BBC Geography - Glaciers

Summary

In this video, we explore the fascinating history of glaciation in the Lake District, England. Over 18,000 years ago, glaciers shaped the region's landscape, carving valleys and creating features like quarries, U-shaped valleys, and hanging valleys. The process of glaciation involved ice movement, erosion, and the collection of debris like scree and erratic stones. As the glaciers melted, they left behind evidence of their immense power, transforming the land into what we see today. The video highlights the powerful forces of nature that shaped the UK's terrain, encouraging viewers to observe the subtle signs of glaciation.

Takeaways

• 😀 Glaciers once covered the UK, shaping the landscape during the last Ice Age 18,000 years ago.
• 🌍 Glaciers were crucial in transforming mountains and valleys, leaving behind the landforms we see today.
• 🏔️ Glaciers are born in quarries or 'Combes,' which form when snow collects in hollows on mountainsides.
• ❄️ The ice in glaciers moves due to the pressure from the ice above, a process called rotational slip.
• 🪨 Freeze-thaw weathering occurs above the glacier as water freezes and thaws, gradually breaking apart rocks.
• 🪶 Stones and debris from the glacier's movement cause abrasion, deepening and smoothing the land.
• 🔨 Plucking is when the glacier lifts large rocks, creating steep back walls and armchair-shaped hollows.
• 🌄 Glaciers carve U-shaped valleys, turning V-shaped valleys into glacial troughs through abrasion and plucking.
• 🌧️ Smaller glaciers leave hanging valleys in the larger troughs due to their limited erosive power.
• 🌊 Meltwater from the glaciers created tons of sediment and erratic stones, which were carried down the mountains.
• 🧠 To understand the presence of glaciers in the UK, you need to look for clues in the landscape and use your imagination.

Q & A

What was the primary factor that shaped the landscape in the Lake District during the last ice age?

The primary factor that shaped the landscape was the glaciers that covered the region during the last ice age, around 18,000 years ago. These glaciers transformed the landscape through processes such as erosion and deposition.

What is a 'combe' and how did it form?

A 'combe' is a type of quarry or hollow formed in the mountainside. It was created when snow collected year after year in a depression, eventually turning into compact ice, which then began to move and erode the surrounding rock.

What is 'rotational slip' and how does it relate to glacier movement?

'Rotational slip' refers to the movement of ice within a glacier. As the ice at the bottom melts due to pressure, the glacier can slide over the rock beneath it, much like how a person might slide down a car seat. This movement is key to the glacier's erosion process.

How does freeze-thaw weathering contribute to the erosion process?

Freeze-thaw weathering occurs when water enters cracks in the rock, freezes, and expands. This expansion causes the rock to crack further. Over time, this process weakens the rock, and it eventually breaks apart, adding debris to the glacier.

What is the term for the stones that fall onto the glacier from the surrounding landscape?

The stones that fall onto the glacier are called 'scree.' These fragments of rock are picked up by the glacier as it moves and contribute to the glacier's erosion.

What is 'abrasion' and how does it affect the landscape?

Abrasion is the process by which rocks and debris embedded in the glacier scrape against the bedrock beneath it. This action erodes the landscape, smoothing and deepening the rock surface over time, similar to the effect of sandpaper on wood.

What is 'plucking' and how does it contribute to glacier erosion?

Plucking occurs when the glacier melts and refreezes around large rocks. This causes the rocks to be lifted from the bedrock and carried along by the glacier. Plucking contributes to the formation of steep back walls and armchair-shaped hollows in the landscape.

How did glaciers transform the v-shaped valleys in the Lake District?

Glaciers transformed v-shaped valleys into u-shaped valleys, also known as glacial troughs, through the processes of abrasion and plucking. The glacier's movement deepened and widened the valley, giving it a u-shape.

What are hanging valleys and how do they form?

Hanging valleys are smaller, higher valleys that are left behind when a larger glacier cuts through a region. These valleys are typically found in the walls of glacial troughs, formed by smaller glaciers that did not have enough erosive power to carve as deeply.

What are 'erratic stones' and how do they relate to glacial movement?

Erratic stones are large boulders that were carried by glaciers from their source region and deposited in areas where they do not naturally belong. These stones are evidence of the glaciers' immense power and their ability to transport rock over great distances.