Matching Dune Types with Their Forms and Positions

This question requires matching different types of sand dunes, listed in List I, with their specific characteristics regarding form and position, as described in List II. Let's analyze each dune type and find the correct match based on geomorphological definitions.

List I: Dune Types

List II: Form and Position Descriptions

Dune Type Analysis and Matching

Let's break down each dune type from List I and match it with the most appropriate description from List II:

A. Lee Dune Matching

A Lee dune forms on the leeward (downwind) side of a barrier or obstruction, such as a hill, cliff, or even a large vegetation patch. It is essentially an area where wind velocity decreases, causing sand deposition. These dunes are often elongated parallel to the dominant wind direction or the obstruction itself.

Description 3, "Elongated down-wind from topographic obstruction", accurately describes a lee dune.

Therefore, A matches with 3.

B. Fore Dune Matching

Fore dunes are the first line of dunes built on a beach or coastal plain, usually parallel to the shoreline. They are actively growing dunes, often stabilized by pioneer vegetation. While typically linear, they can sometimes take on a sinuous or arcuate shape depending on coastal irregularities or the presence of minor obstacles.

Description 4, "Roughly arcuate with arms extending down-wind either side of obstruction", best fits the morphology described, potentially interpreting the shoreline or coastal features as the 'obstruction'. While not perfectly fitting the typical linear description, it's the most plausible option among the choices for a fore dune in this context.

Therefore, B matches with 4.

C. Lunette Matching

A Lunette is a crescent-shaped dune found typically on the leeward side of playa lake beds (dry lake beds) or salt pans in arid and semi-arid regions. They are often composed of fine material derived from the lake bed, sometimes including gypsum or lime. The characteristic crescent shape often has its concave side facing the prevailing wind (windward).

Description 2, "Crescent-shaped opening upwind", accurately describes the shape and orientation of a lunette, where the 'opening' refers to the concave windward face.

Therefore, C matches with 2.

D. Climbing Dune Matching

A Climbing dune forms when sand accumulates on the windward slope of a steep topographic barrier, such as a mountain slope or cliff face. The wind carries sand up the slope, leading to dune formation that appears to 'climb' the obstruction.

Description 1, "Irregular accumulation rising up windward side of large topographic obstruction", precisely defines a climbing dune.

Therefore, D matches with 1.

Final Code Selection

Based on the matching:

• A → 3
• B → 4
• C → 2
• D → 1

The correct code representing this sequence is 3 4 2 1.