The Wilson Cycle and Plate Boundaries

Summary

This video explains the Wilson Cycle, a model for the formation and destruction of supercontinents. Starting with the breakup of Pangea, the cycle involves several stages: rifting, the opening of new ocean basins, and eventual subduction that leads to the formation of a new supercontinent. It discusses active and passive rifting mechanisms, the juvenile and mature stages of ocean basin formation, and the process of subduction. The video concludes by describing the collision of continental plates, forming mountain ranges like the Himalayas, and highlights the power of geological processes that shape Earth’s surface.

Takeaways

• 😀 The Wilson Cycle, named after J. Tuzo Wilson, explains the formation and destruction of supercontinents through stages of rifting, ocean basin formation, and subduction.
• 😀 The cycle begins with the embryonic stage, where the supercontinent (e.g., Pangea) starts to experience rifting, eventually leading to the breaking apart of landmasses.
• 😀 Rifting can be either active (driven by mantle plumes) or passive (caused by tensional forces), leading to the formation of normal faults and fissure volcanoes.
• 😀 A triple junction is formed during rifting, where three tectonic plates separate, and this process can be seen in places like the Red Sea and East African Rift.
• 😀 In the juvenile stage, the rift valley widens, eventually connecting to the ocean, creating new oceanic crust and forming divergent plate boundaries, like the Red Sea.
• 😀 The mature stage is characterized by a vast ocean basin, such as the Atlantic Ocean, which continues to grow today at the mid-Atlantic ridge.
• 😀 The declining stage marks the beginning of ocean basin closure as subduction starts, with oceanic lithosphere sinking back into the mantle.
• 😀 Subduction occurs when oceanic lithosphere becomes cold and dense after it moves away from the mid-ocean ridge, and typically starts after the lithosphere is around 200 million years old.
• 😀 Convergent plate boundaries, where subduction occurs, can be ocean-ocean (forming volcanic island arcs) or ocean-continental (forming continental arcs like the Cascade Range).
• 😀 The final stage of the Wilson Cycle involves the suturing of rifted supercontinent fragments, forming a new supercontinent and dramatic mountain ranges, such as the Himalayas, through continent-continent collision.

Q & A

What is the Wilson Cycle?

The Wilson Cycle is a geological model that explains the formation and destruction of supercontinents. It describes the processes of continental rifting, ocean basin formation, subduction, and the eventual reformation of supercontinents.

Who is the Wilson Cycle named after?

The Wilson Cycle is named after J. Tuzo Wilson, a Canadian geologist who proposed the model to describe the life cycle of supercontinents.

What are the two main types of rifting in the Wilson Cycle?

The two main types of rifting are active rifting, which is driven by mantle plumes, and passive rifting, which is caused by external forces such as gravitational or tectonic stresses.

How does active rifting occur?

Active rifting occurs when a mantle plume beneath a supercontinent causes the lithosphere to heat up, stretch, and eventually break apart. This often results in the formation of a triple junction where three tectonic plates meet.

What is the role of passive rifting in the Wilson Cycle?

In passive rifting, external forces, like tectonic or gravitational stresses, cause the lithosphere to extend and thin. This leads to the formation of a mantle plume and eventually initiates the breakup of a continent.

What is a triple junction, and why is it important in the Wilson Cycle?

A triple junction is a point where three tectonic plates meet. It plays a crucial role in rifting, as continents often break apart along triple junctions, leading to the formation of new tectonic plates.

What are examples of modern-day locations in the juvenile stage of the Wilson Cycle?

The Red Sea and the Sea of Cortés are modern examples of regions in the juvenile stage, where rifting has led to the creation of new oceanic crust and widening ocean basins.

What happens during the mature stage of the Wilson Cycle?

During the mature stage, the ocean basin continues to expand as new oceanic crust is formed at mid-ocean ridges. This stage is characterized by a well-established ocean basin, such as the Atlantic Ocean.

How does subduction contribute to the closing of ocean basins in the Wilson Cycle?

Subduction occurs when older, cooler oceanic lithosphere becomes dense enough to sink into the mantle. This process begins the closure of ocean basins as oceanic crust is consumed and pushed back into the Earth.

What geological features are formed at convergent boundaries during subduction?

At convergent boundaries, subduction can form volcanic island arcs (ocean-ocean subduction) or continental arcs (ocean-continental subduction), as well as deep ocean trenches.

What is the final stage of the Wilson Cycle, and what does it lead to?

The final stage is the suturing stage, where tectonic plates collide and fuse to form a new supercontinent. This stage results in the creation of mountain ranges and the reset of the Wilson Cycle.