Transform Boundary: Definition, Facts & Examples

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  • 0:03 What is a Transform Boundary?
  • 0:42 Features of Transform…
  • 2:06 Examples of Transform…
  • 3:06 Lesson Summary
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Lesson Transcript
Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

In this lesson, you will learn the meaning of the term 'transform boundary' in the context of plate tectonics. A number of features and examples of transform boundaries will be introduced. A short quiz will follow.

What is a Transform Boundary?

The Earth is like a pool covered with floats of different sizes and shapes that we call tectonic plates. Although it seems like the Earth's crust is huge and immovable, the ground is actually moving all the time as it floats on a sea of hot magma. And just like with a pool, the floats sometimes randomly hit each other. They can move towards each other, move away from each other, and slide alongside each other. A transform boundary (or conservative boundary) is where two of the tectonic plates slide alongside each other. When this happens, the scraping of the two plates causes earthquakes.

Features of Transform Boundaries

Unlike divergent and convergent boundaries, at transform boundaries no new crust is created, and there is no subduction (or sandwiching) of plates. This makes the features of transform boundaries decidedly less exciting. However, the effects from a human perspective can still be quite dramatic. At transform boundaries, where plates slide past each other, you might observe linear valleys where rock has been ground down to leave gaps, or river beds that have been broken into two because the two halves have shifted in opposite directions.

Very rarely, it is possible for magma to reach the surface due to the intense temperatures and pressures associated with all tectonic plate boundaries, but this isn't the norm. Rather, transform boundaries are characterized by some of the most intense earthquakes in the world. Transform faults can also develop on a smaller scale where pieces of seafloor spread apart. This can form a zigzag break, where some edges are moving apart and others are sliding alongside, as in this diagram.

Zigzag breaks can form along transform boundaries
Diagram of zigzag break

In 1906, a huge earthquake hit San Francisco due to the nearby transform boundary. A lot of buildings were destroyed by the earthquake itself, but those that survived didn't last long in the widespread fires that followed. At least 600 people died in the earthquake and aftermath.

Examples of Transform Boundaries

The most famous transform boundary is probably the San Andreas Fault in California. People often say that California will one day fall off into the ocean. But, is that really true?

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