Here's how it works:
* Heat: The intruding magma or lava is significantly hotter than the surrounding rock. This intense heat causes the pre-existing minerals in the rock to recrystallize and form new minerals that are stable at higher temperatures.
* Chemical Reactions: The magma or lava also contains various chemical elements and fluids that can react with the surrounding rock. These reactions can alter the mineral composition of the rock and create new minerals.
* Pressure: The intrusion of magma or lava can also apply pressure to the surrounding rock. This pressure can cause the rock to become denser and more compact.
Types of Contact Metamorphism:
* Aureole: The zone of metamorphic rock surrounding the intrusion is called an aureole. The intensity of the metamorphism decreases with distance from the intrusion.
* Hornfels: A common type of contact metamorphic rock, characterized by a fine-grained texture and a lack of foliation.
* Skarn: A type of contact metamorphic rock formed by the interaction of magma or lava with carbonate rocks.
Examples of Contact Metamorphism:
* Granite intrusions: Granitic intrusions often create large aureoles of contact metamorphic rocks around them.
* Volcanic eruptions: Lava flows can also cause contact metamorphism in the rocks they flow over.
* Dikes and sills: These small intrusions of magma can also cause contact metamorphism on a smaller scale.
In summary, contact metamorphism is a localized type of metamorphism that occurs when hot magma or lava intrudes into existing rock. It results in changes in the mineral composition, texture, and structure of the rock, often creating distinctive contact metamorphic rocks like hornfels and skarn.
