Dike

Definition

A dike is a vertical or near-vertical wall of igneous rock that forms when magma intrudes into existing rock layers and solidifies. Dikes can vary in thickness and extend for long distances, often cutting across sedimentary strata, and are important indicators of the geological processes involved in magma generation and movement.

5 Must Know Facts For Your Next Test

1. Dikes are formed by the movement of magma that forces its way into cracks and fissures in pre-existing rock layers, often under high pressure.
2. They can provide valuable information about the history of volcanic activity and tectonic movements in an area, serving as indicators of past geological processes.
3. Dikes can vary widely in composition, with some being made of basaltic magma while others may consist of more evolved magmas, reflecting different source materials.
4. In many cases, dikes are associated with larger igneous bodies, such as batholiths or stocks, which may be connected to the same magma source.
5. The study of dikes can help geologists understand the plumbing systems of volcanoes and the dynamics of magma generation and transport within the Earth's crust.

Review Questions

• How do dikes form, and what role do they play in understanding magma movement within the Earth's crust?
  • Dikes form when magma intrudes into cracks and fissures in existing rock layers, solidifying into vertical walls as it cools. They are crucial for understanding magma movement because their orientation and composition can reveal insights into the pressures and pathways involved in igneous intrusion. By studying dikes, geologists can trace the history of volcanic activity and assess how magma travels through the crust, providing a clearer picture of the geological processes at work.
• Compare and contrast dikes with sills in terms of their formation and geological significance.
  • Dikes and sills are both types of igneous intrusions but differ primarily in their orientation. Dikes are vertical or steeply inclined sheets formed by magma that cuts across existing rock layers, while sills are horizontal intrusions that occur between layers. Both formations provide valuable information about volcanic activity; however, dikes often indicate more dynamic conditions involving significant pressure changes, while sills tend to reflect less explosive magmatic processes. Understanding both structures enhances our comprehension of subsurface magma behavior.
• Evaluate the significance of studying dikes in relation to volcanic hazards and resource exploration.
  • Studying dikes is significant for assessing volcanic hazards because they can indicate areas of past volcanic activity and potential future eruptions. The presence and characteristics of dikes help geologists understand the plumbing systems beneath volcanoes, which is crucial for predicting eruptions. Additionally, dikes may host valuable mineral deposits formed from the cooling and crystallization of minerals in the magma. Thus, recognizing dike formations contributes to both hazard assessment and resource exploration efforts.

Related terms

Sill: A sill is a horizontal or gently inclined sheet of igneous rock that forms when magma intrudes between existing layers of rock, typically parallel to the layering.

Magma Chamber: A magma chamber is a large underground pool of molten rock located beneath the surface, where magma accumulates before it rises to form volcanic features like dikes and sills.

Volcanic Plug: A volcanic plug is a solidified lava that fills the vent of a volcano, often resulting in a steep-sided hill or mountain after erosion exposes the hardened material.