Plate Boundaries: Transform
We're almost done with the topic 'Plate boundaries'. We are on the third and the last main type of plate boundaries, the Transform boundaries. Again for this topic, I will remind you that PLATE BOUNDARIES ARE ALWAYS FAULTS, BUT NOT ALL FAULTS ARE PLATE BOUNDARIES. So let's know what Transform Plate Boundaries are.
Transform Plate Boundary
Transform boundaries
Transform boundaries are places where plates slide sideways past each other. At transform boundaries lithosphere is neither created nor destroyed. Many transform boundaries are found on the sea floor, where they connect segments of diverging mid-ocean ridges. California's San Andreas fault is a transform boundary. [1] Transform Plate Boundaries are locations where two plates slide past one another. The fracture zone that forms a transform plate boundary is known as a transform fault. Most transform faults are found in the ocean basin and connect offsets in the mid-ocean ridges. A smaller number connect mid-ocean ridges and subduction zones. [2]
It is a type of fault whose relative motion is predominantly horizontal, in either a sinistral (left lateral) or dextral (right lateral) direction. Furthermore, transform faults end abruptly and are connected on both ends to other faults, ridges, or subduction zones.[1] While most transform faults are hidden in the deep oceans where they offset divergent boundaries as series of short zigzags accommodating seafloor spreading, the best-known (and most destructive) are those on land at the margins of tectonic plates. Transform faults are the only type of strike-slip fault that can be classified as a plate boundary. [3]
The Difference between Strike-Slip Fault and Transform Fault
A Strike-Slip Fault is NOT a Transform Fault
Transform faults can be distinguished from the typical strike-slip faults because the sense of movement is in the opposite direction (see illustration above). A strike-slip fault is a simple offset; however, a transform fault is formed between two different plates, each moving away from the spreading center of a divergent plate boundary. When you look at the transform fault diagram, imagine the double line as a divergent plate boundary and visualize which way the diverging plates would be moving. [2]
San Andreas movie poster
Have you heard of the movie San Andreas? It is a 2015 movie where in the aftermath of a massive earthquake in California, a rescue-chopper pilot, played by Dwayne Johnson, makes a dangerous journey with his ex-wife across the state in order to rescue his daughter. [4] It is the vision of the great movement of the San Andreas Fault, which is a transform plate boundary.
San Andreas fault
The San Andreas Fault is the transform boundary between the North American Plate and the Pacific Plate. During the 1906 San Francisco earthquake the northern section of the San Andreas Fault slipped northward along the fault from San Juan Bautista to Cape Mendocino, a total of 296 miles (477km). [5] The San Andreas fault zone, which is about 1,300 km long and in places tens of kilometers wide, slices through two thirds of the length of California. Along it, the Pacific Plate has been grinding horizontally past the North American Plate for 10 million years, at an average rate of about 5 cm/yr. Land on the west side of the fault zone (on the Pacific Plate) is moving in a northwesterly direction relative to the land on the east side of the fault zone (on the North American Plate). [6]
We're done with the three main types of plate boundaries but there is still one more type which is the Plate-boundary zones.
Plate-boundary zones
Plate boundary zones are the zones of interaction between adjacent plates where they collide, pull apart or slide past each other. These zones may be anything from a few kilometres to a few hundred kilometres wide. [7] Not all plate boundaries are as simple as the main types discussed above. In some regions, the boundaries are not well defined because the plate-movement deformation occurring there extends over a broad belt (called a plate-boundary zone). One of these zones marks the Mediterranean-Alpine region between the Eurasian and African Plates, within which several smaller fragments of plates (microplates) have been recognized. Because plate-boundary zones involve at least two large plates and one or more microplates caught up between them, they tend to have complicated geological structures and earthquake patterns. [6]
Plate-boundary zones can be the union of the three main types of plate boundaries for it is the zone where large area is covered so the three main types can occur simultaneously.
References:
[1] http://www.geo.cornell.edu/hawaii/220/PRI/PRI_PT_transform.html [2] http://geology.com/nsta/transform-plate-boundaries.shtml [3] https://en.wikipedia.org/wiki/Transform_fault [4] http://www.imdb.com/title/tt2126355/ [5] http://www.kids-fun-science.com/transform-boundary.html [6] https://pubs.usgs.gov/gip/dynamic/understanding.html [7] https://www.gns.cri.nz/Home/Our-Science/Earth-Science/Plate-Tectonics/NZ-plate-boundary
