The chalk itself's composed by plankton which has fallen down from the sea surface onto the sea floor, so that 90 percent of the sediment here is skeleton of living stuff, and then you have that millimeter-thick red layer, and then you have black rock.
白亜自体はプランクトンが 海面から海底に沈んで堆積して できたので ここに見える 沈殿物の90%は生命体の残骸です そしてミリ単位幅の赤い層と それに黒い岩石があります