Overview
This lecture discusses transform plate boundaries, explaining their characteristics, associated hazards, and major examples like the San Andreas Fault, while comparing them to other types of plate boundaries.
Characteristics of Transform Boundaries
- Transform boundaries involve two tectonic plates sliding past each other horizontally.
- Unlike divergent (pulling apart) or convergent (colliding) boundaries, no crust is created or destroyed at transform boundaries.
- These boundaries do not produce volcanoes.
- Most transform boundaries are found along mid-ocean ridges, adjusting for differences in the spreading rates of neighboring segments.
Hazards of Transform Boundaries
- Transform boundaries are sites of moderate to large earthquakes due to irregular movement and pressure buildup.
- Earthquakes occur when locked sections of the boundary suddenly slip and release accumulated energy.
- Areas with locked transform boundaries, such as parts of the San Andreas Fault, are at higher risk for large earthquakes.
The San Andreas Fault
- The San Andreas Fault is a well-known transform boundary between the North American and Pacific plates in California.
- Major cities like San Francisco and Los Angeles are located near locked segments of this fault, making them vulnerable to earthquakes.
- The fault does not produce mountains or volcanoes but causes visible displacement of landscape features across the boundary.
Plate Boundary Summary
- Divergent boundaries: plates move apart, creating new crust and often forming mid-ocean ridges.
- Convergent boundaries: plates move together, resulting in crust destruction or mountain formation.
- Transform boundaries: plates slide past one another, only displacing features and causing earthquakes.
Key Terms & Definitions
- Transform Boundary — a plate boundary where two tectonic plates slide past each other horizontally.
- Earthquake — sudden ground movement caused by the release of pressure when plates slip along a fault.
- Locked Segment — a section of a fault where plates are stuck and pressure builds until released by an earthquake.
- Creeping Segment — a section of a fault where plates move smoothly with little pressure buildup.
- Mid-Ocean Ridge — an underwater mountain range at a divergent boundary where new oceanic crust forms.
Action Items / Next Steps
- Review the three types of plate boundaries and their distinguishing features.
- Study examples of transform boundaries, especially the San Andreas Fault.
- Prepare for questions comparing hazards and features of each boundary type.