Plate Tectonic Boundaries: Divergent Boundaries // LACC 274

Summary

The video explains divergent boundaries, where tectonic plates move apart, exemplified by the Mid-Atlantic Ridge. This movement creates low-pressure areas that lead to magma formation through decompression melting, resulting in sea floor spreading and the creation of new ocean floor. The Great Rift Valley in East Africa serves as another example, showcasing how mantle convection causes rifting and the formation of valleys and horsts. The process is associated with earthquake activity and some volcanic phenomena, providing insight into the dynamic nature of Earth's geology.

Takeaways

• 🌍 Divergent boundaries occur where tectonic plates are pulling apart, such as at the Mid-Atlantic Ridge.
• 🌊 Sea floor spreading is the process that creates new ocean floor as magma rises and solidifies.
• 🔥 Decompression melting is the formation of magma due to low pressure as plates diverge.
• ⚖️ Gravity plays a significant role in moving plates, especially as one subducts into the mantle.
• 🔄 Convection currents in the mantle contribute to the movement of tectonic plates, similar to a lava lamp's flow.
• 🏞️ The Great Rift Valley in East Africa is a land-based example of divergent boundaries, where the continental crust is being pulled apart.
• 📉 As plates diverge, the central area can fall, forming rift valleys or grabens.
• ⛰️ The raised blocks of crust adjacent to rift valleys are called horsts.
• 💥 Earthquakes are common in divergent boundaries due to the movement and cracking of tectonic plates.
• 🌋 Minor volcanic activity can occur in these regions as magma seeps through cracks, although it is not typically explosive.

Q & A

What are divergent boundaries?

Divergent boundaries are tectonic plate boundaries where two ocean plates are pulling apart from each other.

What is decompression melting?

Decompression melting is a process that occurs at divergent boundaries where the reduction in pressure allows magma to form due to the movement of tectonic plates.

How does magma form at the Mid-Atlantic Ridge?

At the Mid-Atlantic Ridge, magma forms due to low pressure as the ocean plates diverge, leading to decompression melting.

What is sea floor spreading?

Sea floor spreading is the process where new ocean floor is created as magma rises and solidifies at divergent boundaries.

What forces cause tectonic plates to move apart?

The movement of tectonic plates apart is influenced by gravity acting on subducting plates and convection currents in the mantle.

What is the Great Rift Valley, and why is it significant?

The Great Rift Valley in East Africa is an area where the continental plate is diverging, which could eventually lead to it breaking off from the rest of the continent.

How do temperature variations in the mantle affect tectonic plate movement?

Hot areas of the mantle rise because they are less dense, while cooler areas sink. This movement creates convection currents that exert pressure on tectonic plates, causing them to diverge.

What is a rift, and how does it form?

A rift is a valley that forms in the center of a divergent boundary due to the downward movement of the crust as the plates pull apart.

What are the terms 'graben' and 'horst' in the context of rift valleys?

In rift valleys, a 'graben' refers to the lower part that has fallen down, while 'horst' refers to the elevated areas or shoulders of the rocks.

What types of volcanic activity are associated with divergent boundaries?

Divergent boundaries typically exhibit non-explosive volcanic activity, where magma seeps through cracks rather than resulting in explosive eruptions.