Match Each Term With Its Best Definition
In geology, igneous intrusions are bodies of rock that form when magma or lava cools and solidifies below the surface of the Earth. There are four main types of igneous intrusions: plutons, sills, dikes, and laccoliths.
Plutons are the largest type of igneous intrusion. They are typically formed when magma cools and solidifies deep underground, where it is not exposed to the elements. Plutons can be either concordant or discordant. Concordant plutons are aligned with the surrounding rock, while discordant plutons cut across the surrounding rock.
Sills are smaller than plutons, and they are typically formed when magma flows between existing layers of rock. Sills are typically parallel to the surrounding rock.
Dikes are even smaller than sills, and they are typically formed when magma flows into fractures in the surrounding rock. Dikes can be either vertical or horizontal.
Laccoliths are dome-shaped intrusions that are formed when magma flows between layers of rock and pushes up the overlying rock. Laccoliths are typically larger than sills, but smaller than plutons.
Matching Terms with Definitions
The following table matches each term with its best definition:
| Term | Definition |
|---|---|
| Pluton | A large, discordant igneous intrusion that forms deep underground |
| Sill | A smaller, concordant igneous intrusion that forms between existing layers of rock |
| Dike | A small, discordant igneous intrusion that forms in a fracture in the surrounding rock |
| Laccolith | A dome-shaped igneous intrusion that forms when magma flows between layers of rock and pushes up the overlying rock |
Questions
Here are some questions that you can use to test your understanding of igneous intrusions:
- What is the difference between a pluton and a sill?
- What is the difference between a dike and a laccolith?
- What are the four main types of igneous intrusions?
- What are the different ways that igneous intrusions can form?
- What are the different shapes and sizes of igneous intrusions?
Answers
Here are the answers to the questions above:
- A pluton is a larger, discordant igneous intrusion that forms deep underground, while a sill is a smaller, concordant igneous intrusion that forms between existing layers of rock.
- A dike is a small, discordant igneous intrusion that forms in a fracture in the surrounding rock, while a laccolith is a dome-shaped igneous intrusion that forms when magma flows between layers of rock and pushes up the overlying rock.
- The four main types of igneous intrusions are plutons, sills, dikes, and laccoliths.
- Igneous intrusions can form in a variety of ways, including:
- Magma rising from the mantle and cooling below the surface of the Earth
- Lava flowing from a volcano and cooling below the surface of the Earth
- Magma being injected into fractures in the surrounding rock
- Igneous intrusions can have a variety of shapes and sizes, depending on how they form. Plutons are typically large and irregular in shape, while sills are typically thin and flat, and dikes are typically narrow and vertical. Laccoliths are typically dome-shaped.
Additional Information
In addition to the four main types of igneous intrusions, there are a number of other, less common types of intrusions. These include:
- Stocks: Smaller plutons that are typically less than 1 kilometer in diameter
- Laccoliths: Dome-shaped intrusions that are larger than sills but smaller than plutons
- Lopoliths: Basin-shaped intrusions that are formed when magma flows into a depression in the Earth’s crust
- Pylon: A vertical intrusion that is formed when magma flows into a fracture and then cools and solidifies
- Batolith: A very large pluton that is typically more than 100 kilometers in diameter
Igneous intrusions play an important role in the formation of the Earth’s crust. They can contribute to the formation of mountains, volcanoes, and other geological features.