How can a sill be distinguished from a lava flow?
A)A sill is generally finer-grained than a lava flow.
B)Rocks above and below a sill will show evidence of heating,but only the rocks below a lava flow will show evidence of heating.
C)Sills generally have vesicles; lava flows generally do not have vesicles.
D)Sills generally overlie soils; lava flows do not generally overlie soils.

Question

Quizplus · Accepted Answer

Sills are intrusive igneous bodies that form when magma intrudes parallel to layers of rock, causing heating and metamorphism in the surrounding rock both above and below the sill. In contrast, lava flows are extrusive, cooling on the surface, so only the rock below would show evidence of heating.

How Can a Sill Be Distinguished from a Lava Flow