Blankenham, Blokzijlerdijk, cropmarks. The drought clearly show the difference in soil type, between the peat soil of the Weerribben and the sea clay soils in the Noordoostpolder lies a strip of Loss tertiary and terrace slope soils, recognisable by the red colour..© 24 juli 2018 Marco van Middelkoop/Aerophoto-Schiphol