Question

question 22
what connection does the author make between magma and its cooling rate?
a. magma that cools quickly creates igneous rocks that are softer.

b. magma that cools slowly creates igneous rocks that are more valuable.

c. the magma’s cooling rate determines the size of crystals that are formed.

d. the magma’s cooling rate determines whether sedimentary or igneous rocks form.

Explanation:

To solve this, we analyze each option:

• Option A: The text doesn't mention hardness/softness related to magma cooling speed. Eliminate A.
• Option B: The text doesn't discuss the value of rocks formed from slow - cooling magma. Eliminate B.
• Option C: The passage says "When magma cools rapidly, usually at or near the Earth’s surface, the crystals are extremely small, and a fine - grained rock results. When magma cools slowly, usually at depths of thousands of feet, crystals grow from the molten liquid, and a coarse - grained rock forms." This shows that the cooling rate of magma determines the size of the crystals in igneous rocks. This option matches the text.
• Option D: The text states that igneous rocks form from cooled and solidified melted rock (magma), and sedimentary rocks form at the Earth's surface from sediments. The cooling rate of magma doesn't determine if a rock is sedimentary or igneous. Eliminate D.

Answer:

C. The magma's cooling rate determines the size of crystals that are formed.