Question

set 1 — cross section model of earth’s surface and interior

1. which feature is commonly formed at a plate boundary where oceanic crust converges with continental crust?

(1) a mid - ocean ridge
(2) an ocean trench
(3) a transform fault
(4) new oceanic crust

1. the cross section below shows the direction of movement of an oceanic plate over a mantle hot spot, resulting in the formation of a chain of volcanoes labeled a, b, c, and d. the geologic age of volcano c is shown. what are the most likely geologic ages of volcanoes b and d?

image of a cross - section showing a mantle hot spot, plate motion, and volcanoes a, b, c, d with c being 8 million years old
(1) b is 5 million years old and d is 12 million years old.
(2) b is 2 million years old and d is 6 million years old.
(3) b is 9 million years old and d is 9 million years old.
(4) b is 10 million years old and d is 4 million years old.

1. hot spots are located

(1) only at mid - ocean ridges
(2) only on the continental plates
(3) only on the oceanic plates
(4) on both continental and oceanic plates

1. which evidence causes most scientists to believe that sea - floor spreading occurs at the mid - atlantic ridge?

(1) oceanic crust is oldest at the ridge.
(2) large sedimentary folds exist in the mantle near the ridge.
(3) oceanic crust on both sides of the ridge is less dense than continental crust.
(4) oceanic crust on both sides of the ridge shows matching patterns of reversed and normal magnetic polarity.

1. in which earth layer are most convection currents that cause sea - floor spreading thought to be located?

(1) crust (3) outer core
(2) upper mantle (4) inner core
image of a cross - section showing oceanic crust, continental crust, and magma

1. the rising magma most like originated from

(1) the melting of the continental crust
(2) the liquid inner core
(3) the subducting oceanic crust
(4) the liquid lower mantle

1. as the distance from the mid - atlantic ridge increases, the age of the ocean floor surface bedrock

(1) decreases
(2) increases
(3) decreases, then increases
(4) increases, then decreases

Explanation:

Question 1

When oceanic crust converges with continental crust, an ocean trench is formed (subduction zone). Mid - ocean ridges are at divergent boundaries, transform faults at transform boundaries, and new oceanic crust at divergent (mid - ocean ridge) boundaries.

The oceanic plate moves over the hot spot. Volcanoes further from the hot spot (in the direction of plate movement) are older, and closer are younger. Volcano C is 8 million years old. B is closer to A (active, youngest) than C, so B should be younger than 8 million. D is further from C (in the direction opposite to plate movement? Wait, plate movement is to the right. So A is youngest, then B, then C (8 myo), then D. Wait, no: the plate moves to the right, so the volcanoes are formed at the hot spot (A is active), then as the plate moves, B is formed, then C, then D. So the age should increase from A to D. Wait, the options: Let's re - evaluate. If C is 8 myo, then B (closer to A, formed before C? No, plate moves right, so A is now over hot spot, B was formed when the plate was to the left of C's position, C is now at 8 myo, D is to the right of C, formed after C? Wait, no, the diagram: A is active (magma from hot spot), B is a volcano, C is 8 myo, D is a volcano. The plate moves to the right. So the order of formation is A (youngest), then B, then C (8 myo), then D. So age increases from A to D. Wait, but the options: Option (4): B is 10 myo (older than C? No, that can't be). Wait, maybe I got the direction wrong. Maybe the hot spot is stationary, and the plate moves over it, so the volcanoes are formed in the order D, C, B, A (with A being the youngest, as it's over the hot spot now). So D was formed first, then C (8 myo), then B, then A (youngest). So age: D > C (8) > B > A. So B should be younger than 8, D older than 8. Option (1): B is 5 (younger than 8), D is 12 (older than 8) – that fits. Option (4): B is 10 (older than 8) – no. Option (2): B is 2 (younger), D is 6 (younger than 8) – no. Option (3): B and D same age – no. So correct is (1).

Hot spots can be located on both continental and oceanic plates (e.g., Yellowstone on North American (continental) plate, Hawaii on Pacific (oceanic) plate). So option (4) is correct.

Answer:

(2) an ocean trench

Question 2