Overview
This lecture discusses the processes and resulting landforms along divergent and transform plate boundaries, explaining plate tectonic movements and features formed at these boundaries.
Plate Tectonics Basics
- The Earth's lithosphere is broken into tectonic plates that move over the asthenosphere.
- Plate boundaries are classified as convergent, divergent, or transform, based on relative motion.
Divergent Plate Boundaries
- Divergent boundaries occur where tectonic plates move away from each other.
- Most divergent boundaries are found along mid-ocean ridges, where new oceanic crust forms.
- Magma rises to fill the gap at divergent boundaries, creating new crust as it cools.
- Seafloor spreading is the process where new oceanic crust forms and slowly moves away from the ridge.
- Rift valleys are formed on land when continental plates diverge.
Landforms at Divergent Boundaries
- Mid-ocean ridges are underwater mountain ranges formed by upwelling magma at oceanic divergent boundaries.
- Rift valleys, like the East African Rift, form on continents where plates move apart.
- New ocean basins may eventually form if rifting continues over time.
Transform Plate Boundaries
- Transform boundaries occur where plates slide past each other horizontally.
- No new crust is created or destroyed at transform boundaries.
- Movements along transform faults can cause earthquakes due to the build-up and sudden release of stress.
Landforms at Transform Boundaries
- Fault lines, such as the San Andreas Fault in California, are characteristic features of transform boundaries.
- Linear valleys and offset landforms can occur where transform faults break the Earth's surface.
Key Terms & Definitions
- Lithosphere — rigid outer layer of Earth, divided into tectonic plates.
- Asthenosphere — partially molten layer beneath the lithosphere, enabling plate motion.
- Divergent Plate Boundary — area where plates move apart, forming new crust.
- Seafloor Spreading — creation of new oceanic crust at mid-ocean ridges.
- Transform Plate Boundary — area where plates slide past each other horizontally.
- Fault — fracture in Earth's crust where movement has occurred.
- Rift Valley — lowland region formed by the divergence of tectonic plates.
Action Items / Next Steps
- Review map examples of divergent and transform boundaries.
- Prepare for a quiz on types of plate boundaries and associated landforms.