Question

1. the texture formed when magma has a large amount of dissolved gases and cools very quickly is ____.

○ glassy
○ coarse - grained
○ porphyritic
○ vesicular

Explanation:

• Glassy texture forms from extremely rapid cooling of magma with little to no dissolved gas, creating non-crystalline rock like obsidian.
• Coarse-grained texture develops from slow cooling underground, allowing large mineral crystals to form (e.g., granite).
• Porphyritic texture occurs when magma cools in two stages: slow initial cooling forming large crystals, followed by rapid cooling forming small surrounding crystals.
• Vesicular texture forms when gas-rich magma cools quickly at the surface; the trapped dissolved gases create small cavities (vesicles) in the rock, such as in scoria or pumice. This matches the description of gas-rich magma cooling very quickly.

Answer:

D. vesicular