Natural glass such as obsidian forms when
A) magma cools rapidly and very tiny crystals form.
B) magma cools too rapidly for crystals to form.
C) magma cools too slowly for crystals to form.
D) magma doesn't cool.
E) magma is reheated.
Correct Answer:
Verified
Q23: A magma composed of more than 65%
Q24: The viscosity of magma is dependent on
A)
Q25: Plutonic rocks
A) form below the surface of
Q26: Aphanitic, phaneritic and porphyritic are textural terms
Q27: Large crystals found in a fine-grained groundmass
Q29: Pegmatite refers to
A) an extremely coarse texture
B)
Q30: Volcanic necks form when
A) the magma abruptly
Q31: A granite would form under conditions that
Q32: A basalt would form under conditions that
Q33: If early-formed crystals settled out of a
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