1. Heat and Pressure:
* Heat: Igneous rocks are buried deep within the Earth's crust or mantle. The intense heat from the Earth's interior causes the rock's minerals to become unstable and rearrange their structure.
* Pressure: The immense weight of overlying rock layers creates tremendous pressure on the buried igneous rock. This pressure also contributes to the instability of the minerals.
2. Chemical Reactions:
* Fluids: Hot fluids, often rich in dissolved minerals, circulate through the rock. These fluids act as catalysts, promoting chemical reactions and facilitating the transformation of minerals.
* Recrystallization: The heat, pressure, and fluids cause the existing minerals in the igneous rock to break down and recombine into new, more stable minerals. This process is called recrystallization.
3. Changes in Texture and Composition:
* Texture: Metamorphic rocks often develop a distinct texture. The pressure can cause minerals to align in a parallel fashion, giving the rock a foliated texture (like a layered cake). Other metamorphic rocks may exhibit a non-foliated texture.
* Composition: The chemical composition of the rock can change as new minerals form during the metamorphic process.
Example:
Imagine a granite (igneous rock) deep underground. Over time, the intense heat and pressure cause the quartz, feldspar, and mica in the granite to recrystallize. The mica minerals may align themselves, forming a foliated texture, resulting in a metamorphic rock called schist.
In summary, the transformation from igneous to metamorphic rock involves a complex interplay of heat, pressure, and chemical reactions that cause the existing minerals to recrystallize into new minerals with a distinct texture.
