How mountain ranges are formed at convergent plate boundaries

Summary

This video script explores the geological processes at a convergent plate boundary where continental plates collide. Unlike subduction involving oceanic plates, continental plates, being lighter, resist sinking into the asthenosphere. The collision results in the formation of high mountain ranges, known as orogenic belts, and crust thickening up to 80 km. The script highlights the absence of volcanoes due to the lack of subduction and references the Alpine orogeny, a period that shaped the Alps and Himalayas about 60 million years ago.

Takeaways

• 🌏 At a convergent plate boundary, when an oceanic plate subducts beneath a continental plate, the continental crust can also be affected by the subduction process.
• 🏞️ When two continental plates collide, there is little to no subduction due to their buoyancy relative to the asthenosphere, leading to compression and mountain formation.
• 📏 The collision of continental plates results in the creation of high mountain ranges known as orogenic belts, such as the Alps and the Himalayas.
• 🌌 The crust beneath mountain ranges becomes significantly thicker, reaching up to about 80 kilometers, due to the buoyant nature of the crust on the asthenosphere.
• 🌋 Unlike convergent boundaries with oceanic plates, there are no volcanoes at continental convergent boundaries because of the lack of subduction.
• 🚨 Earthquakes are common at these plate boundaries due to the tectonic activity, but the absence of subduction means volcanic activity is absent.
• 🕰️ The African and Indian plates' northward movement against the Eurasian plate started about 60 million years ago, leading to the formation of many mountain ranges during the Alpine orogeny.
• 🏔️ The term 'Alpine orogeny' refers to the geological period when the mountain ranges from Morocco to India were formed.
• 🗻 Mountain ranges can be eroded and worn down over time, with some, like the Ardennes, being completely eroded and others disappearing entirely.
• 🏞️ There have been previous periods of mountain formation, such as those that created the Ardennes and the Scottish Highlands, before the Alpine orogeny.
• 🔍 The script emphasizes the geological processes and history behind the formation of mountain ranges at continental convergent plate boundaries.

Q & A

What occurs when two continental plates collide at a convergent plate boundary?

When two continental plates collide, there is little or no subduction due to both plates being lighter than the underlying asthenosphere. Instead, the plates are pushed together, causing compression and the formation of high mountain ranges known as orogenic belts.

How are mountain ranges formed during the collision of continental plates?

Mountain ranges are formed by the folding and compression of the crust as the continental plates push against each other. This process thickens the crust, particularly beneath the mountain range, which can reach up to about 80 kilometers in thickness.

What is the term used to describe the geological process of mountain formation during the collision of continental plates?

The term used for the geological process of mountain formation during the collision of continental plates is 'orogeny'. In the context of the script, the specific period of mountain formation is referred to as the Alpine orogeny.

What is the difference between a mountain range formed at a convergent boundary involving continental plates and one involving an oceanic plate?

A mountain range formed at a convergent boundary involving continental plates does not have associated volcanoes due to the lack of subduction. In contrast, a convergent boundary involving an oceanic plate typically has subduction, leading to volcanic activity.

Why are there no volcanoes at a convergent plate boundary where only continental plates are involved?

There are no volcanoes at a convergent plate boundary where only continental plates are involved because subduction, which is the process that leads to volcanic activity as the oceanic plate melts, does not occur when two continental plates collide.

What is the term 'asthenosphere' in the context of plate tectonics?

The asthenosphere is a part of the Earth's mantle that lies below the lithosphere. It is more fluid and ductile, allowing tectonic plates to move over it. The buoyancy of continental plates on the asthenosphere prevents significant subduction during continental collisions.

How are the African plate and the Indian plate related to the formation of the Himalayas?

The African plate and the Indian plate moved north against the Eurasian plate. This convergent movement, which started about 60 million years ago, led to the formation of many mountain ranges, including the Himalayas, as part of the Alpine orogeny.

What is the significance of the term 'Alpine orogeny' in the context of the script?

The term 'Alpine orogeny' refers to the specific geological period during which the mountain ranges from Morocco to India, including the Alps and the Himalayas, were formed due to the northward movement of the African and Indian plates against the Eurasian plate.

How do erosion and weathering affect the longevity of mountain ranges?

Erosion and weathering can significantly reduce the height of mountain ranges over time. For example, the Ardennes were completely worn down, and other mountain ranges have disappeared completely due to these natural processes.

What is the role of the slab pull in the subduction process?

The slab pull is the force exerted by the weight of the subducting plate, which pulls the rest of the plate towards the subduction zone. This force contributes to the movement of the plate and the cooling of the plate as it is drawn into the subduction zone.

Can you provide an example of a mountain range that was formed during an earlier orogeny and has since been eroded?

The Ardennes and the Scottish Highlands are examples of mountain ranges that were formed during earlier periods of orogeny but have since been significantly eroded and worn down.