Before revision: Irregularities in the underlying terrain halt the slide of the peat, causing flarks to form downslope from the obstruction as the downslpe peat tears away from the portion of the peat mass held back by the underlying obstruction.
After revision: Irregularities in the underlying terrain halt the slide of the peat, causing flarks to form downslope from the obstruction as the downslope peat tears away from the portion of the peat mass held back by the underlying obstruction.