Many bogs distributed in the mountains of Japan are characterized by their own vegetation. They are usually high-moors built up only by rain fall, and were formed by climatic changes during the Last Glacial Age. In this paper, climatic change was considered the key to the manner of the formation of montane bog, it was studied using borings and pollen analysis. Study areas were from the northern part of the Kanto district to the southern part of the Tohoku district, where many montane bogs are distributed. These bogs were formed in two short periods. One was after the Holocene warm period, namely hypsithermal, and the other was from the Last Glacial Age to the Holocene. The origin of some bogs was not lakes or ponds but the over-humidization of the ground. These bogs were formed when the climate became relatively more humid. The humidization at that time was caused by an increase in snowfall and also by changes in seasonal rainfall patterns.
