Eskers and marine deltas are among the most spectacular glacial landforms along the Ice Age Trail. Eskers are ridges of sand and gravel deposited in tunnels that formed at the bottom of the ice sheet. It is believed that meltwater and sediment first traveled freely along the tunnels, perhaps for tens of miles. During the late stages of ice retreat, the tunnels were clogged with sediments. When the ice had finally melted away, these tunnel fillings were left behind as esker ridges. They trend generally southward, parallel to the flow of the glacier, in contrast to moraines that trend east-west along the former ice margin.

Deltas are large, flat-topped bodies of sand and gravel that washed into the sea at the edge of the glacier. The sediments that built the deltas were transported through the same ice tunnels that eventually became the sites of esker formation. These sediments piled up on the sea floor when they reached the ends of the tunnels. At first, they accumulated as fan-shaped mounds on the ocean floor. In places, the sand and gravel were deposited in such large quantities that they eventually built up to the ocean surface and became full-fledged deltas. Each delta expanded seaward as sediments washed across the top and cascaded down the front. The elevation of the south rim of the delta top approximates the position of sea level when the delta formed.

Both eskers and deltas contribute in several ways to the Maine economy. The porous sand and gravel deposits store great quantities of water and thus are important aquifers. These glacial deposits also provide aggregate for construction, resulting in the gravel pits seen in many places along the Ice Age Trail. The sandy soils on eskers and deltas, as well as moraines, are favorable for growing blueberries. Commercial blueberry fields are especially important to the economy in eastern coastal Maine. You will see these large fields all across the area.

To read more about Maine in the Ice Age, check out these more indepth explanations: Marine Clay, Salt Marshes and Recent Sea Level Rise, Glacial Retreat, Moraines, Chronology, Abrupt Climate Change