How does the time it takes to form metamorphic rock compare to the time it takes to form extrusive igneous rock?

The formation of both metamorphic and extrusive igneous rocks involves processes that occur over significant geological timescales. However, the time it takes for each to form can vary greatly depending on specific conditions and processes involved.

1. Formation of Extrusive Igneous Rock: Extrusive igneous rocks form when magma reaches the Earth's surface, either through a volcano or a fissure, and cools rapidly. This rapid cooling doesn't allow large crystals to form, resulting in a fine-grained rock like basalt. The process can take from a few days to a few years depending on the size of the magma flow.

2. Formation of Metamorphic Rock: Metamorphic rocks form from existing rocks that are subjected to high temperatures, high pressures, or both, but without melting. This process, known as metamorphism, can take millions of years. The existing rock, or parent rock, is altered physically and chemically resulting in a metamorphic rock. The rate of metamorphism can be influenced by the temperature, pressure, and the type of parent rock.

In comparison, the formation of metamorphic rocks generally takes much longer than the formation of extrusive igneous rocks. However, it's important to note that these processes occur on geological timescales and can vary greatly depending on specific conditions.