1. Igneous Rocks:
* Magma Cooling and Solidification: These rocks form when molten rock (magma) cools and solidifies. This can happen:
* Intrusively: Inside the Earth's crust (e.g., granite).
* Extrusive: On the Earth's surface (e.g., basalt).
2. Metamorphic Rocks:
* Transformation of Existing Rocks: These rocks are formed when existing rocks (igneous, sedimentary, or even other metamorphic rocks) are subjected to intense heat and pressure. This causes the minerals and texture of the original rock to change.
* Contact Metamorphism: Occurs near intrusions of magma (e.g., marble).
* Regional Metamorphism: Occurs over large areas due to tectonic forces (e.g., slate).
3. Other Processes:
* Hydrothermal Activity: Hot, chemically active fluids can interact with existing rocks to alter their composition and create new minerals (e.g., some types of ore deposits).
* Volcanic Activity: Volcanic eruptions can deposit materials that solidify into various volcanic rocks (e.g., pumice, obsidian).
In summary:
* Igneous rocks form from cooling magma.
* Metamorphic rocks form from the transformation of existing rocks under heat and pressure.
* Other processes like hydrothermal activity and volcanic eruptions can also create non-sedimentary rocks.
