Intrusive Igneous Rocks (Plutonic Rocks)
* Batholiths: These are enormous, irregularly shaped bodies of intrusive igneous rock, often formed by the accumulation of multiple magma chambers. They are found in mountain ranges formed by tectonic uplift, such as the Sierra Nevada in California.
* Stocks: Smaller versions of batholiths, stocks are often found in association with batholiths.
* Dikes: These are tabular intrusions that cut across existing rock layers. They are often found in areas where magma is rising towards the surface, such as in volcanic regions.
* Sills: These are tabular intrusions that are parallel to existing rock layers. They can be found in areas where magma has flowed along bedding planes.
* Laccoliths: Dome-shaped intrusions that uplift the overlying strata. They often form in areas where magma has been injected into a layer of sedimentary rock.
Extrusive Igneous Rocks (Volcanic Rocks)
* Volcanoes: The most common setting for extrusive igneous rocks. Volcanoes can be found in various settings, including:
* Convergent Plate Boundaries: Where oceanic and continental plates collide, volcanic arcs form (e.g., the Andes Mountains).
* Divergent Plate Boundaries: Where plates move apart, mid-ocean ridges form, and volcanic activity occurs along these ridges.
* Hot Spots: Areas of volcanic activity that are not associated with plate boundaries (e.g., Hawaii).
* Lava Flows: Outpourings of molten rock that spread across the land surface. They are common in volcanic regions.
* Pyroclastic Flows: Fast-moving, hot currents of gas and volcanic debris that can travel at speeds up to 450 miles per hour. They are typically associated with explosive volcanic eruptions.
Important Note: The geographic setting of igneous rock formation is directly linked to plate tectonics. The movement of Earth's tectonic plates creates the conditions that allow for the melting of rock and the formation of magma, which in turn leads to the formation of intrusive and extrusive igneous rocks.
