Which of the following is not a true statement about igneous rocks?
A) When magma rises slowly through the Earth's crust before erupting, crystals can form when the rest of the magma remains molten
B) The igneous rock texture described in "A" is called porphyry
C) If a rock has a porphyry texture, it will have interlocking crystals because it cooled for a long period of geologic time
D) Another term of volcanic is extrusive igneous rocks

Question

Quizplus · Accepted Answer

If a rock has a porphyry texture, it means that it has both fine-grained and coarse-grained crystals. This occurs when the magma initially cools slowly, creating larger crystals, before erupting and allowing the rest of the magma to cool quickly, creating smaller crystals. Therefore, a porphyry texture does not necessarily indicate that the rock cooled for a long period of geologic time, so statement C is not true.

Which of the Following Is Not a True Statement About