Mountain formation can result when which of the following occurs?
a. Two oceanic plates collide.
c. Two oceanic plates spread apart.
d. None of the above.
The correct answer and explanation is:
The correct answer is a. Two oceanic plates collide.
Explanation:
Mountains form as a result of tectonic processes that involve the movement and interaction of Earth’s lithospheric plates. The specific mechanism by which mountain ranges are created depends on the type of plate boundaries involved. Let’s analyze the options provided:
- Two oceanic plates collide (Correct Answer): When two oceanic plates converge, they may collide, and one of the plates will usually be forced beneath the other in a process called subduction. This leads to the formation of a subduction zone, where the descending plate melts into the mantle, potentially causing volcanic activity. As the subducting plate continues to be forced downward, the overlying oceanic crust may buckle and fold, forming underwater mountain ranges, like the mid-ocean ridges. If the oceanic crust is pushed upward, volcanic island arcs may form, and this process can also contribute to the growth of mountains. A good example of this type of collision is the collision between the Pacific Plate and the smaller oceanic plates near Japan.
- Two oceanic plates spread apart: This scenario occurs at mid-ocean ridges, where oceanic plates move apart from each other. As the plates separate, magma rises from the mantle to create new oceanic crust, forming features such as underwater mountains or ridges, like the Mid-Atlantic Ridge. However, these features do not form typical mountain ranges because they are mostly submerged under the ocean and do not involve the compression of plates that leads to the formation of large, emergent mountains.
- None of the above: This option is incorrect because, as explained, the collision of oceanic plates can lead to mountain formation through subduction, volcanic activity, and the upward movement of crust.
In summary, mountains are formed when two oceanic plates collide (option a), leading to subduction, volcanic activity, and mountain-building processes.