Obsidian is an igenous rock with a glassy appearance and minimal crystal growth. What accounts for this?
A) Obsidian is an intrusive igneous rock that cooled slowly beneath the Earth's surface, result in little crystal growth.
B) Obsidian is an extrusive igneous rock that cooled slowly on the Earth surface, resulting in little crystal growth.
C) Obsidian is an extrusive igneous rock that cooled very slowly on the Earth surface, resulting in little crystal growth.
D) Obsidian is an intrusive igneous rock that cooled rapidly beneath the Earth's surface, result in little crystal growth.

Question

Quizplus · Accepted Answer

Obsidian is an extrusive igneous rock that cools rapidly on the Earth's surface, resulting in very little time for crystals to form. As a result, obsidian has a glassy appearance and minimal crystal growth. Intrusive igneous rocks, on the other hand, cool slowly beneath the Earth's surface, allowing for larger crystals to form.

Obsidian Is an Igenous Rock with a Glassy Appearance and Minimal