What type of rock forms from the cooling and solidification of molten rock?

What type of rock forms from the cooling and solidification of molten rock?

• A. Igneous rock
• B. Sedimentary rock
• C. Metamorphic rock
• D. Obsidian

Answer: (A)

Cooling and solidification of molten rock produces igneous rock. When magma underground or lava at the surface cools, it hardens and crystallizes to form this rock type. The rate of cooling affects texture—slow cooling lets crystals grow larger, while rapid cooling can create a glassy texture, as seen in obsidian. Sedimentary rocks come from bits of other rocks or organic material pressed together, and metamorphic rocks form when existing rocks are altered by heat and pressure, not by molten rock cooling. Obsidian is a specific kind of igneous rock that forms from very fast cooling, but the general category being described is igneous rock.

Cooling and solidification of molten rock produces igneous rock. When magma underground or lava at the surface cools, it hardens and crystallizes to form this rock type. The rate of cooling affects texture—slow cooling lets crystals grow larger, while rapid cooling can create a glassy texture, as seen in obsidian. Sedimentary rocks come from bits of other rocks or organic material pressed together, and metamorphic rocks form when existing rocks are altered by heat and pressure, not by molten rock cooling. Obsidian is a specific kind of igneous rock that forms from very fast cooling, but the general category being described is igneous rock.