Question

What is a ridge formed by deposition of till called? A) striation C) cirque B) esker D) moraine

Short answer

Option D: moraine

Step-by-step solution

Understanding the Question

First, let's clarify what the question is asking. We're asked to identify which term describes a ridge formed by the deposition of till. Till refers to the unsorted material deposited directly by glacial ice.

Reviewing the Options

Next, let's examine the options provided: - Striation: These are scratches or gouges cut into bedrock by glacial abrasion. - Cirque: This is a bowl-shaped, steep-walled mountain basin, carved by glacial erosion. - Esker: A long, winding ridge of stratified sand and gravel, formed by glacial meltwater. - Moraine: An accumulation of glacial debris (till) formed at the edge or terminal snout of a glacier.

Identifying the Correct Option

Analyze the definitions to find which term correctly matches a ridge formed by deposition of till. A moraine specifically refers to an accumulation of glacial debris or till, often forming ridges at the edge of a glacier.

Conclusion and Answer

Based on the definitions, the term for a ridge formed from till is 'moraine' as it describes a deposit of unsorted glacial debris. This matches the features described as formed by till.

Key concepts

Till Deposition

Till is a type of geological material directly deposited by a glacier. It is characterized by its unsorted nature, as glaciers transport a wide array of particle sizes, ranging from fine grains to large boulders.
This makes till distinctive from materials sorted by water or wind.
When the glacier moves, it picks up this debris, carrying it along its path and ultimately depositing it, creating various glacial landforms. Till deposition occurs primarily during the glacier's melting phase when the ice releases its load of rocks and sediment.
This can happen

• underneath the melting glacier
• at the glacier's front (also known as the terminus)
• or along the glacier's sides

The unsorted mixture of till is plastered onto the landscape, creating a range of topographical features.

Moraine

Moraines are the direct result of till deposition by glaciers, forming as ridges or accumulations of debris left behind.
There are several types of moraines, each dependent on their location relative to the glacier:

• **Lateral Moraines**: Formed along the sides of a glacier, where the glacier erodes the valley walls and carries debris downhill, piling it along the edges.
• **Medial Moraines**: Occur when two glaciers merge, and their lateral moraines combine to form a single ridge of debris down the center of the combined glacier.
• **Terminal Moraines**: These mark the furthest advance of a glacier, forming large mounds of till at the glacier's terminus.
• **Ground Moraines**: Blanketlike layers formed by the direct deposition of till beneath the glacier, leading to a more subtle and uneven landscape.

Understanding moraines is vital in studying past glacial activity, as their composition and location offer clues about the glacier's size, movement, and melting patterns.

Glaciation Processes

Glaciation processes encompass the complex series of events that lead to glacier formation, movement, and subsequent melting. This process involves a dynamic interplay of geological and climatic factors: **1. Accumulation** This is the initial stage, where snowfall compacts into ice over time, thickening as it builds up layers. This is primarily influenced by:

• **Temperature**: Cold conditions transform snow into dense glacial ice.
• **Precipitation**: Frequent snowfall enhances accumulation and ice formation.

**2. Movement** Once enough ice mass is accumulated, gravity propels the glacier to move. This movement is crucial for eroding and transporting till. Crucial factors include:

• **Slope**: Glaciers generally move downhill, following the steepest descent.
• **Basal Sliding**: The glacier slides over its bedrock due to melting ice acting as a lubricant.

**3. Ablation** This process involves the loss of glacier mass, mainly through melting, sublimation, or calving. As glaciers lose ice:

• **Melting**: Most pronounced at lower altitudes, contributing to till deposition.
• **Calving**: Direct ice loss into water bodies, forming icebergs.

Each stage of glaciation has a significant impact on the landscape, shaping the terrain and creating distinctive landforms, including moraines, as mentioned earlier. By studying these processes, scientists can better understand climate change and its impact on glacial regions.