Sentence:  The theory of a rise of a dome of strata from beneath the sea and the <WSD>offthrow</WSD> of the waters on all sides from that dome, their escape through lateral fractures in the upheaved chalk, together with a slow wearing back of the fractured and denuded edges of the chalk in the form of cliffs, ... 
Meaning of the word marked with <WSD> tags:  The act of throwing off;  liberation