* Plate Tectonics: The Earth's outer layer (the lithosphere) is broken into giant pieces called tectonic plates. These plates are constantly moving, driven by heat from the Earth's core.
* Plate Boundaries: The edges where plates meet are called plate boundaries. There are three main types:
* Divergent Boundaries: Plates move apart, creating new crust (like the mid-Atlantic ridge).
* Convergent Boundaries: Plates collide, causing one plate to subduct (slide) under the other (like the Andes Mountains).
* Transform Boundaries: Plates slide past each other horizontally (like the San Andreas Fault).
Why Earthquakes Happen at Boundaries:
* Stress and Strain: The movement of plates at boundaries creates enormous stress and strain on the rocks.
* Faulting: When the stress exceeds the strength of the rocks, they break along fractures called faults.
* Seismic Waves: The sudden release of energy along a fault sends out vibrations called seismic waves that we feel as earthquakes.
Specific Examples:
* Divergent Boundaries: Earthquakes at divergent boundaries are generally smaller and shallower. The new crust forming releases stress gradually.
* Convergent Boundaries: These boundaries generate the most powerful earthquakes. The collision forces cause massive stress and can trigger deep, destructive quakes.
* Transform Boundaries: Earthquakes along transform boundaries are often shallow but can be very strong. The horizontal sliding motion can cause significant ground shaking.
In summary: Plate boundaries are zones of intense geological activity. The constant movement and interaction of plates create the forces that lead to earthquakes.
