In physical geography and geology, dome mountains such as the Black Hills are mainly formed as a result of which one of the following processes?

Introduction / Context:
Different types of mountains are classified according to the processes that formed them, such as folding, faulting, volcanic activity, and dome building. Dome mountains are a distinct type in which rock layers are arched upward into a dome like shape. Questions on this topic test knowledge of basic structural geology and landform evolution.

Given Data / Assumptions:

• The focus is on dome mountains.
• We must identify the geological process mainly responsible for their formation.
• Options include intrusion of magma, folding, friction at joints, and faulting.

Concept / Approach:
Dome mountains generally form when molten rock known as magma intrudes into the crust but does not reach the surface. The magma pushes overlying rock layers upward into a dome shape. Over time, erosion may strip away the upper layers, exposing the hardened intrusive body and leaving dome like mountains. This process is different from fold mountains, which arise when rock layers are compressed and folded, and from fault block mountains, which form due to movement along faults.

Step-by-Step Solution:
Step 1: Recall the definition of dome mountains as rounded, uplifted areas of rock.Step 2: Remember that such domes are produced when magma forces its way upward but cools and solidifies before erupting.Step 3: Understand that this magma intrusion creates a bulge, arching the rock layers above.Step 4: Check the answer choices for the process that mentions magma moving into existing rocks.Step 5: Identify Intrusion of magma as the process that matches this description.

Verification / Alternative check:
Standard geography textbooks list four main types of mountains: fold, block, volcanic, and dome. Under dome mountains, they usually mention examples like the Black Hills and describe magma pushing the crust upward without breaking through. This textbook description directly confirms that intrusion of magma is the correct process.

Why Other Options Are Wrong:
Folding refers to bending of rock layers due to compressional forces, typically forming long ridges and valleys in fold mountain belts rather than isolated domes. Friction at rock joints is a minor mechanical effect and does not create large scale mountain structures. Faulting produces block mountains when crustal blocks are uplifted or downthrown along faults, but this is not the defining process for dome mountains.

Common Pitfalls:
Learners sometimes lump all mountain types together and assume that folding is responsible for most of them. Another error is to associate any magma related process only with volcanoes and not with domes formed by intrusive bodies. Keeping the classification clear and linking dome mountains specifically with intrusive activity helps prevent confusion.

Final Answer:
Dome mountains are mainly formed by the Intrusion of magma, which pushes rock layers upward into a dome shape, so this is the correct option.