1. Heat and Pressure:
* Heat: This comes from the Earth's internal heat, magma intrusions, or friction caused by tectonic plate movement.
* Pressure: The weight of overlying rock layers and tectonic forces create immense pressure.
2. Recrystallization:
* The heat and pressure cause the minerals in the original rock to break down and rearrange, forming new minerals that are more stable under the new conditions. This process is called recrystallization.
* The original rock's texture and composition are altered.
3. Change in Texture:
* The intense pressure can cause the minerals to align in a specific direction, giving the rock a foliated texture. This means the rock develops layers or bands. Examples include slate, schist, and gneiss.
* If the pressure is more evenly distributed, the rock may develop a non-foliated texture. This means the rock has no layers or bands. Examples include marble and quartzite.
4. Types of Metamorphism:
* Contact Metamorphism: Occurs when rocks are heated by contact with magma or lava. This is a local process and creates rocks with a non-foliated texture.
* Regional Metamorphism: Takes place over large areas and is caused by intense heat and pressure associated with tectonic plate collisions. This creates rocks with a foliated texture.
Examples:
* Marble: Formed by the metamorphism of limestone.
* Quartzite: Formed by the metamorphism of sandstone.
* Slate: Formed by the metamorphism of shale.
* Gneiss: Formed by the metamorphism of granite or other metamorphic rocks.
Key Points:
* Metamorphic rocks are formed through transformation of existing rocks.
* Heat and pressure are the driving forces behind recrystallization, which alters the rock's mineral composition and texture.
* The type of metamorphism (contact or regional) influences the texture of the resulting rock.
Let me know if you'd like to delve into any of these aspects in more detail!
