Answer
Dikes and sills are both types of igneous intrusions, but they differ in their orientation and relationship to the surrounding rock layers. Here's a description of each using the appropriate terms:
Dikes:
- Dikes are tabular intrusions that cut across the layering or bedding planes of the surrounding rocks.
- They are typically vertical or near-vertical in orientation.
- Dikes are considered discordant intrusions because they cross the existing rock layers at an angle, creating a distinct boundary or contact between the dike and the surrounding rock.
- Dikes can vary in thickness from a few centimeters to several meters or more.
- They are often composed of coarse-grained or fine-grained igneous rocks.
- Dikes are characterized by their relatively massive structure, without significant layering or stratification.
Sills:
- Sills are also tabular intrusions, but they are concordant with the layering or bedding planes of the surrounding rocks.
- They are typically horizontal or near-horizontal in orientation.
- Sills are considered concordant intrusions because they parallel the existing rock layers and intrude between them without disrupting the layering.
- Sills have a tabular shape and extend laterally within the layering of the host rocks.
- They can have a relatively consistent thickness over a considerable distance.
- Sills are often composed of fine-grained or medium-grained igneous rocks.
- Sills can show layering or stratification, aligning with the bedding planes of the surrounding rocks.
In summary, dikes are discordant tabular intrusions that cut across the layering of the surrounding rocks, while sills are concordant tabular intrusions that parallel the layering of the host rocks. Dikes are typically vertical, while sills are generally horizontal. Dikes are massive in structure, while sills can exhibit layering or stratification.
Work Step by Step
Dikes and sills are both types of igneous intrusions, but they differ in their orientation and relationship to the surrounding rock layers. Here's a description of each using the appropriate terms:
Dikes:
- Dikes are tabular intrusions that cut across the layering or bedding planes of the surrounding rocks.
- They are typically vertical or near-vertical in orientation.
- Dikes are considered discordant intrusions because they cross the existing rock layers at an angle, creating a distinct boundary or contact between the dike and the surrounding rock.
- Dikes can vary in thickness from a few centimeters to several meters or more.
- They are often composed of coarse-grained or fine-grained igneous rocks.
- Dikes are characterized by their relatively massive structure, without significant layering or stratification.
Sills:
- Sills are also tabular intrusions, but they are concordant with the layering or bedding planes of the surrounding rocks.
- They are typically horizontal or near-horizontal in orientation.
- Sills are considered concordant intrusions because they parallel the existing rock layers and intrude between them without disrupting the layering.
- Sills have a tabular shape and extend laterally within the layering of the host rocks.
- They can have a relatively consistent thickness over a considerable distance.
- Sills are often composed of fine-grained or medium-grained igneous rocks.
- Sills can show layering or stratification, aligning with the bedding planes of the surrounding rocks.
In summary, dikes are discordant tabular intrusions that cut across the layering of the surrounding rocks, while sills are concordant tabular intrusions that parallel the layering of the host rocks. Dikes are typically vertical, while sills are generally horizontal. Dikes are massive in structure, while sills can exhibit layering or stratification.
