An esker is defined as which of the following?

• A. A circular mound formed by meteor impact
• B. A long narrow hill of sand and gravel in an area once covered by ice
• C. A shelf-like rock formation
• D. A tidal pool

Answer: (B)

Eskers are formed when meltwater streams flow through tunnels within or under a glacier, depositing sorted sand and gravel as they move. When the glacier retreats, these deposits remain as a long, winding ridge. That makes a long narrow hill of sand and gravel in an area once covered by ice the best description. The other features describe different landforms: a circular mound from meteor impact would be an impact crater; a shelf-like rock formation is a ledge or escarpment; a tidal pool is a coastal feature formed by tides. Eskers specifically reflect past glacial meltwater pathways and produce elongated, gravel-rich ridges.