- Estuary – a place where rivers meet the sea. In Long Island Sound, freshwater from rivers, runoff, and groundwater mix with saltwater from the Atlantic Ocean.
- Moraine – a mass of rocks and sediment carried down and deposited by a glacier, typically as ridges at its edges or extremity.
- Long Island Sound did not always exist. The area was once a broad plateau.
- The Hammonasset Moraine trail is a terminal moraine.