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Eskers: winding ridges left by glacial meltwater rivers

All year

An esker is a long, winding ridge of sand and gravel left by a meltwater river that flowed in a channel within or beneath the last ice sheet. Eastern Massachusetts has several on conservation land and town land, and you can walk along the top of one.

Why this time of year

Eskers do not change with the seasons, so any month works. In winter and early spring, look for the ridge's outline through the bare trees.

How to notice it

  1. On a trail marked as an esker or ridge, notice that the path runs along a narrow, raised, winding line, often with the ground dropping away on both sides.
  2. Look at the ground where the soil is exposed, such as a trail edge or a tree-root hollow. Esker material is mostly sand and gravel, sometimes with bigger stones mixed in.
  3. Look down both sides of the ridge and notice what lies at its foot.
  4. Stay on the marked trail and keep off the steep sides.

Try this with kids: Walk along the top of the ridge and count how many times it bends. Then picture a river running through a channel in the ice right where your feet are.

Word to know: “Esker”: a long, narrow, winding ridge of sand and gravel made by a meltwater stream that ran inside or beneath a glacier.

Safety

  • Stay on marked trails; ridge sides can be steep and sandy.
  • Ridge trails can be steep or hilly; check the property's own trail notes before bringing strollers or small children.

Sources

  • home.nps.govNPS: eskers are meandering ridges of sediment formed in water channels beneath or within glacier ice.
  • dmr.nd.govNorth Dakota Geological Survey: eskers are winding ridges of gravel and sand from streams in ice-walled channels, most likely tunnels; sand and gravel deposited as meltwater slows.
  • massaudubon.orgMass Audubon trails page: its trails include drumlins and eskers.
  • nsrwa.orgNSRWA listing for Great Esker Park, Weymouth: esker is a long ridge of sediment and gravel left after glacial retreat; trail along the ridge top.
  • avisandover.orgAVIS, Indian Ridge Reservation, Andover: the Indian Ridge esker reaches up to 50 feet.

Checked against these sources on October 20, 2026.

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