Smooth oval hills composed mainly of boulders or glacial sands and gravels are known as

Answer Details

Drumlins are smooth, oval-shaped (egg-shaped) hills composed of glacial till - a mixture of boulders, sand, gravel, and clay deposited by a glacier. They are typically 1-2 km long and 300-600 m wide, with a steeper end (stoss) facing the direction from which the glacier advanced and a gentler, tapering end (lee) pointing in the direction of ice flow.

Drumlins often occur in groups called drumlin swarms or a "basket of eggs" landscape. Their exact formation is debated, but they are shaped by the pressure and movement of the overlying ice sheet moulding previously deposited glacial material.

The other options are different glacial landforms:

• An arete is a sharp, knife-edged ridge formed by erosion between two adjacent cirques (corries). It is an erosional feature, not a depositional one.
• A moraine is a ridge or mound of unsorted glacial debris (till), but moraines are typically irregular ridges rather than smooth oval hills.
• An esker is a long, sinuous (winding) ridge of sand and gravel deposited by meltwater streams flowing beneath or within a glacier.