Types of Faults

Faults are fractures in the Earth's crust where blocks of rock move relative to each other. Understanding different types of faults—like normal, reverse, and strike-slip—helps explain how tectonic forces shape our planet's landscape and contribute to geological features.

1. Normal fault

   • Occurs when the crust is extended, causing one block of rock to move down relative to another.
   • Typically found in regions experiencing tectonic stretching, such as rift zones.
   • The hanging wall moves downward relative to the footwall.
   • Commonly associated with the formation of valleys and basins.

2. Reverse fault

   • Formed when the crust is compressed, causing one block of rock to move up relative to another.
   • The hanging wall moves upward relative to the footwall.
   • Often found in convergent plate boundaries where tectonic plates collide.
   • Can create mountain ranges and uplifted terrains.

3. Strike-slip fault

   • Characterized by horizontal movement of rock blocks past each other.
   • The movement is primarily lateral, with little vertical displacement.
   • Commonly associated with transform plate boundaries.
   • Can result in features like offset rivers and roads.

4. Thrust fault

   • A type of reverse fault with a low-angle fault plane.
   • The hanging wall is pushed up over the footwall due to compressional forces.
   • Often found in mountain ranges and areas of significant tectonic activity.
   • Can lead to the stacking of rock layers, creating complex geological structures.

5. Oblique-slip fault

   • Exhibits both vertical and horizontal movement, combining features of normal and strike-slip faults.
   • The movement can be a result of complex tectonic forces acting on the crust.
   • Common in regions where multiple stress regimes are present.
   • Can create varied geological features due to its mixed movement.

6. Transform fault

   • A specific type of strike-slip fault that occurs at plate boundaries.
   • Characterized by the lateral sliding of tectonic plates past one another.
   • Often associated with significant seismic activity and earthquakes.
   • Examples include the San Andreas Fault in California.

7. Listric fault

   • A curved fault that flattens with depth, often associated with normal faulting.
   • The hanging wall moves downwards along a curved surface.
   • Common in extensional tectonic settings, such as rift zones.
   • Can lead to the formation of large-scale geological structures like half-grabens.

8. Horst and graben

   • Horsts are elevated blocks of the Earth's crust, while grabens are down-dropped blocks.
   • Formed through extensional tectonics, often associated with normal faulting.
   • Commonly found in rift valleys and areas of crustal stretching.
   • The alternating pattern of horsts and grabens creates distinct topographical features.