Overview
This lecture discusses the different types of plate boundaries, the landforms they create, and the geological processes associated with their interactions, with a focus on real-world examples.
Types of Plate Boundaries
- There are three main types of plate boundaries: divergent, convergent, and transform.
- Divergent boundaries occur where plates pull apart, typically creating rift valleys and mid-ocean ridges.
- Convergent boundaries happen where plates collide, resulting in mountain ranges, trenches, and volcanic activity.
- Transform boundaries involve plates sliding past each other, leading to earthquakes but not significant vertical landform changes.
Divergent Plate Boundaries
- At divergent boundaries, plates move apart and magma rises to form new crust.
- Mid-ocean ridges, such as the Mid-Atlantic Ridge, are formed by divergence and are the longest mountain ranges.
- Iceland sits atop a divergent boundary and features many active volcanoes and geothermal activity.
- The East African Rift Valley is a continental example where Africa is splitting apart, creating new rift valleys, volcanoes, and eventually a new ocean basin.
Convergent Plate Boundaries
- Convergent boundaries can be continental-continental, continental-oceanic, or oceanic-oceanic collisions.
- In continental-oceanic collisions, the denser oceanic plate subducts beneath the continental plate, forming trenches and volcanic mountain ranges (e.g., Andes).
- Oceanic-oceanic collisions also involve subduction, forming island arcs (e.g., Japan, Philippines, Aleutian Islands).
- Trenches at these boundaries are the deepest parts of Earth's oceans, like the Mariana Trench.
- Continental-continental collisions do not produce subduction but instead create massive mountain ranges (e.g., Himalayas) with few volcanoes.
Transform Plate Boundaries
- Transform boundaries occur when plates slide horizontally past one another, causing earthquakes (e.g., San Andreas Fault).
Key Terms & Definitions
- Plate Boundary — The region where two tectonic plates meet.
- Divergent Boundary — Area where plates move apart, creating new crust.
- Convergent Boundary — Area where plates move toward each other, causing subduction or mountain building.
- Transform Boundary — Area where plates slide horizontally past each other.
- Subduction — The process of one plate sliding beneath another.
- Mid-Ocean Ridge — An underwater mountain range formed by divergent boundaries.
- Rift Valley — A valley formed by the separation of tectonic plates.
- Trench — A deep depression in the ocean floor at a subduction zone.
- Island Arc — A curved chain of volcanic islands formed above a subducting plate.
Action Items / Next Steps
- Review the different types of plate boundaries and their features.
- Study examples of real-world divergent, convergent, and transform boundaries.
- Prepare for a discussion on hotspots and non-boundary-related volcanism in the next class.