The writers found some block streams in the Kantô Mountains (these localities and details are as in table). The distribution of the trees on the block streams and lichen covering the blocks indicates that additions of new materials have virtually ceased. The lack of the matrix indicates that under periglacial condition, blocks were produced by mechanical weathering in full flourish resulting from frost action and moved downward on the slope by the mass wasting. Therefore, the writers consider that these block streams are of the fossil periglacial morphology.