Question

Which forms when a rock in glacier ice slides over Earth's surface? A. moraine C. horn B. esker D. groove

Short answer

D. Grooves form when a rock in glacier ice slides over Earth's surface.

Step-by-step solution

Identify the Process

First, let's identify that we are dealing with a process involving glaciers moving over Earth's surface. Glaciers are massive bodies of ice that flow very slowly over land.

Understand the Definitions

Understand what each option represents: A moraine is an accumulation of rock debris deposited by a glacier. An esker is a long, winding ridge of sand and gravel. A horn is a sharp mountain peak sculpted by glaciers. A groove, in the context of glaciers, refers to the marks or cuts left on a surface by glacial movement.

Match the Process and Effect

Match the process (a glacier sliding over Earth's surface) to one of the given options. The sliding movement of glaciers typically erodes the surface below, creating grooves or striations as the rock embedded in the ice is dragged across the surface.

Select the Correct Option

Based on the process of a glacier's sliding movement over the Earth's surface, 'D. groove' best describes the result, as it refers to the marks created by this process.

Key concepts

Glacial Landforms

Glacial landforms are fascinating geological features created by the action of glaciers. These massive, slow-moving rivers of ice shape the landscape in various ways. Glaciers carry with them large amounts of rock debris, and their movement can carve out unique formations on the Earth's surface. Some key landforms created by glacial action include:

• U-shaped valleys: These valleys form as glaciers carve out the land beneath them, making the valley much deeper and wider than a typical river valley.
• Cirques: Bowl-shaped hollows found in mountains where a glacier starts its journey.
• Arêtes: Narrow ridges that form between two glacial valleys.

Each of these features provides a clue to the glacier's past movement and the power it had to reshape the land. Understanding these landforms helps geologists study the ancient landscapes and how they have changed over time.

Moraine

A moraine is a type of glacial landform that serves as an indicator of past glacial activity. It consists of accumulations of dirt, rocks, and other debris that have been transported and deposited by a glacier. The positioning and composition of moraines can tell us a lot about a glacier's path and size. There are several types of moraines:

• Lateral moraine: Found along the sides of a glacier. It accumulates when rocks and debris fall from the valley walls.
• Medial moraine: Forms when two glaciers meet and the debris from the inside edges of the glaciers converge.
• Terminal moraine: Marks the furthest advance of a glacier, often forming a ridge at the glacier's endpoint.

Moraines can vary in size and shape, but they play a crucial role in understanding glacial dynamics and past climates.

Glacial Movement

Glacial movement is a slow but powerful process that significantly impacts the Earth's landscape. Glaciers move under their own weight due to gravity, causing the ice to flow like a very slow river. There are two primary ways glaciers move:

• Plastic flow: The ice deforms internally without breaking; this occurs within the glacier, typically where the ice is thickest.
• Basal slip: The entire glacier slides over the bedrock, lubricated by a thin layer of meltwater at its base, which reduces friction.

This movement allows glaciers to erode the landscapes they pass over by picking up rocks and soil, which are then deposited in new locations as the ice melts. The process also creates glacial striations or grooves, as described in the exercise, which are essential for understanding past glacial paths and behaviors.

Geological Processes

Geological processes are natural mechanisms by which the Earth’s surface and structure are shaped and changed over time. Glaciers are significant agents in these processes. Here are some ways glaciers influence geology:

• Erosion: As glaciers move, they abrade and pluck material from the bedrock. This can carve out valleys and shape mountains, leading to features like fjords and arêtes.
• Deposition: Glaciers deposit the materials they have transported, forming distinctive landforms such as moraines and outwash plains.
• Landform Creation: The interaction between glaciers and the underlying land leaves behind various unique features once the ice retreats.

These processes are critical for scientists who study Earth's history. They provide vital clues to past climates and help predict future changes to our environment.