Copyright by Holt, Rinehart and Winston s1

Chapter 13-2 Directed Reading Name: ______Period: ____

Chapter 13 Section 2: Volcanic Eruptions Pages 325- 330

_____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. Mafic rock commonly makes up a. oceanic crust. b. continental crust. c. Earth’s inner core. d. tectonic plates. ______4. Felsic rock commonly makes up a. oceanic crust. b. continental crust. c. Earth’s inner core. d. tectonic plates.

TYPES OF ERUPTIONS (page 325) _____ 5. 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. ______6. Felsic magmas, with high viscosity and sticky lava, cause a. quiet eruptions. b. explosive eruptions. c. continuous eruptions. d. most volcanic eruptions. ______7. 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. ______8. Oceanic volcanoes commonly form from a. mafic magma. b. felsic magma. c. mafic or felsic magma. d. solid magma In the space provided, write the letter of the description that best matches the term or phrase. ______9. pahoehoe a. forms jagged, sharp chunks when it cools ______10. aa lava b. forms a smooth, ropy texture as it cools ______11. blocky lava c. breaks into large chunks at the surface while hot lava continues to flow underneath 12. Pyroclastic particles less than 2 mm in diameter that mostly fall on the land that immediately surrounds the volcano are called ______. 13. Pyroclastic particles less than 0.25 mm in diameter that are so small they might travel around Earth in the upper atmosphere are called ______. 14. The largest pyroclastic particles, which form from solid rock blasted from the volcano’s vent, are called ______. TYPES OF VOLCANOES (page 328) ______15. volcanic cone a. a volcanic cone that is broad at the base and has gently sloping sides ______16. crater b. structure formed by lava and pyroclastic material ejected during volcanic eruptions ______17. shield volcano c. volcano with very steep slopes that are rarely more than a few hundred meters high and have angles close to 40° ______18. cinder cone d. volcano made of alternating layers of hardened lava flows and pyroclastic material ______19. composite volcano e. the funnel-shaped pit at the top of a volcanic

20. What is a caldera? PREDICTING VOLCANIC ERUPTIONS (page 329) 21. 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.

22. What are three causes of small earthquakes that could signal a volcanic eruption?