Earth Science: Types of Plate Boundaries

Study Notes

Types of Plate Boundaries

Convergent Boundaries
- Plates move towards each other.
- Can form mountains or cause subduction (one plate going beneath another).
- Associated with earthquakes and volcanic activity.
Divergent Boundaries
- Plates move apart from each other.
- Typically found at mid-ocean ridges.
- New crust is created as magma rises to the surface.
Transform Boundaries
- Plates slide past one another horizontally.
- Characterized by strike-slip faults.
- Often lead to earthquakes (e.g., San Andreas Fault).

Continental Drift

Proposed by Alfred Wegener in the early 20th century.
Theory that continents were once connected (Pangaea) and have drifted apart over time.
Evidence includes:
- Fossil correlations across continents.
- Similar rock formations and geological features.
- Fit of continental margins.

Plate Movement Mechanisms

Mantle Convection
- Heat from the Earth’s core causes convection currents in the mantle.
- Drives the movement of tectonic plates.
Ridge Push
- Newly formed crust at mid-ocean ridges is elevated, pushing plates away from the ridge.
Slab Pull
- The subduction of a plate (oceanic) pulls the rest of the plate down into the mantle.

Seafloor Spreading

Process where new oceanic crust is formed at mid-ocean ridges.
Involves the upward movement of magma, which creates new crust as it cools.
Evidence includes:
- Age of oceanic rocks (younger near ridges).
- Magnetic striping on the ocean floor showing reversals in Earth’s magnetic field.
- Symmetrical patterns of rock ages on either side of mid-ocean ridges.

Types of Plate Boundaries

Convergent Boundaries: Plates converge, leading to mountain formation or subduction, causing geological features like trenches and volcanic arcs.
Divergent Boundaries: Plates diverge, commonly located at mid-ocean ridges, where new crust is generated through rising magma.
Transform Boundaries: Plates slide past each other horizontally, resulting in strike-slip faults and frequent earthquakes, exemplified by the San Andreas Fault.

Continental Drift

Introduced by Alfred Wegener, this theory posits that continents were once joined as Pangaea, subsequently drifting apart.
Evidence supporting the theory includes:
- Fossil correlations across present-day separate continents.
- Geological similarities, such as rock formations.
- The fit of continental margins, suggesting they were once connected.

Plate Movement Mechanisms

Mantle Convection: Heat from the Earth's core generates convection currents in the mantle, which contribute to tectonic plate movement.
Ridge Push: Elevated newly formed crust at mid-ocean ridges causes plates to move away from the ridge due to gravitational forces.
Slab Pull: The process of subduction pulls the rest of the oceanic plate down into the mantle, facilitating plate movement.

Seafloor Spreading

A process that generates new oceanic crust at mid-ocean ridges through the upward movement of magma and its subsequent cooling.
Key evidence includes:
- Younger oceanic rocks found closer to ridges.
- Magnetic striping on the ocean floor that indicates historical magnetic field reversals.
- Symmetrical age patterns of rocks created on either side of mid-ocean ridges, affirming the theory of seafloor spreading.

Description

This quiz explores the three main types of plate boundaries: convergent, divergent, and transform. It also covers the theory of continental drift proposed by Alfred Wegener, including evidence supporting this geological concept. Test your knowledge on the mechanisms of plate movement and their implications for Earth’s geology.