The correct option is 1 only
Explanation
Eskers are significant depositional landforms produced by glacio-fluvial action. They represent the accumulation of debris transported by meltwater streams associated with stationary or retreating glaciers.
Statement-wise Analysis:
- Statement 1 is Correct: Eskers appear as long, sinuous ridges that resemble embankments. They are composed of very coarse materials, such as boulders and blocks, along with sand and gravel. These materials are deposited when the velocity of the meltwater stream decreases, preventing the transport of heavier sediments.
- Statement 2 is Incorrect: Eskers are primarily formed by streams flowing beneath the glacier (subglacial streams) or within the ice (englacial streams), rather than streams flowing over the surface. The water flows through tunnels at the base of the glacier, depositing sediment on the valley floor, which remains as a ridge once the ice melts.
- Statement 3 is Incorrect: Eskers are depositional features formed by glaciers (specifically meltwater). They are neither erosional features nor formed by wind. Common wind-formed erosional features include yardangs and mushroom rocks.
Key Takeaway:
Eskers are sinuous ridges of stratified sand, gravel, and boulders deposited by subglacial meltwater streams. They are distinct from moraines, which are deposits of unsorted till formed directly by the movement of glacial ice.