This paper considers large-scale erosion of late medieval peatland landscapes along the inland lagoon rims of the north-eastern Zuyder Zee area (today: Noordoostpolder, the Netherlands) and integrates palaeogeographical reconstruction, material archeological and spatial archaeohistorical research. The dynamic regional history of coeval loss of peaty coastal plains and boom of maritime activities is studied from archaeological, geological and historical data perspectives. In the first half of the Middle Ages (a.d. 500-1000), vast peatlands and interconnected lakes characterised the study area. During the late Middle Ages (a.d. 1000-1500), increased storm surges and tidal incursions allowed for extensive progressive erosion of inhabited peatlands, transforming the central Netherlands into the Zuyder Zee tidal lagoon. In the north-eastern quadrant of the expanding water body, medieval terrestrial geological and archaeological records fell prey to erosion, re-working and uptake into lagoon-floor deposits. These deposits have been intensively surveyed since the 1940s when the quadrant was reclaimed and made into arable land, and are revealed to contain spatially clustered late medieval archaeological objects.