Here's why:
* Contact: The term "contact" refers to the direct contact between the hot magma and the surrounding rocks.
* Metamorphism: This means that the existing rocks are transformed into new rocks with different mineral compositions and textures due to the heat and sometimes the fluids from the magma.
Key characteristics of contact metamorphism:
* High temperatures: The magma provides a direct source of heat, causing the rocks to recrystallize.
* Limited area: The effects of contact metamorphism are typically localized around the intrusion, creating a zone of altered rocks called a contact aureole.
* High pressure: While pressure is not as significant as in regional metamorphism, the intrusion itself can create localized pressure.
* Chemical changes: The magma can release fluids and volatile compounds that react with the surrounding rocks, leading to chemical changes.
Examples of rocks formed by contact metamorphism:
* Hornfels: A hard, fine-grained rock typically formed from shale or mudstone.
* Marble: Formed from the recrystallization of limestone.
* Skarn: A metamorphic rock formed when limestone or dolostone reacts with fluids from the magma.
Important note: The type of metamorphic rock produced depends on the original rock type, the temperature, and the composition of the magma.
