The correct option is 1 and 2 only.
Explanation
Parabolic dunes are U-shaped or scoop-shaped mounds of sand that form in areas where vegetation covers parts of the sand. They are classified as aeolian (wind-driven) depositional landforms.
Statement-wise Analysis:
- Statement 1 is Correct: Parabolic dunes typically develop when sandy surfaces are partially covered with vegetation. The vegetation anchors the sand at the sides (wings), while the central part of the dune remains loose and is pushed forward by the wind.
- Statement 2 is Correct: In terms of shape, parabolic dunes resemble barchans but are oriented in the opposite direction relative to the wind. Therefore, they are often described as "reversed barchans."
- Statement 3 is Incorrect: Unlike barchans, where the wings (horns) point away from the wind (downwind), the wings of a parabolic dune point towards the wind direction (upwind). This occurs because the vegetation holds back the arms while the central sand migrates leeward.
Key Takeaway:
The primary distinction between a Barchan and a Parabolic dune is the orientation of their wings: Barchan wings point downwind (away from wind), whereas Parabolic dune wings point upwind (towards wind) due to vegetation anchoring.