Question

With which of the three types of plate boundaries does normal faulting predominate? Thrust faulting? Strike-slip faulting?

Short answer

Normal: Divergent, Thrust: Convergent, Strike-slip: Transform.

Step-by-step solution

Understand Normal Faulting

In normal faulting, the crust is being pulled apart, causing the hanging wall to move downward relative to the footwall. This typically occurs at divergent plate boundaries where tectonic plates are moving away from each other.

Analyze Thrust Faulting

Thrust faulting involves the compression of the crust, causing the hanging wall to move upward relative to the footwall. This type of faulting is common at convergent plate boundaries where plates are moving toward each other.

Examine Strike-Slip Faulting

Strike-slip faulting occurs when two blocks of the crust slide past each other horizontally. This faulting is associated with transform plate boundaries, where plates slide sideways relative to each other.

Match Faulting with Plate Boundaries

Summarizing the types of faulting and corresponding plate boundaries: Normal faulting predominates at divergent boundaries, thrust faulting at convergent boundaries, and strike-slip faulting at transform boundaries.

Key concepts

normal faulting

Normal faulting occurs when the Earth's crust is being stretched or pulled apart. Imagine the crust as a loaf of bread being gently pulled in opposite directions until it starts to tear or split. In this scenario of normal faulting, the part of the crust called the "hanging wall" moves downward relative to the "footwall." This downward movement is due to the tensional forces that create space for the crust to move apart.

Normal faulting predominantly takes place at divergent plate boundaries. At these boundaries, tectonic plates are moving away from each other. You can think of it like two conveyor belts that are moving in opposite directions, which makes room between them. As these plates separate, they create conditions that lead to normal faulting. This is why regions with divergent boundaries, such as mid-ocean ridges, are common sites for normal faults.

thrust faulting

Thrust faulting occurs when the Earth's crust is being compressed, or pushed together, much like a piece of paper squeezed tightly in your hands. In this scenario, the "hanging wall" moves upward relative to the "footwall." This upward movement is caused by the compressional forces that push the crust into a smaller space.

This type of faulting is common at convergent plate boundaries where tectonic plates are moving toward each other. Imagine two massive vehicles in a head-on collision, crumpling as they impact. The immense pressure results in one plate being forced over the other. Thrust faults are the geological footprints left by these collisions. The Himalayas, for instance, were formed by thrust faulting from the collision of the Indian and Eurasian plates.

strike-slip faulting

Strike-slip faulting describes a scenario where two blocks of Earth's crust slide past one another horizontally, much like two people walking side by side in opposite directions. Unlike normal and thrust faults, which involve vertical movement, strike-slip faults feature lateral or sideways motion.

This type of faulting occurs at transform plate boundaries. At these boundaries, one plate moves sideways relative to its neighbor rather than towards or away. Think of two slices of toast being slid in opposite directions on a tabletop. The San Andreas Fault in California is a famous example of a strike-slip fault, where the Pacific Plate and the North American Plate slide past each other, sometimes causing earthquakes.

divergent boundaries

Divergent boundaries are tectonic plate boundaries where plates are moving apart. They are often found in oceanic regions, where they create mid-ocean ridges, but they can also exist within continents. As the plates diverge, magma rises from beneath the Earth's crust to fill the gap, creating new crust in the process.

These boundaries are the birthplaces of new seafloor and are characterized by frequent volcanic activity and earthquakes. Normal faulting predominates in these regions because of the tensional forces that pull the plates apart. As the plates separate, the Earth's crust thins and creates conditions ideal for normal faulting to occur.

convergent boundaries

Convergent boundaries are plate boundaries where tectonic plates are moving towards each other. When they collide, one of the following occurs: one plate is forced under another in a process called subduction, or they push against each other, causing uplift and mountain formation.

These boundaries are often associated with thrust faulting due to compressional forces that drive the plates together. The intense pressure and collision result in dramatic geological changes, such as mountain ranges or deep ocean trenches. The Andes mountain range in South America is an example of a location formed by the convergence of the South American Plate and the oceanic Nazca Plate.