The Sanbe Azukihara Buried Forest is an exceptionally rare natural heritage site in Sanbe Town, Oda City, Shimane Prefecture, where an ancient forest from the Jomon period has remained remarkably well preserved underground. Today, the site is protected and presented at the Sanbe Jomon Forest Museum, also known as the Sanbe Azukihara Buried Forest Park, where visitors can see the ancient trees in a specially designed underground exhibition facility.
The buried forest is designated as a Natural Monument of Japan and is also an important component of the Japan Heritage story “The Eternal History Told by the Volcanoes of Iwami.” It offers a fascinating glimpse into the natural environment of Japan thousands of years ago.
The most remarkable feature of the Sanbe Azukihara Buried Forest is that many of its enormous trees remain standing upright with their roots still in the ground. In many buried forests, only the bases of trees survive. Here, however, giant cedars more than 10 meters tall and up to approximately 2.5 meters in diameter remain standing, creating an extraordinary scene that looks as though time itself has stopped.
Approximately 30 standing trees have been confirmed, along with more than 100 fallen trees. About 80 percent of the preserved trees are cedars, while other species include horse chestnuts, zelkova, and various oak trees. Together, these remains provide valuable evidence of the rich forest environment that existed during the Jomon period.
The preservation of this ancient forest is closely connected to the volcanic activity of Mount Sanbe. Approximately 4,000 years ago, an eruption of the Sanbe volcano caused debris flows and pyroclastic flows to fill the surrounding valleys, rapidly covering the forest.
Normally, such powerful natural events would flatten trees. In this area, however, the force of the debris flow weakened and a natural sediment dam formed. These unusual conditions allowed many of the trees to remain standing as they were buried.
Volcanic ash and sediment then accumulated above the forest. Groundwater covered the buried trees and prevented prolonged contact with air, slowing the decomposition of the wood. This combination of geological and environmental conditions made it possible for the forest to survive for thousands of years.
The geological layers surrounding the buried forest can be broadly divided into three sections. The lowest layer consists of deposits from the debris flow, followed by a layer formed by pyroclastic flows. Above these is a layer of volcanic ash transported and deposited by water.
These layers preserve detailed information about the natural environment and volcanic disasters of the period, making the site something of a “history book of the Earth.” Ancient soil also contains traces of fallen leaves and insects, providing important clues about the ecosystem that existed during the Jomon period.
A buried forest is a forest from the distant past that has been preserved underground in approximately the same location where the trees originally grew. Such sites are sometimes described as “fossil forests.”
More than 30 buried forests have been reported in Japan, but examples in which long tree trunks remain standing upright and are preserved on such a remarkable scale are extremely rare. The Sanbe Azukihara Buried Forest is therefore highly significant for both its size and exceptional state of preservation.
The buried forest is displayed in an underground exhibition facility built around the original excavation site. The enormous excavation pit is approximately 30 meters in diameter and 13.5 meters deep, allowing visitors to descend into the exhibition space and experience something like stepping directly into a prehistoric forest.
Standing beside the enormous trees gives visitors a powerful sense of their true scale—something that photographs cannot fully convey. Traces of fallen leaves and insects can also be seen around the tree roots, creating a remarkable impression of traveling thousands of years back in time.
The existence of the buried forest first became known in 1983, when standing trees were uncovered during agricultural land improvement work. The discovery initially attracted little attention, but subsequent investigations by volcanic researchers revealed its exceptional scientific value.
Full-scale excavation research began in 1998, leading to the discovery of numerous buried trees. Radiocarbon dating showed that the trees dated from the late Jomon period, approximately 3,500 to 3,700 years ago, attracting significant academic and public interest.
The Sanbe Azukihara Buried Forest is far more than an exhibition of ancient trees. It is a place where visitors can experience the immense power of nature and gain a deeper understanding of the history of the Earth and human life.
Guided tours and explanatory programs are also available, helping visitors learn more about how the forest was buried and the geological processes involved. The museum shop offers souvenirs made using buried wood, providing a unique way to remember the experience.
The buried forest is located at the foot of Mount Sanbe, an area rich in natural scenery. Visitors can combine their visit with other attractions around the mountain, making it an excellent destination for travelers interested in geology, archaeology, Japanese history, and nature.
The museum is approximately 20 minutes by car from JR Oda-shi Station. Driving is a convenient option, especially for travelers planning to explore the wider Mount Sanbe area.
If traveling by bus, get off at the nearest Chigo-bashi bus stop and walk for approximately 20 minutes. Because public transportation services in the mountainous area may be limited, checking the timetable in advance is recommended.
The Sanbe Azukihara Buried Forest is a remarkable heritage site created through an extraordinary combination of volcanic activity, geological conditions, and the forces of nature. The sight of a forest from thousands of years ago preserved almost as it stood offers a rare opportunity to contemplate the long history of the Earth and the lives of people who once lived in the Jomon period.
For travelers exploring Shimane and the Mount Sanbe area, a visit here offers an unforgettable encounter with a world that has remained hidden underground for thousands of years.