A long, narrow, sinuous ridge of stratified sand and gravel of glacial origin is known as

• A. Esker
• B. Moraine
• C. Drumlin
• D. Outwash plain

Answer: (A)

This describes an esker. Eskers are long, narrow, sinuous ridges of stratified sand and gravel that form from meltwater streams flowing within or beneath a glacier. As water drains through subglacial channels, it deposits sorted sediments in the channel floor, creating a continuous, often winding ridge. When the ice retreats, these sediment-filled channels remain as recognizable sinuous ridges.

This fits better than moraines, which are unsorted piles of till laid down at the glacier’s edge; drumlins, which are elongated hills formed from till and reshaped by ice flow; or outwash plains, which are broad, flat expanses of stratified sands and gravels deposited beyond the glacier, not a narrow ridge.