Types of Faults in Geology

Summary

This video explains the dynamic nature of the Earth, focusing on the movement of tectonic plates and the resulting creation of faults. Faults occur when rocks break under stress, leading to earthquakes. The video describes three main types of faults: strike-slip, normal, and reverse faults. It also explains how the hanging wall and footwall differ in each fault type. Strike-slip faults involve horizontal movement, normal faults result from tension and cause the hanging wall to move down, while reverse faults are caused by compression, pushing the hanging wall up. The video concludes with examples like the San Andreas Fault and Basin and Range area.

Takeaways

• 😀 The Earth is constantly changing due to the movement of tectonic plates on the asthenosphere.
• 😀 Movement of tectonic plates creates stress in rocks, leading to fractures known as faults.
• 😀 Faults are cracks in the Earth’s surface, and the blocks on either side of the fault are called fault blocks.
• 😀 Earthquakes can occur when fault blocks move.
• 😀 There are three main types of faults: strike-slip faults, normal faults, and reverse faults.
• 😀 The hanging wall is the block of rock above a fault, and the footwall is the block below it.
• 😀 To identify the footwall and hanging wall: if you move your finger up along the fault surface, it will be on the hanging wall.
• 😀 In a strike-slip fault, blocks move past each other horizontally due to shear stress, often found at transform boundaries like the San Andreas Fault.
• 😀 Normal faults occur when the hanging wall moves down relative to the footwall, caused by tension stress at divergent boundaries like the Basin Range area.
• 😀 Reverse faults occur when the hanging wall moves up relative to the footwall, caused by compression stress at convergent boundaries like the San Gabriel Mountains.

Q & A

What causes stress in rocks on Earth?

Stress in rocks is caused by the movement of tectonic plates, which shift and move on the asthenosphere, creating pressure that may result in the breaking of rocks.

What are faults?

Faults are cracks or fractures in the Earth's surface that occur when rocks break in response to stress from tectonic plate movement.

What are fault blocks?

Fault blocks are the sections of rock on either side of a fault. These blocks can move independently, and when they do, it can trigger earthquakes.

What is the difference between a hanging wall and a footwall?

The hanging wall is the block of rock that is located above the fault, while the footwall is the block below the fault. The hanging wall is identified by having an angle less than 90 degrees at the top.

How can you identify the hanging wall and footwall?

You can identify the hanging wall by placing your finger on the fault surface and moving it up. The block above will be the hanging wall, while the block below is the footwall.

What causes a strike-slip fault?

A strike-slip fault occurs due to shear stress, which pushes the rocks horizontally but in opposite directions. This type of fault is commonly found along transform boundaries.

Where are strike-slip faults commonly found?

Strike-slip faults are typically found along transform boundaries, such as the San Andreas Fault.

What happens during a normal fault?

In a normal fault, the hanging wall moves down relative to the footwall. This type of fault occurs due to tension, which pulls the rock apart.

Where are normal faults commonly found?

Normal faults are common along divergent boundaries, such as the Basin and Range area.

What causes a reverse fault?

A reverse fault occurs when the hanging wall moves up relative to the footwall. This happens due to compression, which squeezes the rocks together.

Where are reverse faults commonly found?

Reverse faults are typically found in areas of compression, such as the San Gabriel Mountains.