1. Base your answer to the following question on the cross section below and on your knowledge of Earth science. The cross section represents the distance and age of ocean-floor bedrock found on both sides of the Mid-Atlantic Ridge. According to the cross section, every 1 million years, the ocean floor bedrock moves approximately A) 20 km toward the Mid-Atlantic Ridge B) 20 km away from the Mid-Atlantic Ridge C) 40 km toward the Mid-Atlantic Ridge D) 40 km away from the Mid-Atlantic Ridge 2. The basaltic bedrock of the oceanic crust is classified as A) felsic, with a density of 2.7 g/cm 3 B) felsic, with a density of 3.0 g/cm 3 C) mafic, with a density of 2.7 g/cm 3 D) mafic, with a density of 3.0 g/cm 3 3. Compared to the continental crust, the oceanic crust is A) thicker B) more dense C) more granitic D) more felsic 4. Which combination of temperature and pressure is inferred to occur within Earth s stiffer mantle? A) 3500 C and 0.4 million atmospheres B) 3500 C and 2.0 million atmospheres C) 5500 C and 0.4 million atmospheres D) 5500 C and 2.0 million atmospheres 5. What happens to the density and temperature of rock within Earth s interior as depth increases? A) density decreases and temperature decreases B) density decreases and temperature increases C) density increases and temperature increases D) density increases and temperature decreases Page 1 6. In the diagram below, letters A and B represent locations near the edge of a continent. A geologist who compares nonsedimentary rock samples from locations A and B would probably find that the samples from location A contain A) more granite B) more basalt C) more fossils D) the same minerals and fossils 7. Compared to the oceanic crust, the continental crust is usually A) thicker, with a less dense granitic composition B) thicker, with a more dense basaltic composition C) thinner, with a less dense granitic composition D) thinner, with a more dense basaltic composition
8. On the map below, points A through D represent locations on Earth's surface. Which location is positioned over a mantle hot spot? A) A B) B C) C D) D 9. Which two features are commonly found at divergent plate boundaries? A) mid-ocean ridges and rift valleys B) wide valleys and deltas C) ocean trenches and subduction zones D) hot spots and island arcs 10.The convection currents responsible for moving tectonic plates occur in which Earth layer? A) crust B) rigid mantle C) stiffer mantle D) asthenosphere 11. The Aleutian Islands extend westward from southern Alaska to form the northern boundary of the Pacific Ocean. These volcanic islands were formed by the nearby A) subduction of a continental plate B) subduction of an oceanic plate C) divergence of a continental plate D) divergence of an oceanic plate 12. In which Earth layer are most convection currents that cause seafloor spreading thought to be located? A) crust B) asthenosphere C) outer core D) inner core 13. The map below shows California and a section of the San Andreas Fault. What is the primary geologic process occurring along the San Andreas Fault? A) transform movement B) spreading movement C) subduction D) convergence 14. A seismic station recorded the P-waves, but no S -waves, from an earthquake because S-waves were A) absorbed by Earth's outer core B) transmitted only through liquids C) weak and detected only at nearby locations D) not produced by this earthquake Page 2
Dynamic Crust Practice 15. Base your answer to the following question on the map below and on your knowledge of Earth science. The map shows the coast of the northwestern United States. The Explorer and Gorda ridges and plates are parts of the Juan de Fuca tectonic system. The arrow on which map best shows the direction of movement of the Juan de Fuca Plate in relation to the Juan de Fuca Ridge? A) B) C) D) Page 3
16. Which cross section best represents the convection currents in the mantle beneath the Peru-Chile Trench? A) B) C) D) 17. The block diagram below shows the boundary between two tectonic plates. Which type of plate boundary is shown? A) divergent B) convergent C) transform D) complex 18. Which part of Earth s interior is inferred to have convection currents that cause tectonic plates to move? A) rigid mantle B) asthenosphere C) outer core D) inner core Page 4
19. The cross section below represents a pattern of magnetic field reversals preserved in the igneous bedrock of the oceanic crust east of the Mid-Atlantic ridge. Which cross section best represents the magnetic field pattern west of the Mid-Atlantic ridge? A) B) C) D) 20. Base your answer to the following question on the passage below. Crustal Activity at Mid-Ocean Ridges Mid-ocean ridges are found at one type of tectonic plate boundary. These ridges consist of extensive underwater mountain ranges split by rift valleys. The rift valleys mark places where two crustal plates are pulling apart, widening the ocean basins, and allowing magma from the asthenosphere to move upward. In some cases, mid-ocean ridges have migrated toward nearby mantle hot spots. This explains why mid-ocean ridges and mantle hot spots are found together at several locations. Which type of tectonic plate boundary is located at mid-ocean ridges? A) convergent B) transform C) divergent D) complex Page 5
21. Base your answer to the following question on the map of the Mid-Atlantic Ridge shown below. Points A through D are locations on the ocean floor. Line XY connects locations in North America and Africa. In which cross section do the arrows best show the convection occurring within the asthenosphere beneath line XY? A) B) C) D) Page 6
22. Which cross section below best represents the crustal plate motion that is the primary cause of the volcanoes and deep rift valleys found at mid-ocean ridges? A) 24. Base your answer to the following question on the information and diagram below. At intervals in the past, the Earth's magnetic field has reversed. The present North magnetic pole was once the South magnetic pole, and the present South magnetic pole was once the North magnetic pole. A record of these changes is preserved in the igneous rocks that formed at mid-ocean ridges and moved away from the ridges. The diagram below represents the pattern of normal and reversed magnetic polarity in the igneous rocks composing the ocean crust on the east side of a mid-ocean ridge. B) C) D) Which diagram below best shows the pattern of normal and reversed polarity on the west side of the mid-ocean ridge? A) 23. The diagram below represents a cross section of a portion of the Earth's crust and mantle. LettersA, B, C, D and X identify locations within the crust. B) C) D) The age of oceanic crust increases along a line between location X and location A) A B) B C) C D) D Page 7
25. Base your answer to the following question on the map below, which shows the tectonic plate boundaries near the East African Rift. Arrows show relative tectonic plate movement. A region of Africa is crosshatched. Which diagram best represents the polarity of the magnetic field preserved in the ocean-floor bedrock found on both sides of the Mid-Indian Ridge? A) B) C) D) Page 8
26. Base your answer to the following question on the map below which shows mid-ocean ridges and trenches in the Pacific Ocean. Specific areas A, B, C, and D are indicated by shaded rectangles. Base your answers to questions 28 through 30 on the map below, which shows seismograph recording stations at locations A, B, and C. Location D is an earthquake epicenter. The distances from locations A and B to this epicenter are given in kilometers. Movement of the crustal plates shown in the diagram is most likely caused by A) the revolution of the Earth B) the erosion of the Earth's crust C) shifting of the Earth's magnetic poles D) convection currents in the Earth's mantle 27. The diagram below shows the collision of an oceanic plate and a continental plate. Collisions between oceanic plates and continental plates are thought to result primarily from A) hot liquid magma in the inner core B) convection currents in the mantle C) volcanic eruptions along coastlines D) meteor impacts in the ocean basins 28. Approximately how long did the S-wave take to travel from the epicenter to location A? A) 11 min 15 sec B) 9 min 35 sec C) 5 min 20 sec D) 4 min 20 sec 29. At which location is the arrival-time difference between the P-wave and the S-wave greatest? A) A B) B C) C D) D 30. Which statement best describes the igneous crustal bedrock below locations A, B, C, and D? A) The bedrock below D is mostly basalt; below A, B, and C, the bedrock is mostly granite. B) The bedrock below D is mostly granite; below A, B, and C, the bedrock is mostly basalt. C) The bedrock below A, B, C, and D is mostly basalt. D) The bedrock below A, B, C, and D is mostly granite. Page 9
31. Base your answer to the following question on the diagram below and on your knowledge of Earth science. The diagram represents a cut-away view of Earth's interior and the paths of some of the seismic waves produced by an earthquake that originated below Earth's surface. Points A, B, and C represent seismic stations on Earth's surface. Point D represents a location at the boundary between the core and the mantle. Seismic station A is 5000 kilometers from the epicenter. What is the difference between the arrival time of the first P-wave and the arrival time of the first S-wave recorded at this station? A) 2 minutes 20 seconds B) 6 minutes 40 seconds C) 8 minutes 20 seconds D) 15 minutes 00 second Page 10
32. The diagram below represents three seismograms showing the same earthquake as it was recorded at three different seismic stations, A, B, and C. Which statement correctly describes the distance between the earthquake epicenter and these seismic stations? A) A is closest to the epicenter, and C is farthest from the epicenter. B) B is closest to the epicenter, and C is farthest from the epicenter. C) C is closest to the epicenter, and A is farthest from the epicenter. D) A is the closest to the epicenter, and B is the farthest from the epicenter. Page 11