Question

Which type of mountain forms when rock layers are squeezed and bent? A. fault-block mountains B. upwarped mountains C. folded mountains D. volcanic mountains

Short answer

Folded mountains, option C.

Step-by-step solution

Understanding the Question

We need to determine which type of mountain forms when rock layers are compressed and bent.

Reviewing Mountain Types

There are four main types of mountains mentioned: fault-block, upwarped, folded, and volcanic. Each type forms through different geological processes.

Fault-Block Mountains

Fault-block mountains form when large areas of crust are broken and displaced vertically along faults. They are not formed by squeezing and bending of rock layers.

Upwarped Mountains

Upwarped mountains form when Earth's crust is pushed upward by forces inside the planet, often forming large dome structures rather than being squeezed and bent.

Folded Mountains

Folded mountains form through the process of compressional stress, which causes rock layers to squeeze and bend, creating folds. This matches the description in the question.

Volcanic Mountains

Volcanic mountains are formed from volcanic activity, often built up from erupted lava, ash, and other volcanic materials. They are not typically formed by squeezing and bending of rock layers.

Identifying the Correct Answer

Based on the review, the type of mountain that forms through squeezing and bending is 'Folded Mountains', which corresponds to option C.

Key concepts

Mountain Types

Mountains come in various shapes and sizes, and they form through different processes. There are four main types of mountains you should know about:

• **Fault-Block Mountains**
These mountains arise when large blocks of the Earth's crust are pulled apart and displaced vertically. Fault-block mountains are characterized by sharp and jagged peaks due to the faulting process.
• **Upwarped Mountains**
These mountains occur when the Earth's crust is pushed up by internal forces. The resulting structures are often broad domes or arches.
• **Folded Mountains**
These are formed by the intensive compressional forces that squeeze and bend rock layers. This process creates folds and layers, making them appear as wavy or ripple-like structures.
• **Volcanic Mountains**
These are built from successive lava flows and ash deposits from volcanic activity, often characterized by a central vent or crater.

The formation processes of these mountain types are key to understanding their characteristics and geological significance.

Geological Processes

Geological processes are natural mechanisms that shape the Earth's surface over time. They play a crucial role in forming different mountain types. Let's delve into some of these processes:

• **Tectonic Activity**
Ongoing movement of Earth's plates leads to tectonic activity, which is a primary driver in the formation of mountains. Two main processes linked to tectonic activity include plate convergence and divergence.

• **Folding**
When rock layers bend due to compressional stress, resulting in waves or folds in the Earth's crust. This is quintessential in the creation of folded mountains.

• **Faulting**
When stress on the Earth's crust leads to fractures or breaks, often displacing rock layers and forming fault-block mountains.

• **Volcanism**
The eruption and flow of magma contribute to creating volcanic mountains and also influence the topography drastically.

Understanding these geological mechanisms helps explain how different landforms, including various mountain types, come into existence.

Compressional Stress

Compressional stress is a fundamental geological force that leads to significant transformations in the Earth's crust. It occurs when rocks are squeezed by tectonic forces, causing them to crumple and fold.

• **Role in Mountain Building**
Compressional stress is notably responsible for the formation of folded mountains, where rock layers are pushed together and deformed. This process can result in the creation of spectacular mountain ranges like the Himalayas.

• **Types of Folds**
Common fold types include:
• Anticlines - upward arching folds.
• Synclines - downward, trough-like folds.
These folds can vary in severity from gentle waves to intense crumples, depending on the degree of stress applied.

• **Impact on Earth's Landscape**
Compressional stress affects not only mountains but also plays a role in forming valleys and basins. It changes the landscape dramatically and contributes to the dynamic nature of Earth's surface.

This type of stress is crucial in understanding how mountains form and evolve over geological time scales.