The Earth comprises three principal layers : the dense, iron-rich core, the mantle

            made of silicate rocks that are semimolten at depth, and the thin, solid-surface crust.

            There are two kinds of crust, a lower and denser oceanic crust and an upper, lighter

 Line     continental crust found over only about 40 percent of the Earth's surface. The rocks

 (5)       of the crust are of very different ages. Some continental rocks are over 3,000 million

            years old, while those of the ocean floor are less then 200 million years old. The crusts

            and the top, solid part of the mantle, totaling about 70 to 100 kilometers in thickness,

            at present appear to consist of about 15 rigid plates, 7 of which are very large. These

            plates move over the semimolten lower mantle to produce all of the major topographical

 (10)      features of the Earth. Active zones where intense deformation occurs are confined to

            the narrow, interconnecting boundaries of contact of the plates.

                There are three main types of zones of contact : spreading contacts where plates move

            apart, converting contacts where plates move towards each other, and transform

            contacts where plates slide past each other. New oceanic crust is formed along one or

 (15)      more margins of each plate by material issuing from deeper layers of the Earth's crust,

            for example, by volcanic eruptions of lava at midocean ridges. If at such a spreading

            contact the two plates support continents, a rift is formed that will gradually widen and

            become flooded by the sea. The Atlantic Ocean formed like this as the American and

            Afro-European plates moved in opposite directions. At the same time at margins of

 (20)      converging plates, the oceanic crust is being reabsorbed by being subducted into the

            mantle and remelted beneath the ocean trenches. When two plates carrying continents

            collide, the continental blocks, too light to be drawn down, continue to float and

            therefore buckle to form a mountain chain along the length of the margin of the plates.

            21. The word "comprises" in line 1 is closest in meaning to

              (A) adapts to

              (B) benefits from

              (C) consists of

              (D) focuses on

            22. According to the passage, on approximately what percent of the

                Earth's surface is the continental crust found?

              (A) 15

              (B) 40

              (C) 70

              (D) 100

            23. The word "which" in line 8 refers to

              (A) crusts

              (B) kilometers

              (C) plates

              (D) continents

            24. The word "intense" in line 10 is closest in meaning to

              (A) surface

              (B) sudden

              (C) rare

              (D) extreme

            25. What does the second paragraph of the passage mainly discuss?

              (A) The major mountain chains of the Earth

              (B) Processes that create the Earth's surface features

              (C) The composition of the ocean floors

              (D) The rates at which continents move

            26. Which of the following drawings best represents a transform contact (line 13-14)?

            27. The word "margins" in line 15 is closest in meaning to

              (A) edges

              (B) peaks

              (C) interiors

              (D) distances

            28. The word "support" in line 17 is closest in meaning to

              (A) separate

              (B) create

              (C) reduce

              (D) hold

            29. According to the passage, mountain ranges are formed then

              (A) the crust is remelted

              (B) two plates separate

              (C) a rift is flooded

              (D) continental plate collide

            30. Where in the passage does the author describe how oceans are formed?

              (A) Lines 3-4

              (B) Lines 6-8

              (C) Lines 16-18

              (D) Lines 19-21

Twitter