Glacial landforms: Statement I says that portions of glacial troughs may show remarkably flat valley floors, and Statement II says that this flat floor in a glacial trough is produced by uniform glacial erosion. What is the correct relationship between these statements?

Introduction / Context:
This question focuses on glacial geomorphology, particularly on glacial troughs, which are U shaped valleys carved by moving ice. Two statements are given about flat valley floors in these troughs and their origin. The learner must decide whether each statement is true and whether the second statement explains the first. Understanding how glaciers erode rock and shape valleys is key to solving this item.

Given Data / Assumptions:

• Statement I: Portions of glacial troughs may exhibit remarkably flat floors.
• Statement II: The flat floor in a glacial trough is produced by uniform glacial erosion.
• We assume standard descriptions of U shaped valleys and glacial erosion processes from physical geography.

Concept / Approach:
Glaciers are powerful agents of erosion. As they move, they abrade bedrock and pluck blocks from valley sides and floors. Over time, this action transforms a former V shaped river valley into a U shaped glacial trough with steep sides and a relatively flat or gently sloping floor. The concept of uniform glacial erosion along the valley floor explains the creation of that flatness. The approach is to assess whether each statement reflects this mainstream understanding.

Step-by-Step Solution:
Step 1: Evaluate Statement I. Glacial troughs, such as those in formerly glaciated mountain regions, commonly show flat or broad floors. This is a central characteristic used to distinguish them from V shaped river valleys, so Statement I is true. Step 2: Examine Statement II. Uniform glacial erosion along the valley floor, including abrasion and plucking, tends to remove irregularities and deepen and widen the valley, producing a smoother, flatter bottom over long periods. Step 3: Because the glacier occupies much of the valley cross section, erosion acts widely rather than being confined to a narrow channel, which contributes to the flatness of the trough floor described in Statement I. Step 4: Therefore, Statement II describes the process that leads to the landform property mentioned in Statement I. Step 5: Both statements are factually correct, and the second statement provides the correct geomorphic explanation for the first.

Verification / Alternative check:
To verify, one can recall classic field examples of glacial troughs such as those in alpine regions. Photographs and diagrams show broad, flat or gently graded floors that contrast clearly with the sharp V shaped profiles left by river erosion. Geomorphology texts emphasise that this form develops because of the extensive bedrock erosion by glaciers, which tends to act across the whole valley cross section, supporting the explanation in Statement II. This agreement with the standard model of glacial erosion confirms that the given combination is correct.

Why Other Options Are Wrong:

• Both true but Statement II not the explanation: This ignores the direct causal link between uniform glacial erosion and flat valley floors, which is central to understanding glacial trough formation.
• Statement I true, Statement II false: Uniform glacial erosion is not false; it is the accepted explanation for the valley floor shape.
• Statement I false, Statement II true: Statement I is not false, because flat floors in glacial troughs are well documented.

Common Pitfalls:
Some learners may confuse glacial troughs with river valleys and incorrectly expect a V shaped cross section, leading them to question Statement I. Others might think that glaciers erode only at certain points rather than relatively uniformly along the valley floor, causing doubt about Statement II. Remember that glaciers, unlike narrow rivers, can fill a valley and erode broadly, transforming the original shape into a typical U shaped trough with a comparatively flat floor.

Final Answer:
Both statements are individually true, and Statement II is the correct explanation of Statement I.