Transform Fault Boundaries

Andrea Murphy, Mary Ellen Ellis
  • Author
    Andrea Murphy

    Andrea Murphy has extensive experience working as a research associate for Midwestern University in the fields of molecular cell biology, genetics, and microbiology. She has also taught high school biology and has experience teaching at the graduate level laboratory assays and techniques. Andrea has a Master's degree in Biomedical Sciences from Midwestern University, Bachelor's degree in Biomedical science from Midwestern University, and an associates degree of Arts and Science.

  • Instructor
    Mary Ellen Ellis

    Mary Ellen is a science and education writer with a background in chemistry. She holds an M.S. in analytical chemistry and has worked as a high school science teacher.

Learn about the transform fault and understand how and where it forms. Explore the plate boundary definition, and read about types and examples of transform faults. Updated: 05/22/2022

Table of Contents


What is a Transform Fault?

Rather than a break in the Earth's crust, a fault is a distortion in the crust caused by the movement of tectonic plates. It allows the rocks to move relative to each other. A transform fault is a specific type of strike-slip fault identified by a horizontal break in the rock connecting two tectonic plates. Similar to a transform boundary, a transform fault is located where the blocks of rocks scrape past each other horizontally, connecting tectonic plates. They are considered to be conservative boundaries because the crust of the Earth is not created or destroyed. Transform faults may be as small as a few millimeters in length or can be as large as thousands of kilometers. It can connect mid-ocean ridges and other plate boundaries, making a zig-zag pattern.

Transform fault shown in red. Transform fault formed by two tectonic plates moving in opposite directions.

Image shows transform faults formed by tectonic plate moving in opposite directions.

Plate Boundaries

The thin layer that covers the Earth is called the crust. The Earth's crust is not one solid piece; it is broken into several parts known as tectonic plates. A boundary is where tectonic plates meet. These tectonic plates are in constant movement, and their motion relative to each other determines the activity found at that boundary and identifies the type of boundary. A boundary between tectonic plates can be convergent, divergent, or transform.

  • Convergent plant boundaries are when two tectonic plates collide, destroying the existing crust. These boundaries cause earthquakes, ocean trenches, and formations of mountains or volcanoes.
  • Divergent boundaries are when the tectonic plates diverge apart. As the plates separate, magma rises from the mantle of the Earth, cools, and solidifies, creating a new crust. These boundaries form earthquakes, midocean ridges, rift valleys, and volcanos.

Image showing the three types of plate boundaries above. It is a cross-section of the Earth showing the mantle

Transform Boundary

A transform boundary is area where the two plates scrape past each other horizontally, and no crust is created and destroyed, making it a conservative boundary. The movement at transform boundaries will cause intense earthquakes and provide a geologic record of the Earth's crust. A transform fault will form between tectonic plates where each plate moves away from the divergent plate boundary.

The earthquakes that occur at boundaries cause stress through the crust of the Earth; rocks at the surface will break in response to the stress-forming faults. Transform boundaries are considered faults, but not all faults are plate boundaries as they can be found throughout the tectonic plate, away from the plate boundary. In a thicker crust, faults can be created by the rise and fall of hot magma in the Earth's mantle, causing the overlying crust to expand. The expansion of the crust can cause cracks and movement in the rock, creating a fault line.

Formation of transform faults on a continental tectonic plate away from a plate boundary.

Image of tectonic plate stretching and thinning forming a rift valley and transform fault lines.

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Types of Transform Faults

There are two distinct types of crust on Earth: oceanic and continental. Oceanic crust is denser and thinner than continental crust and is found under the oceans. Continental crust is thicker and is present under the continents. If a transform fault is located on the oceanic crust, then it is an oceanic transform fault. If the transform fault line is located on the continental crust, then it is a continental transform fault. Transform faults can be found on both continental and oceanic crusts together, but both plates should move away from a divergent boundary.

Oceanic Transform Faults

Beneath the ocean, new crust is created at divergent boundaries. As the plates pull away from each other, the hot magma from the mantle rises to fill the space between the plates. The magma cools and solidifies, forming a new oceanic crust. At these divergent boundaries, mid-ocean ridges are formed from the plates being pulled apart. A mid-ocean ridge is a mountain range that rises from the ocean floor. The largest mid-ocean ridge is the Mid-Atlantic Ridge extending from the Arctic, running down the middle of the Atlantic Ocean down past the tip of Africa.

The Mid-Atlantic Ridge

Image of the Mid-Atlantic Ridge travel down the middle of the Atlantic ocean, expanding from the Artic past the tip of Africa.

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Frequently Asked Questions

What is an example of a transform fault?

A transform fault is a strike-slip fault that connects two tectonic plates moving in opposite directions away from a divergent boundary. Examples include San Andres Fault, Alpine Fault, and North Anatolian Fault.

What happens in a transform fault?

A transform fault is formed by two tectonic plates moving horizontally in opposite directions away from a divergent boundary. There is a lot of friction between the plates as they move against each other. Since the crust is rough, it will get stuck and build up pressure. Once the pressure becomes too great, the energy will be released, resulting in an earthquake.

What are two types of transform faults?

There are two types of transform faults; those located in the oceanic crust connecting mid-ocean ridges are known as oceanic transform faults. Transform faults found in the continental crust are called continental transform faults.

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