Dike

Definition

A dike is a geological feature formed by the intrusion of magma into existing rock layers, typically creating a vertical or near-vertical wall of igneous rock. Dikes are important indicators of magma generation processes as they provide insight into the movement and behavior of magma beneath the Earth's surface, reflecting the conditions that lead to volcanic activity.

5 Must Know Facts For Your Next Test

1. Dikes are often found in swarms, indicating that multiple magma injections occurred during a specific geological period.
2. They can vary greatly in thickness, ranging from a few centimeters to several meters, and can extend for long distances.
3. The material that forms a dike is typically composed of basalt or other volcanic rock, depending on the composition of the originating magma.
4. Dikes can disrupt existing rock formations, causing fractures and changes in mineral distribution, which helps geologists understand past volcanic activity.
5. In some cases, dikes can be exposed at the surface due to erosion, revealing their structure and providing valuable data for volcanologists studying past eruption patterns.

Review Questions

• How do dikes provide evidence for the processes involved in magma generation and movement?
  • Dikes serve as key indicators of how magma travels through the Earth's crust by showing where it has intruded into existing rock layers. The orientation and structure of dikes can reveal the pressure conditions and pathways that magma took during its ascent. Additionally, studying the composition of dikes allows scientists to infer details about the source magma and its evolution, providing insight into volcanic activity in a given area.
• Discuss how dikes differ from sills and their implications for understanding igneous intrusions.
  • Dikes are vertical or near-vertical intrusions while sills are horizontal sheets formed when magma intrudes between sedimentary layers. This fundamental difference in orientation affects how each structure interacts with surrounding rock. Understanding these differences helps geologists determine the history of magma movement and intrusion mechanisms within an area, which is crucial for assessing volcanic hazards and potential eruption sites.
• Evaluate the role of dikes in understanding past volcanic activity and how this knowledge can inform future volcanic risk assessments.
  • Dikes play a significant role in reconstructing past volcanic activity by providing a physical record of magma movements and eruptive history. By analyzing the distribution, composition, and age of dikes, volcanologists can identify patterns in volcanic behavior and potential triggers for eruptions. This information is vital for future risk assessments as it helps predict how similar volcanic systems may behave under current geological conditions, ultimately aiding in disaster preparedness and mitigation strategies.

Related terms

Sill:

A sill is a type of igneous intrusion that forms when magma intrudes between existing layers of sedimentary rock, creating a horizontal or nearly horizontal sheet of rock.

Pluton: A pluton is a large body of intrusive igneous rock that forms from the slow crystallization of magma beneath the Earth's surface.

Volcanism: Volcanism refers to the processes and phenomena associated with the movement of magma from the Earth's interior to its surface, resulting in volcanic eruptions and the formation of various volcanic features.