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## 17.3 Notes: Plate Boundaries ### Theory of Plate Tectonics - Plate tectonics is the theory that Earth's lithosphere is broken up into pieces that are moving slowly over Earth's surface. - Each large piece of lithosphere is called a tectonic plate. Scientists have identified 7 major plates and nu...

## 17.3 Notes: Plate Boundaries ### Theory of Plate Tectonics - Plate tectonics is the theory that Earth's lithosphere is broken up into pieces that are moving slowly over Earth's surface. - Each large piece of lithosphere is called a tectonic plate. Scientists have identified 7 major plates and numerous smaller plates on Earth. - Plates move in different directions and at different rates relative to one another, and they interact with each other at their boundaries. ### Types of Boundaries - **Divergent Boundaries** - Occur when 2 tectonic plates are moving apart - Most divergent boundaries are found on the seafloor (think Mid-Atlantic Ridge).