by a long chain of volcanoes that rim the Pacific Plate.
5. Most volcanoes form along which 2 plate boundaries?_____________________ and __________________
6. Volcanoes form along the mid-ocean ridge when ______________________________________________
______________________________________________________________________________________
7. True or False? Volcanoes can form along diverging plate boundaries on land. ________________________
8. True or False? Many volcanoes form near converging plate boundaries where oceanic crust subducts. ____
9. Volcanoes at boundaries where 2 oceanic plates collide create a string of islands called an ______________
__________________.
10. Give 3 examples of island arcs. _____________________________________________________________
11. Circle the letter of the types of plates that collided to form the Andes Mountains on the west coast of South America.
a. two oceanic plates b. a continental plate and an oceanic plate c. a continental plate and an island plate d. two continental plates.
12. A ______________ ________________ is an area where magma from deep within the mantle melts through the crust like a blow torch.
13. The Hawaiian Islands formed as the ______________________ plate drifted over a hot spot.
14. True or False? Hot spots only form under oceanic crust. __________________________________
Section 7-2 Properties of Magma (pages 205-208)
15. A substance the cannot be broken down into other substances is called a(n) _______________________.
16. True or false? When frozen water melts, it is undergoing a physical change. _________________________
17-18. Circle the statements that indicate a chemical property. a. Water boils at 100°C under normal conditions. c. an iron chair will develop rust if oxygen combines with b. When paper is burned, it forms ashes.
the iron. d. A basketball is larger than a baseball.
19. The greater the viscosity, the _______________________ a liquid flows. The _______________________ the viscosity, the more easily a liquid flows.
20-21. Circle the letter of each liquid that has a relatively low viscosity. a. milk b. molasses c. ketchup d. orange juice e. milkshake
22. The viscosity of magma is determined by the amount of _________________ and its __________________.
23-24. Circle the letter that is true about silica. a. It is formed from oxygen (O) and nitrogen (N). b. It makes magma thicker. c. It is rarely found in the crust. d. It produces light-colored lava.
25. The rock ______________ forms from light-colored lava. Low-silica magma forms rocks like___________.
26. The higher the temperature, the ___________________________ the viscosity.
27. Hot, fast-moving lava is called ________________________________.
28. Cool, slow-moving lava is called _____________________________.

Viscosity of Magma Temperature Silica Content
High
31.
29.
Higher
30.
32.
Section 7-3 Volcanic Eruptions (pages 209-216)
33. True or False? Magma usually forms in the asthenosphere (part of lithosphere)._______________________
34. True of False? Liquid magma rises until it reaches the surface or until it becomes trapped beneath layers of rock.
________________________________________________________
35. During a volcanic eruption, the force of the expanding gases pushes magma from the ___________________
_____________________ through the __________________ until it flows or explodes out of the _________________.
36-37. Circle the letters of the features that all volcanoes share . a.
pocket of magma b. cracks to the surface c. side vents d. crater
38. A ______________________ ____________________ is the area covered by lava as it pours out of a vent.
39. A ____________________________ forms at the top of a volcano around the central vent.
40. True or False? The pipe of a volcano is a horizontal crack in the crust. _____________________________
41. The 2 main factors that determine whether a volcanic eruption will be quiet or explosive are the magma’s
______________________ content and __________________________.
42. High- viscosity magma causes _________________________ eruptions.
43. Volcanic ____________ is made up of fine rocky particles as small as a speck of dust.
44. Pebbles sized particles are called _________________.
45. Particles ranging in size from the size of a baseball to the size of a car are called _____________________.
46. A ____________________________________ _________________ occurs when an explosive eruption hurls out a mixture of ash, cinders, bombs and a mixture of REALLY HOT & deadly gases (melts your skin).
47. True or False? The activity of a volcano may last from less than a decade to more than 10 million years. ___
48-50. Volcanoes are dangerous because their lava flows start ________________ and bury everything in their path. If it becomes wet from rain, volcanic ash becomes very heavy and causes _____________________ to collapse. Engines of cars and _____________________________ stall if the ash clogs the engine. Due to snow-capped volcanoes mixing with intense heat, ________________________ and ________________________ often occur. The ash and poisonous
_____________________ can be fatal to humans, animals and plants.
51. The three stages of a volcano: ______________________________ dead or very unlikely to erupt again
______________________________ erupting/showing signs of erupting
______________________________ sleeping, but expected to erupt again
52-53. Geologists who study volcanoes are called volcanologists. They use instruments like the
________________________ to monitor changes in elevation around volcanoes. They monitor any
________________________ that might be escaping from the volcano and also take temperature readings of underground ______________________. Small earthquakes are a sign that _________________ is moving under the surface.

Match each landform with its description.
_______ 54. shield volcano A. high, level area formed by repeated lava flows
_______ 55. cinder cone
_______ 56. batholith
B. mountain formed by lava flows alternating with explosive eruptions
C. forms when magma hardens in volcano’s pipe, (looks like giant tooth)
_______ 57. lava plateau
_______ 58. caldera
D. hole left by the collapse of a volcanic mountain
E. gently sloping mountain formed by repeated lava flows
_______ 59. volcanic neck F. cone-shaped mountain formed from ash, cinders and bombs
_______ 60. composite volcano G. mass of rock formed when magma cools inside crust and the layers of
rock surrounding it erode
61. When volcanic rock erodes and creates soil, it is very fertile due to the nutrients ______________________ and
________________________, both of which the enrich soil around volcanoes.
62. “Geo” means _____________________ and “therm” means heat, so geothermal means heat from the earth.
63. When groundwater is heated by a nearby body of magma or hot rock deep underground, it forms ______________
_________________. When hot water and steam become trapped and suddenly sprays above the surface it is called a
_________________________.
64. Geothermal energy is a tremendous renewable energy resource. The steam is piped into a ____________________, which spins a generator. California and New Zealand take advantage of this resource.