What condition results in magma cooling and forming a "glassy" igneous rock?

A)

extremely slow cooling

B)

cooling in the presence of oxygen

C)

extremely rapid cooling

D)

partial melt cooling

E)

extremely high pressure

Your correct answer is C) extremely rapid cooling

C

Explanation:

Glassy or vitreous textures occur during some volcanic eruptions when the lava is quenched so rapidly that crystallization cannot occur. The result is a natural amorphous glass with few or no crystals. As magma cools slowly the minerals have time to grow and form large crystals.