Directed Reading. Section: Volcanoes and Plate Tectonics

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1 Skills Worksheet Directed Reading Section: Volcanoes and Plate Tectonics 1. Some volcanic eruptions can be more powerful than a(n) a. hand grenade. b. earthquake. c. geyser. d. atomic bomb. 2. The cause of many volcanic eruptions is the movement of a. Earth s mesosphere. b. Earth s inner core. c. Earth s tectonic plates. d. Earth s oceans. 3. The movement of tectonic plates is driven by Earth s a. mantle. b. internal heat. c. internal forces. d. internal pressure. 4. Scientists can learn more about volcanic eruptions by studying a. temperatures within Earth. b. temperatures in Earth s atmosphere. c. external Earth temperatures. d. the movements of migrating animals. 5. Combined temperature and pressure in the lower part of Earth s mantle keeps rocks a. at their melting point. b. below their melting point. c. from reaching their melting point. d. above their melting point. FORMATION OF MAGMA 6. Despite high temperature, most of the mantle remains solid because of the a. large amount of ice above the mantle. b. space between the rock. c. large amount of pressure from the surrounding rock. d. lack of pressure from the surrounding rock. Holt Earth Science 7 Volcanoes

2 7. Sometimes Earth s solid mantle and crust melt to form a. magma. b. mesosphere. c. petroleum. d. mineral elements. 8. Which of the following is NOT a way magma can form? a. The temperature of rock rises above the melting point of the minerals the rock is composed of. b. Excess pressure is removed from rock that is above its melting point. c. Addition of fluids, such as water, increase the melting point of some minerals in the rock. d. Addition of fluids, such as water, may decrease the melting point of some minerals in the rock. VOLCANISM 9. Magma rises upward through the crust because a. the magma is less dense than surrounding rock. b. magma is more dense than surrounding rock. c. magma is the same density as the surrounding rock. d. the surrounding rock is porous. 10. As hot bodies of magma rise toward the surface and melt surrounding rock, a. they become smaller. b. they become larger. c. their size remains the same. d. they disperse. 11. As magma rises, and is forced into cracks in the surrounding rock, a. large blocks of rock break off and melt. b. large blocks of rock hold magma inside. c. large rocks are broken down. d. magma disperses. 12. Lava flows from an opening in Earth s surface called a a. depression. b. geyser. c. vent. d. blowhole. Holt Earth Science 8 Volcanoes

3 In the space provided, write the letter of the definition that best matches the term or phrase. 13. volcanism 14. lava 15. volcano a. a vent or fissure in Earth s surface through which magma and gases are expelled b. any activity that includes the movement of magma toward or onto Earth s surface c. magma that flows onto Earth s surface; the rock that forms when lava cools and solidifies MAJOR VOLCANIC ZONES 16. Volcanoes erupt on Earth s surface a. mostly in random locations. b. in all mountainous areas. c. only along the Pacific coast. d. mostly near tectonic plate boundaries. 17. A major zone of active volcanoes encircling the Pacific Ocean is called a. the Major Pacific Earthquake Zone. b. the Pacific Ring of Volcanoes. c. the Pacific Ring of Fire. d. the Pacific tectonic plate. 18. The Pacific Ring of Fire is also one of Earth s major a. flood zones. b. hurricane zones. c. drought zones. d. earthquake zones. 19. Many volcanoes are located along a. reduction zones. b. subduction zones. c. earthquake zones. d. continental zones. 20. One tectonic plate moves under another along a(n) a. reduction zone. b. subduction zone. c. earthquake zone. d. continental zone. Holt Earth Science 9 Volcanoes

4 21. When a plate of oceanic lithosphere meets one that consists of continental lithosphere, the oceanic lithosphere a. moves over the continental lithosphere. b. becomes continental lithosphere. c. moves beneath the continental lithosphere. d. moves through the continental lithosphere. 22. On the ocean floor, along the edge of the continent where the plate is subducted, a. a deep trench forms. b. a shallow trench forms. c. a narrow trench forms. d. a wide trench forms. 23. At subduction zones, the plate of continental lithosphere a. buckles and folds to form a mountain on the edge of the continent. b. buckles and folds to form a line of mountains along the edge of the continent. c. creates a line of earthquakes along the edge of the continent. d. creates a line of denser oceanic lithosphere. 24. As the oceanic plate sinks into the asthenosphere, water can combine with crust and mantle material a. and increase the melting point of the rock. b. and decrease the melting point of the rock. c. leaving the melting point of the rock unchanged. d. and cause rock to solidify. 25. When magma rises through the lithosphere to Earth s surface, a. volcanic mountains form along the tectonic plate. b. volcanic ash builds up along the tectonic plate. c. lava creates mountains along the tectonic plate. d. lava levels mountains along the tectonic plate. 26. When two plates with oceanic lithosphere at their boundaries collide, a. both plates subduct, forming a trench. b. one plate subducts, forming a trench. c. magma never reaches the surface. d. magma is trapped in the resulting trench. 27. If two plates with oceanic lithosphere collide, a. magma cannot form since no additional fluids are introduced into the mantle. b. magma forms as fluids are introduced into the mantle. c. magma cannot reach the surface. d. magma sinks deep into ocean trenches. Holt Earth Science 10 Volcanoes

5 28. When oceanic lithosphere subducts beneath oceanic lithosphere, magma rises to the surface to form an a. island chain. b. island cone. c. island arc. d. island trench. 29. An example of the early stages of an island arc are the a. Aleutian Islands. b. Faroe Islands. c. Channel Islands. d. islands of Japan. 30. As island arcs become larger, they join to form one landmass, such as the islands that make up the a. Solomon Islands. b. Aleutian Islands. c. Channel Islands. d. islands of Japan. 31. Explain what happens as magma comes to the surface where plates move apart at mid-ocean ridges. 32. Why don t humans notice most volcanic eruptions that take place along midocean ridges? 33. What is happening in Iceland, where volcanic eruptions happen along midocean ridges? Holt Earth Science 11 Volcanoes

6 Use the numbers 1 through 4 to show the sequence of volcano development in a hot spot. 34. Volcanoes form in the interior of a tectonic plate. 35. Columns of solid, hot material called mantle plumes rise and reach the lithosphere. 36. Magma rises to the surface and breaks through the overlying crust. 37. A mantle plume reaches the lithosphere, and spreads out. 38. Describe what happens to volcanic activity when the lithospheric plate above a mantle plume continues to drift. 39. Besides developing within the interior of a lithospheric plate, what is another way a hot spot may form? INTRUSIVE ACTIVITY In the space provided, write the letter of the description that best matches the term or phrase. 40. igneous rocks 41. plutons 42. dikes 43. batholiths a. rocks that form when magma cools b. small tubular plutons; may be only a few centimeters wide c. large formations of igneous rock, created by magma that does not reach Earth s surface, but cools and solidifies inside the crust d. large plutons that cover an area of at least 100 km 2 when exposed on Earth s surface Holt Earth Science 12 Volcanoes

7 Skills Worksheet Directed Reading Section: Volcanic Eruptions 1. Lava provides an opportunity for scientists to study a. the nature of Earth s inner core. b. the nature of Earth s tectonic plates. c. temperatures within Earth. d. the nature of Earth s crust and mantle. 2. By analyzing the composition of volcanic rocks, geologists have concluded that there a. is only one general type of magma. b. are two general types of magma. c. are three general types of magma. d. are two minerals in magma. 3. Magma or igneous rock that is rich in feldspar and silica and is generally light in color is called a. felsic. b. oceanic. c. mantle. d. mafic. 4. Magma or igneous rock that is rich in magnesium and iron and is generally dark in color is called a. felsic. b. oceanic. c. mantle. d. mafic. 5. Mafic rock commonly makes up a. oceanic crust. b. continental crust. c. Earth s inner core. d. tectonic plates. 6. Felsic rock commonly makes up a. oceanic crust. b. continental crust. c. Earth s inner core. d. tectonic plates. Holt Earth Science 13 Volcanoes

8 TYPES OF ERUPTIONS 7. The force of a volcanic eruption is affected by a. magma temperature. b. the distance from the top of the volcano to its base. c. the viscosity of magma. d. the geologic age of the volcano. 8. Mafic magmas, with low viscosity and runny lava, cause a. quiet eruptions. b. explosive eruptions. c. continuous eruptions. d. most volcanic eruptions. 9. Felsic magmas, with high viscosity and sticky lava, cause a. quiet eruptions. b. explosive eruptions. c. continuous eruptions. d. most volcanic eruptions. 10. Explosive eruptions are most likely to be caused by magma with a. small amounts of dissolved gases. b. large amounts of trapped, dissolved gases. c. any amount of dissolved gases. d. small amounts of dissolved rock. 11. Oceanic volcanoes commonly form from a. mafic magma. b. felsic magma. c. mafic or felsic magma. d. solid magma. 12. Eruptions from oceanic volcanoes are usually a. quiet eruptions. b. explosive eruptions. c. continuous eruptions. d. small eruptions. 13. When mafic lava cools rapidly it a. becomes less viscous. b. becomes explosive. c. forms a crust. d. shoots pyroclastic material. Holt Earth Science 14 Volcanoes

9 14. How does pahoehoe form? Why is the word pahoehoe used to describe this kind of volcanic rock? In the space provided, write the letter of the description that best matches the term or phrase. 15. pahoehoe 16. aa lava 17. blocky lava a. forms jagged, sharp chunks when it cools b. forms a smooth, ropy texture as it cools c. breaks into large chunks at the surface while hot lava continues to flow underneath 18. What is pyroclastic material? Use the terms from the following list to complete the sentences below. Each term may be used only once. volcanic bombs lapilli volcanic ash volcanic blocks volcanic dust 19. Pyroclastic particles less than 2 mm in diameter that mostly fall on the land that immediately surrounds the volcano are called. 20. Pyroclastic particles less than 0.25 mm in diameter that are so small they might travel around Earth in the upper atmosphere are called. 21. Large pyroclastic particles less than 64 mm in diameter that generally fall near the vent are called word meaning little stones., a name taken from a Latin Holt Earth Science 15 Volcanoes

10 22. Large clots of lava thrown out of an erupting volcano while red-hot, that spin through the air, cool, and develop a round or spindle shape are called. 23. The largest pyroclastic particles, which form from solid rock blasted from the volcano s vent, are called. TYPES OF VOLCANOES In the space provided, write the letter of the description that best matches the term or phrase. 24. volcanic cone 25. crater 26. shield volcano 27. cinder cone 28. composite volcano a. a volcanic cone that is broad at the base and has gently sloping sides b. structure formed by lava and pyroclastic material ejected during volcanic eruptions c. volcano with very steep slopes that are rarely more than a few hundred meters high and have angles close to 40 d. volcano made of alternating layers of hardened lava flows and pyroclastic material e. the funnel-shaped pit at the top of a volcanic vent CALDERAS 29. What is a caldera? 30. What are the three steps that most often occur in the formation of a caldera? 31. How did the caldera on the volcanic island of Krakatau form? Holt Earth Science 16 Volcanoes

11 32. How was Crater Lake in Oregon formed? PREDICTING VOLCANIC ERUPTIONS 33. One of the most important warning signals of volcanic eruptions is a. a change in earthquake activity around the volcano. b. a change in air pressure around the volcano. c. a change in animal behavior around the volcano. d. increased steepness of the volcanic cone. 34. What are three causes of small earthquakes that could signal a volcanic eruption? 35. What happens before an eruption that may cause the surface of the volcano to bulge outward? 36. What are three comparisons scientists make between a volcano s past behavior and its current behavior in order to help predict an eruption? 37. What are two problems scientists face in using a volcano s past behavior to predict a future eruption? Holt Earth Science 17 Volcanoes