Upheaved plug domes are masses of rock that are pushed bodily upwards like pistons. "Showa Sin-Zan " or "New Roof Mountain" grew during the height of the Second World War, so there were no official records of its growth, but the astute village postmaster, Masao Mimatsu, kept a unique pictorial record of its progress by drawing a series of profiles on the paper covering of his window. From January 1944 until November 1944 the uplifted area rose steadily, but no new rock was visible -- the uplifted material was all crater lake sediments, baked hard by the heat of the lava beneath, carried upwards as smoothly as if on an elevator. In November of 1944, a plug of lava eventually punched its way through the elevated dome, rising until it was about 100 m above the top of the dome, and nearly 300 m above ground level. It is this extrusive crown which dominates the photo. (Fig. 7.28).

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