Question

Fill in the blanks with the correct vocabulary word or words. Magma squeezed into a vertical crack across rock layers is called \(\mathrm{a}(\mathrm{n})\) __________.

Short answer

dike.

Step-by-step solution

Understand the Context

Before selecting the vocabulary word, it's crucial to understand the geological context. Magma is molten rock beneath the Earth's surface. When magma intrudes into the existing rock formations in specific ways, it forms different geological structures.

Identify the Geologic Structure

Review the key terms associated with different types of igneous intrusions. Magma that cuts across existing rock layers in a vertical manner is usually referred to as a 'dike.' This is distinct from a 'sill,' which is a horizontal intrusion.

Fill in the Blank

Given the definition, the correct terminology that matches 'magma squeezed into a vertical crack across rock layers' is 'dike.' Therefore, the blank should be filled with the word 'dike.'

Key concepts

Magma

Magma is a fascinating and critical component of Earth's geology. It refers to molten rock located beneath the Earth’s surface. This molten material results from the intense heat within the Earth’s interior, which melts rocks. Magma is composed of:

• Liquid base
• Mineral crystals
• Dissolved gases

These components result in a high-temperature liquid that can form into solid rocks upon cooling.
Magma plays a crucial role in the rock cycle by forming igneous rock through cooling and solidification. Notably, when magma exits the Earth's surface, it is termed 'lava.' The formation of different geological structures depends on how and where magma cools and solidifies, leading to various formations including igneous intrusions.

Igneous Intrusions

Igneous intrusions are geological structures formed when magma cools and solidifies beneath the Earth's surface. This process intrudes and creates formations within pre-existing rock layers. These intrusions can vary greatly in size and shape, typically depending on the specific pathway that the magma follows through cracks and spaces within the rock.
Describing igneous intrusions includes:

• Dikes: Vertical or steeply-inclined structures that cut across rock layers.
• Sills: Horizontal formations that form parallel to existing layers.

Igneous intrusions solidify slowly beneath the surface, allowing larger mineral crystals to form. This process results in coarse-grained textures found in rocks such as granite and diorite. Understanding these intrusions helps geologists decipher past geological events and the Earth’s internal processes.

Dike

A dike is a type of igneous intrusion. It forms when magma inserts into a vertical fracture, cutting through existing rock layers. Unlike horizontal intrusions like a sill, dikes disrupt the layering of rocks, often appearing as narrow, upright columns or walls.
Key characteristics of dikes include:

• Vertical orientation
• Thick, wall-like appearance
• Composition similar to surrounding igneous rocks

Dikes can provide important clues about the history of volcanic activity in an area. Their vertical formation is a testament to the intense force and pressure under which the magma moves. Dikes are often more resistant to erosion compared to surrounding rock layers, causing them to stand out in the landscape.

Rock Layers

Rock layers, also known as strata, are different levels of sedimentary, metamorphic, or igneous rocks piled upon one another over time. These layers help geologists understand the chronological history of the Earth, indicating environments where each layer was formed.
Essential aspects of rock layers include:

• Composition: Varying types such as sedimentary, igneous, or metamorphic
• Thickness: Varies greatly based on deposition rates and environmental factors
• Fossil content: Sedimentary layers may contain fossils providing insights into past life forms

The positioning and orientation of these layers are crucial for determining geological events such as tectonic activity and erosion. When features like dikes intrude across rock layers, they can drastically change the landscape and provide insight into past geological movements.