Glacial Processes and Landforms

Summary

This video explores the fascinating dynamics of glaciers, from their formation to their erosive and depositional processes. It covers the two main types of glaciers—continental and alpine—and describes how they shape landscapes through mechanisms like plucking, abrasion, and freeze-thaw. The script also delves into features such as moraines, erratics, and u-shaped valleys. Special emphasis is placed on New Zealand's glaciers, highlighting the Franz Josef and Tasman glaciers, as well as the impact of climate change on glacier retreat. The video also explains how glaciers form distinctive landforms like fjords, hanging valleys, and tarns, showcasing their immense power and beauty.

Takeaways

• ❄️ Glaciers are massive, moving rivers of ice found on land, formed from compacted snow over long periods of time.
• 🌍 There are two main types of glaciers: continental glaciers, which cover large land areas like Antarctica and Greenland, and alpine glaciers, found in mountainous regions such as New Zealand’s Southern Alps.
• 💧 Glaciers have distinct zones — the zone of accumulation where snow builds up, and the zone of ablation where melting and evaporation occur.
• 📉 The balance between accumulation and ablation determines whether a glacier advances or retreats; this is known as the glacial budget.
• 🌡️ During cooler global climates, glaciers expand (glaciations), while warmer periods cause them to retreat (interglacials).
• 🪨 Glacial erosion occurs mainly through plucking and abrasion, shaping the landscape by removing and grinding rock surfaces.
• 💥 Glaciers transport large quantities of rock and debris, which can be deposited as moraines, drumlins, till, and erratics when the ice melts.
• 🏔️ Glacial erosion creates distinct landforms such as U-shaped valleys, cirques (corries), arêtes, pyramidal peaks, fjords, and hanging valleys.
• 🌊 When glaciers retreat, meltwater often forms lakes like kettle lakes, tarns, ribbon lakes, and glacial lakes behind terminal moraines.
• 🧊 Calving occurs when chunks of ice break off the end of a glacier, forming icebergs in lakes or the sea.
• 💎 Rock flour — fine sediment produced by glacial grinding — gives many glacial lakes their distinctive turquoise color.
• 🚶‍♂️ The South Island of New Zealand provides vivid examples of glacial features, including fjords, moraines, and valleys, illustrating the ongoing and past effects of glaciation.

Q & A

What are the two main types of glaciers?

The two main types of glaciers are continental glaciers and alpine glaciers. Continental glaciers are massive and cover large areas, such as Antarctica and Greenland. Alpine glaciers form in mountainous regions.

What is the process through which snow becomes ice in a glacier?

Snow becomes ice in a glacier through compaction. Over time, new layers of snow compress the older layers, squeezing out the air and causing the snow to compact and transform into ice. The ice turns bluish as the air is squeezed out.

What is the 'zone of accumulation' in a glacier?

The zone of accumulation is the area where snow falls and accumulates, typically at the highest elevation on the glacier. It is the region where new ice forms, contributing to the growth of the glacier.

What happens in the 'zone of ablation' of a glacier?

In the zone of ablation, most of the glacier's ice melts or evaporates. This zone is located further down the glacier and experiences the loss of ice due to melting, sublimation, and calving.

What is meant by a glacier being in 'retreat'?

A glacier is said to be in retreat when the rate of melting and ablation exceeds the rate of ice accumulation in the zone of accumulation. This results in the glacier shrinking, and its terminus (end) moving backward.

What is a kettle pool and how is it formed?

A kettle pool is formed when a glacier retreats and leaves behind a block of ice. The ice eventually melts, creating a depression in the landscape that fills with water, forming a pool.

What are crevasses, and why are they dangerous?

Crevasses are deep cracks that form in glaciers due to the movement of the ice. They can be very dangerous to climbers because they are often hidden by snow and are difficult to detect.

What is the main erosive process of a glacier?

The main erosive process of a glacier is called plucking. As the glacier moves, the ice melts slightly around rocks and boulders, which are then frozen into the glacier. These rocks are eventually plucked from the ground as the glacier moves.

What is a terminal moraine?

A terminal moraine is a type of glacial deposit formed at the furthest point a glacier reaches during its advance. It is made up of debris like rocks, sand, and clay, and can act as a dam, forming lakes.

How do glaciers contribute to the formation of fjords?

Glaciers carve out deep U-shaped valleys, and when these glaciers retreat, rising sea levels can flood the valleys, creating fjords—coastal landscapes with steep cliffs and irregular coastlines.