Question

What does a valley glacier create at the point where it starts? A) esker C) till B) moraine D) cirque

Short answer

D) Cirque

Step-by-step solution

Understand the Geography Concepts

You need to understand each term associated with glaciers to figure out which one is relevant to where a valley glacier starts. A valley glacier is a type of glacier that forms in a mountain valley and moves down the valley, carving it as it progresses.

Define the Terms

- **Esker**: A long, winding ridge of post-glacial gravel and other sediment. It is formed by streams that flow under glaciers. - **Till**: Unsorted glacial debris that is directly deposited by a glacier. - **Moraine**: Accumulation of dirt and rocks that have fallen onto the glacier surface or have been pushed along by the glacier as it moves. - **Cirque**: A bowl-shaped depression on a mountainside that serves as the head of a glacier.

Identify Glacial Features at Start Points

A cirque is created at the start of a valley glacier because it forms the glacier's birthplace, where the snow accumulates and turns into ice. Moraine and till are associated with glacier movement and deposition, while eskers are not formed at the start of glaciers.

Select the Best Answer

Since a cirque is specifically a bowl-shaped depression formed where a glacier begins, the correct answer to the question of what a valley glacier creates at the point where it starts is D) Cirque.

Key concepts

Cirque Formation

Cirque formation is an essential process in glaciation, particularly in mountain regions. A cirque begins as a small hollow on a mountainside where snow accumulates over time. Gradually, the accumulated snow becomes compacted, turning into ice. This ice starts to melt slightly at the bottom, causing it to erode the rock beneath, forming a bowl-shaped depression.
Over the years, this erosion deepens and widens the cirque. The cirque becomes the starting point or the 'nest' of a valley glacier. This amphitheater-like hollow often contains a small lake, called a tarn, which remains after the glacier has melted away. Key processes involved in cirque formation include:

• Accumulation of snow
• Compaction into ice
• Melting and erosion
• Formation of a basin-shaped hollow

These processes contribute significantly to the dramatic landscapes seen in alpine environments.

Valley Glacier

Valley glaciers, which form primarily in mountainous regions, are responsible for carving out the valleys they inhabit. They are masses of ice that flow in between the walls of a valley much like a river. The movement of valley glaciers is primarily driven by gravity and the pressure of the accumulating ice.
Glaciers move at varying speeds, with their rate being influenced by factors such as the slope of the valley, the temperature, and the amount of meltwater lubricating its base. This gradual movement not only shapes the valley itself but smoothens its floor and sides. As a valley glacier advances, it transports rocks and soil, reshaping the landscape. Key features of a valley glacier include:

• Massive ice flow in a mountainside valley
• Sculpting of sharp ridges and U-shaped valleys
• Transportation and deposition of rock debris

Understanding valley glaciers is crucial for comprehending how past glacial activity has shaped current geographical features.

Glacial Landforms

Glacial landforms are the distinct features created by the movement and melting of glaciers. These landforms are important indicators of past glacial activity and help scientists understand the dynamics of Earth's climate over geological timescales.
Glacial landforms include a wide range of structures, from the imposing tales of Eskers and Moraines to the subtle beauty of Cirques and Tarns. Some notable glacial landforms are:

• Cirques: Bowl-shaped depressions at the heads of glaciers.
• Eskers: Long, winding ridges formed by meltwater streams under glaciers.
• Moraines: Accumulations of dirt and rocks, formed at the sides or terminal end of a glacier.
• Drumlins: Smooth, elongated hills formed by glacials moving across debris.

Each of these landforms provides insight into the processes occurring during a glacier's lifecycle, from formation high in the mountains to where it flows and eventually melts.