In the context of wind action, rocks with a narrower base and wider top are called:

The correct option is

Mushroom rocks

Explanation

In arid and semi-arid regions, wind acts as a prominent exogenic agent. Through the mechanical process of abrasion, wind-transported particles erode rock surfaces, creating specific erosional landforms.

Detailed Analysis:

• Mushroom Rocks: The rock formation described, characterized by a narrower base and a wider top, is known as a Mushroom Rock or Pedestal Rock.
• Mechanism of Formation: The abrasive power of wind is not uniform vertically. The wind carries a higher concentration of sand grains and coarser particles close to the ground surface.
• As a result, the erosion (undercutting) is more intense at the base of the rock compared to the top. Over time, this differential erosion creates a structure resembling a mushroom.
• Other Options:
  • Table rocks generally refer to flat-topped elevations like mesas.
  • Pillar rocks typically refer to vertical columns often formed by water action or differential weathering, not specifically the undercut shape of wind erosion.
  • Dune rocks would imply lithified sand dunes (depositional features), whereas the feature in question is erosional.

Key Takeaway: Mushroom rocks are classic erosional landforms in deserts caused by the differential abrasion of wind, which is most effective near the ground level.