The phrase "ancient shorelines" refers to the old levels of land where the ocean or a large body of water used to meet the land long ago. Full definition
Pockets of gas trapped along ancient shorelines would have given them a cozy place to call home about 3.2 billion years ago. (sciencenewsforstudents.org)
Figuring out how far sea level rose during past warm periods in Earth's history starts with a walk on the beach, a keen eye for evidence of ancient shorelines, and a highly accurate GPS system. (ldeo.columbia.edu)
These may be submerged ancient shorelines cut during times of lower sea level, «the most recent of which occurred during the last glacial period, which ended about 19,000 years ago,» Chaytor said. (scientificamerican.com)