1. Subduction and Metamorphism:
* Subduction: Sedimentary rock is dragged down into the Earth's mantle by tectonic plate movement. As it descends, it encounters increasing pressure and temperature.
* Metamorphism: The intense heat and pressure transform the sedimentary rock into metamorphic rock. The original sedimentary structures and minerals are often altered or destroyed, forming new minerals and textures. Examples include slate, marble, and gneiss.
2. Melting and Magma Formation:
* Melting: As the metamorphic rock descends even deeper, it begins to melt, forming magma. The composition of the magma will be influenced by the original sedimentary rock.
* Magma Chamber: The magma collects in a magma chamber, a large underground pool of molten rock.
3. Intrusive and Extrusive Igneous Rock Formation:
* Intrusive Igneous Rock: If the magma cools and solidifies beneath the Earth's surface, it forms intrusive igneous rock, like granite or diorite. These rocks have a coarse-grained texture because the magma cools slowly.
* Extrusive Igneous Rock: If the magma erupts onto the Earth's surface (volcanoes), it cools rapidly and forms extrusive igneous rock, like basalt or rhyolite. These rocks have a fine-grained texture due to rapid cooling.
4. Weathering and Erosion:
* Weathering: The igneous rocks at the surface are exposed to the elements – wind, rain, ice, and chemical reactions. These forces break down the igneous rocks into smaller pieces called sediments.
* Erosion: These sediments are then transported by wind, water, or ice, often being moved great distances.
5. Deposition and Compaction:
* Deposition: As the sediment is transported, it eventually settles in a new location, often in layers.
* Compaction: Over time, the weight of overlying sediment presses down on the lower layers, squeezing out water and air.
6. Cementation and Sedimentary Rock Formation:
* Cementation: Dissolved minerals in the groundwater precipitate between the sediment grains, binding them together. This process is called cementation.
* Sedimentary Rock: The cemented and compacted sediments form new sedimentary rocks. These rocks often contain fossils and show distinct layers.
Cycle Restart:
The newly formed sedimentary rock can now be uplifted, eroded, and deposited again, continuing the cycle. It can also be subducted back into the Earth's interior, repeating the process of metamorphism and igneous rock formation.
Key Point: The rock cycle is a continuous process with no set starting or ending point. Rocks transform from one type to another in a never-ending cycle driven by tectonic forces, weathering, erosion, and the internal heat of the Earth.
