A scientist identifies a rock sample as andesite. Why did he do so?
A) He observed that the rock has a lot of silica, making it mafic.
B) He observed that the rock has a lot of silica, making it ultra-mafic.
C) He observed that the rock has a decent amount of silica, making it intermediate.
D) He observed that the sample has little silica, making it felsic.

Question

Quizplus · Accepted Answer

Andesite is an intermediate rock type, meaning it has a decent amount of silica (between 52-63%). The other options (A, B, D) describe rocks with different silica contents and therefore cannot be correct for andesite.

A Scientist Identifies a Rock Sample as Andesite