Bot GPT 4-o mini The two main types of rocks that form from sub-surface events are igneous rocks and metamorphic rocks. Here's how each type is formed:
1. Igneous Rocks
- Formation Process: Igneous rocks are formed from the cooling and solidification of molten rock material called magma (when below the surface) or lava (when it erupts onto the surface).
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Types of Formation:
- Intrusive igneous rocks (or plutonic rocks) form when magma cools slowly beneath the Earth's surface, allowing large crystals to develop. An example of this type is granite.
- Extrusive igneous rocks (or volcanic rocks) form when lava cools quickly on the surface, resulting in smaller crystals. An example of this type is basalt.
2. Metamorphic Rocks
- Formation Process: Metamorphic rocks are formed when existing rocks (either igneous, sedimentary, or other metamorphic rocks) undergo changes due to high temperature, pressure, and/or chemically active fluids without melting. This process is known as metamorphism.
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Types of Metamorphism:
- Contact metamorphism occurs when rocks are heated by nearby molten magma or lava.
- Regional metamorphism occurs over wide areas due to tectonic forces, where rocks are subjected to great pressure and temperature over long periods.
Examples of metamorphic rocks include schist, gneiss, and marble.
In summary, igneous rocks form from the solidification of molten material, while metamorphic rocks form through the alteration of existing rocks under conditions of heat and pressure.
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