Overview
This lecture covers the types of plate boundaries and the geological processes and landforms formed at convergent, divergent, and transform boundaries, including key safety tips during earthquakes.
Types of Plate Boundaries
- The three types of plate boundaries are convergent, divergent, and transform fault boundaries.
- Plate tectonics explains the movement of Earth's lithosphere (crust and upper mantle) causing geological processes and landform creation.
Convergent Plate Boundaries
- Convergence can occur between oceanic & continental plates, two oceanic plates, or two continental plates.
- When oceanic and continental plates converge, the denser oceanic plate subducts beneath the continental plate, forming trenches, mountains, volcanoes, and earthquakes.
- The subducted plate melts into magma, leading to volcanic activity.
- When two oceanic plates converge, the older, denser plate subducts, resulting in deep earthquakes, tsunamis, oceanic trenches, volcanic island arcs, and loss of oceanic lithosphere.
- When two continental plates converge, neither subducts due to equal density, causing shallow earthquakes, fault formation, and the creation of mountain ranges (e.g., Sierra Madre).
- Subduction and volcanic activity do not occur in continental-continental convergence.
Divergent Plate Boundaries
- At divergent boundaries, plates move away from each other due to rising convection currents.
- Divergence forms rift valleys on land and oceanic ridges underwater.
- New crust forms as mantle material rises and cools in the gap between the plates.
Transform Fault Boundaries
- Plates at transform boundaries slide past each other horizontally, resulting in fault lines.
- The movement can cause strong earthquakes but does not create volcanoes or mountains.
- Earthquake preparedness includes following "Duck, Cover, and Hold" procedures.
Earthquake Safety & Preparedness
- During ground shaking, kneel on one knee ("duck") for quick evacuation.
- Protect the head as it is most vulnerable during earthquakes.
- Evacuation centers provide support for disaster victims.
Key Terms & Definitions
- Convergent Boundary — where two plates move toward each other, often causing subduction or mountain formation.
- Subduction — process where one plate moves under another and sinks into the mantle.
- Divergent Boundary — where two plates move apart, creating new crust.
- Transform Fault Boundary — where two plates slide horizontally past each other.
- Rift Valley — a valley formed by the divergence of two plates on land.
- Oceanic Ridge — underwater mountain range formed at divergent boundaries.
- Fault — a crack in the Earth's crust due to plate movement.
- Magma — molten rock beneath the Earth's surface.
Action Items / Next Steps
- Complete simulation activities in Module 3, pages 5-7 and 12.
- Answer questions 7, 8, 9, 14, 15, and 16 in the module as discussed.
- Review earthquake safety procedures ("Duck, Cover, and Hold").