Question

igneous rock textures

1. which rock shown in the figure cooled the fastest?

a. fine - grained
b. porphorytic
c. glassy
d. coarse - grained

Explanation:

Igneous rock texture is related to cooling rate. Glassy igneous rocks form when magma cools extremely rapidly, preventing crystal formation. Fine - grained rocks cool faster than coarse - grained ones but slower than glassy rocks. Porphorytic rocks have a two - stage cooling process. So, glassy rocks cool the fastest.

Answer:

c. Glassy