Which Rocks term is correctly associated with rock classification: “an extrusive igneous rock”, and also with “formed by rapid cooling of lava at the surface”?

Correct Answer: Option A — Basalt. Basalt is correct because it is an extrusive igneous rock. Basalt is also associated with formed by rapid cooling of lava at the surface. A further identifying fact is that Basalt is dark-coloured and fine-grained. Another useful fact is that Basalt is associated with common in oceanic crust and lava plateaus. Why the other options are incorrect: Option B — Pumice: It is a vesicular volcanic rock and is associated with formed when gas-rich lava cools rapidly; those are the identifying facts of Pumice. Option C — Obsidian: It is a volcanic glass and is associated with formed by extremely rapid cooling of silica-rich lava; those are the identifying facts of Obsidian. Option D — Sandstone: It is a clastic sedimentary rock and is associated with formed by compaction and cementation of sand grains; those are the identifying facts of Sandstone. Exam Takeaway: Link Basalt with “an extrusive igneous rock” and “formed by rapid cooling of lava at the surface” for quick revision.