Chichibu Geopark

The strip-like white patterns running in succession inside the metamorphic rock (en echelon vein) is called a Gankomyaku (literally means "the vein of the flight formation of geese" in Japanese) as it evokes an imagery of wild geese flying in succession.

An en echelon vein is a crack that occurs in the process of rock rising from deep underground, and the gap of the crack is filled with white quartz and calcite.

Horaijima is a sandbank island made through erosion caused by the water of Arakawa River. It also has a promenade as a park.

Inside the park, you can see an S-shaped crustal fold that was formed due to the twisting of rocks deep underground.

The entire Nagatoro region is made of crystalline schist, which was formed as a result of volcanic products, mud, and sand deposited on the sea bed that was blended with the oceanic plate 20–30km or deeper underground in the Cretaceous period (approx. 80 million years ago) and exposed to enormous pressure. Crystalline schist is a thin layer of rock like a pie sheet that can be easily peeled off.

Iwadatami (a horizontal sheet of rock) is a river terrace that came into existence as a result of erosion of crystalline schist caused by water flowing from Arakawa River. Movements of faults have crushed the rock, and thus the area does not have the gravel that is supposed to cover the riverbed, resulting in an exposed bedrock. The rock cliff on the opposite shore that remained without being eroded is called Chichibu Red Cliff.

The brown part of Toraiwa is a mineral called stilpnomelane, and the white part that fills the cracks is a mineral called calcite. The rock took on this shape after being exposed to high pressure deep underground, and folding and piling on top of each other many times. The rock is said to have been named Toraiwa (literally means “tiger rock” in Japanese) because the pattern resembles the fur of a tiger.

There is also a monument engraved with a waka (poetry) that is said to have been made by Kenji Miyazawa, a famous Japanese poet and writer of children’s literature when he was out on a geological excursion in this area.

This is a magnificent outcrop of piemontite schist, which is rarely produced. Piedmontite is a beautiful mineral of dark violet and scarlet colors made from chert containing manganese. The downstream area from this rock is Nagatoro, which is a government-designated scenic beauty and natural monument.

There is also a large pothole on top of the rock. When this area was still part of the riverbed of Arakawa River in the past, rapid torrents had entered a depression of the rock and rotated swiftly, grinding the rock until creating a pothole.

Serpentine is a glossy rock with a dark green color, and it is called jamongan (literally means “snake mosaic rock” in Japanese) because the rock surface looks like snake skin. The rock becomes a beautiful stone material when polished and it is also referred to as “green marble.” Serpentine sourced from Chichibu is used in Japan’s Parliament Building.

Serpentine is prone to be worn down over time and also causes landslides. Even today, people avoid building highways and railways on top of areas containing serpentine.

This is a stratum back from the time when Paleo Chichibu Bay, which existed in the current location of Chichibu Basin from approximately 17 million to 15 million years ago, came into existence. Here, you can observe up close a discordance created as a result of a time difference between strata of close to 200 million years. It is designated as a national natural monument.

A fossil of an oyster can be observed at the protruding portion of the outcrop, serving as proof that shallow waters of Paleo Chichibu Bay had covered this area in the past.

Suisen-ji Temple is famous for being the last temple of worship on the Chichibu 34 Kannon Pilgrimage, and it is known as the “temple of expiration of term of a vow” of the Japan 100 Kannon Pilgrimage. It is told that people in the past who had completed their pilgrimage went into the grotto where spring water gushes forth to cleanse their bodies before returning to secular life.

In this area, you can also observe a Mélange, which was formed when masses of rock such as limestone and chert—that crumbled apart when the oceanic plate slid underneath the ocean trench—were mixed with mudstone.

This is a beautiful waterfall with a fall of approximately 12m that flows on top of the hard red rock of Chichibu belt called chert.

Chert in this region broke apart into pieces when the oceanic plate slid underneath the ocean trench and then mixed with mudstone, resulting in something called a Mélange, which comprises part of a mixture of large blocks of rock.

This is Japan’s largest sekitoba (stone stupa) made from a large crystalline schist from Samba River. The stone stupa is said to have been erected as an offering to the lord of the castle located in this place during the Namboku-cho period (in the 14th century). (Nationally designated historic site)

At a nearby mountain there are ruins of a mining site where this stone had been mined. The local stones, which are chlorite-schist, were referred to long ago as Chichibu ao-ishi (blue-green stone) and they were used as stone material in the entire Kanto region since the Jomon period.

During the Edo period, a torrential rain that lasted for four days caused the Arakawa River to flood, and the water level rose up to 18m, leaving even some parts of this area submerged in water. There is a rock with the Japanese character for water carved into it to indicate the water level at that time.

This area is the only place in the Chichibu Basin where water flows out, and as a result the river in this area is far more narrow than the rest of the river spread across the basin.

This had been a dangerous place of passage since the Edo period, where many people and horses slid down the cliff, and as a result the old road was widened through excavation during the Meiji period. The road runs through the top of Chichibu Sekiheki, which is a cliff on the opposite shore of Iwadatami. Ido is the name of this location, and Hagure means a place that easily collapses and is dangerous.

Completed in 1914, this is the longest bridge along the tracks of the Chichibu railroad. It is made from granite and brick. Although some parts of its are now reinforced with concrete, the bridge is still in service.

When the Chichibu railroad was extended to Chichibu, the shore to the left of Arakawa River ahead of Kami-Nagatoro Station had been a nanjaku jiban (soft ground) made of jamongan (serpentine), making it necessary to change routes. Thus, this bridge was built to cross over to the right shore of Arakawa River and connect to the Chichibu area.

This is an observatory with a panoramic view in all directions. It is a superb spot commanding a sweeping view of the Chichibu Basin and the mountains surrounding the basin. The area near the summit of Minoyama is turned into park. Minoyama is the only tandokuho (single mountain ridge) of Chichibu, and it is a mountain of henseigan (metamorphic rock) that separates the east side of Chichibu Basin.

It is a famous sightseeing spot for cherry blossoms, and many kinds of flowers can be enjoyed each season. The night view is also gorgeous, and the spot has been selected as one of the 100 Best Night View Spots in Japan. In recent years, it has grown popular as a viewing spot of sea of clouds, and during the season of sea of clouds many photographers visit from early morning.

Mount Hodo is a mountain with an elevation of 497m located on the north side of Chichibu Basin and overlooks the Chichibu Basin and Chichibu mountain range. At the summit there is a rear shrine located at the back of Hodosan Shrine. Visitors are able to access the summit on a ropeway.

The observatory is also one of Kanto’s largest planting areas of Japanese allspice which flowers in February. Different flowers can be enjoyed each season, and there is also a small animal park that is popular with children.

Mount Happu is a mountain with an elevation of 626.5m on the border of Minano, Chichibu District and Chichibu City. There are open vistas in each location and many hiking trails. It has gained popularity as a mountain where even beginners can enjoy climbing. It has also been selected for the 8 Best Views in Chichibu.