Transform Fault - Examples

Examples

Transform faults are commonly found linking segments of mid-oceanic ridges or spreading centers. These mid-oceanic ridges are where new sea floor is constantly created through the up welling of new basaltic magma. With new sea floor being pushed and pulled out, the older sea floor slowly slides away from the mid-oceanic ridges toward the continents. Although, separated only by tens of kilometers, this separation between the ridges causes the sea floor to be pushed pass each other in opposing directions. This lateral movement of sea floors past each other is where transform faults are currently active.

Transform faults move differently than a strike-slip fault at the mid-oceanic ridge. Instead of the ridges moving away from each other, like other strike-slip faults, transform fault ridges will stay in the same fixed location, and the new ocean sea floor being created at the ridges is pushed away from the ridge. The proof of this is found in paleo-magnetic striping on the sea floor.

A paper written by Gerya theorizes that the creation of the transform faults between the ridges of the mid-oceanic ridge is attributed to rotated and stretched sections of the mid-oceanic ridge. This occurs over long period of time with the spreading center or ridge slowly deforming from a straight line to a curved line and then finally fracturing along these planes forming transform faults. As this takes place, the fault changes from a normal fault with extensional stress to a strike slip fault with lateral stress. In the study done by Bonatti & Crane, peridotite and gabbro rocks were discovered in the edges of the transform ridges. These rocks are created deep inside the Earth’s mantle and then rapidly exhumed to the surface. This evidence helps to prove that new sea floor is being created at the mid-oceanic ridges and further supports the theory of plate tectonics.

As previously stated, active transform faults are between two tectonic structures or faults. Fracture zones represent the previously active transform fault lines, which have since passed the active transform zone and are being pushed toward the continents. These elevated ridges on the ocean floor can be traced for hundreds of miles and in some cases even from one continent across an ocean to the other continent.

The most prominent examples of the mid-oceanic ridge transform zones are located in Atlantic Ocean between South America and Africa. Known as the St. Paul, Romanche, Chain, and Ascension fracture zones, these areas have with deep, easily identifiable transfrom faults and ridges. Other locations include: the East Pacific Ridge located in the South Eastern Pacific Ocean, which meets up with San Andreas Transform fault to the North.

Transform faults are not limited to oceanic crust and spreading centers; many transform faults are located on continental margins. The best example is the San Andreas fault on the Pacific coast of the United States. The San Andreas Fault links the East Pacific Rise off of the West coast of Mexico (Gulf of California) to the Mendocino Triple Junction (Part of the Juan de Fuca plate) located off the coast of the North Western United States making it a ridge-to-transform style transform fault. The formation of the San Andreas Fault system occurred fairly recently during the Oligocene Period between 34 million and 24 million years ago. During this period, the Farallon plate, followed by the Pacific plate, collided into the North American plate. The collision led to the subduction of the Farallon plate underneath the North American plate. Once the spreading center separating the Pacific and Farallon plate was subducted underneath the North American plate, the San Andreas Continental Transform Fault system was created.

Other examples include:

• Middle East's Dead Sea Transform fault
• New Zealand's Alpine Fault
• Pakistan's Chaman Fault
• Turkey's North Anatolian Fault
• North America's Queen Charlotte Fault