* Recrystallization: Pressure causes existing mineral grains within the rock to become unstable and rearrange themselves into new, denser minerals. This process is called recrystallization. The new minerals often have a different chemical composition and physical properties than the original minerals.
* Texture Changes: Pressure can also cause the rock to deform and change its texture. This can lead to the development of foliation, which is a layered or banded appearance. For example, the metamorphic rock slate is formed from shale under pressure, and the pressure causes the clay minerals in the shale to align, creating the distinctive layered appearance.
* Mineral Transformations: High pressure can cause minerals to change their chemical composition. For example, the mineral calcite (found in limestone) can transform into the mineral aragonite under high pressure.
* Depth of Formation: Pressure is directly related to depth within the Earth. As rocks are buried deeper, the weight of overlying rocks creates immense pressure. This pressure, along with heat, is essential for the metamorphic process.
In summary, pressure is a key driver of metamorphic rock formation, causing changes in mineral composition, texture, and overall rock structure.
