noboribetsu
. The Noboribetsu Primeval Forest In 1924, the forest around Noboribetsu-Onsen Hot Springs was nationally protected and designated as the "Noboribetsu Primeval Forest". In those days, the forest comprised mainly typical gigantic trees found in south Hokkaido, such as Mongolian oak and Caistor aralia. Later, however, the forest changed much as a result of logging activities in the last years of World War II and the destructive forces of Typhoon Toyamaru in 1954. You can still find towering querus crispula trees here and there. From these, you will be able to imagine the former glory of the primeval forest.
. History of Jigokudani Valley
Mt. Kuttara, the central crater of which is where Kuttarako Lake is located, began volcanic activities again in its western foot in the beginning of the Holocene epoch (10,000 years ago to the present). Thousands of years of repeated erratic explosions produced the geographical features around Jigokudani Valley. High volcanic energy in the form of magma is believed to be stored underground. Gas is emitted and hot water spouts out actively even now.
. Plants around Jigokudani Valley
Although the elevation of Jigokudani Valley is only 210 to 260 meters, such alpine plants as Marsh tea, and Crowberry, grow there. This is because the surrounding environment is very severe for plants due to such emitted gas as hydrogen sulfide or the presence of the highly acidic and moisture absorbing grass. Such severe conditions, like severe weather on high mountains, impede growth of plants other than Alpine plants.
This big rock was formed about 50000 years ago when Mt. Kuttara erupted. Heavy gravel spewed by the eruption fell around the mountaintop and ran down its slope. Pieces of the gravel piled up and melted together to form the rock.