RAS question
The San Andreas Fault in California is an example of which type of plate boundary?
Correct answer: (D) Transform boundary.
The San Andreas Fault in California is a transform plate boundary where the Pacific Plate and the North American Plate slide horizontally past each other.
Explanation
The San Andreas Fault is a classic transform boundary, not a spreading or collision zone. USGS defines a transform boundary as a plate boundary where crust is neither created nor destroyed because the plates slide horizontally past one another. USGS also identifies the San Andreas fault zone in California as one of the few transform faults exposed on land. In this case, the Pacific Plate and the North American Plate move laterally past each other, which explains why the fault is associated with frequent earthquake activity rather than volcanic ridge formation or subduction. The fault is about 1,200 km long and is responsible for many earthquakes in California.
Why the other options are wrong
- (A) A divergent boundary is where plates move apart and new crust is generated, while the San Andreas Fault involves horizontal sliding between plates.
- (B) A hotspot is not a plate-boundary type; the San Andreas Fault is described as a transform fault between two moving plates.
- (C) A convergent boundary involves plates moving towards each other, often with crust being destroyed by subduction, but the San Andreas is a lateral sliding boundary.
Concept
This tests the plate-boundary types in World Geography, especially the difference between divergent, convergent and transform margins. It recurs in RAS because earthquakes, faults and tectonic landforms are core physical-geography themes.