Chichibu Geopark

Rocks of Sotochichibu Mountains and a large fault that runs between strata of Chichibu Basin can be observed. This location is said to be the remains of an ancient copper mine.

Copper found in Chichibu was presented to the imperial court and Japan’s first currency in circulation “Wadokaichin” was made. Hijiri Shrine located here enshrines a god of money and is a popular power spot.

At the inner shrine, you can see a discordance of the jamongan (serpentine) of Sotochichibu Mountains and the conglomerate bedding of Chichibu Basin. Between the two strata there is a difference in time of roughly 70 million to 50 million years.

About 1,300 or more stone buddha statues are made from stones sourced from the western corner of Chichibu Basin and these stones were carried to this location by the hands of many worshipers.

The huge rock on which the Kannon-do is erected is a sandstone breccia, which flowed in from Sotochichibu Mountains (3km away to the east) that was elevated approximately 16 million years ago. On a rock in the precincts is a pothole that was made when this location used to be the riverbed of Arakawa River.

There is a folklore that, long ago, in a year when there was a severe drought, a monk from the early 9th century called Kobo Daishi (also known as Kukai) sent prayers, and as a result, the rock was split and a dragon appeared that made heavy rain fall on the village and saved the people from hunger.

The low terraces where the city area is spread out is a relatively new terrace that is said to have been a dry riverbed since around 70,000 years ago. In the past, there was a lot of gushing spring flowing in from the terrace.

These seven wells are said to have come from the gushing spring on the main street, which was used when moving Myoken Bosatsu (one of the gods of Chichibu Shrine) from the location where it was enshrined in around 1320 and earlier to the current location of the Chichibu Shrine.

Hitsujiyama Park is on top of a middle terrace created by Arakawa River, and from the top of the Miharashi-no-Oka you can overlook the entire Chichibu City.

This area started to be called Hitsujiyama (literally means “sheep mountain” in Japanese) because it was where sheep were bred prior to the war. In recent years, it has served as a place of recreation and relaxation of citizens that has become famous for the Shibazakura-no-Oka (hill of moss phlox).

Odamaki Hill, where Chichibu Muse Park is located, is the oldest of the river terraces created by Arakawa River, and it is a high terrace that was formed approximately 500,000 years in the past. Both Odamaki Hill and Hitsujiyama Hill are flat on the top. This is because they used to be riverbeds of Arakawa River.

In recent years, the observatory has gained popularity as one of the photo spots of Chichibu’s sea of clouds.

This is a rock cliff made of limestone located on the western edge of Mount Buko. Coral reef that had grown in the volcanic zone of the South Sea approximately 200 million years in the past had attached to the side of the continental tectonic plate due to movements of the oceanic plate of the Pacific Ocean. After repeated movements, bulging, and erosion of the tectonic plate, the coral reef changed form into its current appearance.

The “Iwakage Ruins” located below the rock cliff was where ancient people lived since the beginning of the Jomon period. Hashidate-do Temple (the 28th temple of the Chichibu 34 Kannon Pilgrimage) is located against the backdrop of this rock cliff.

Hashidate Shonyudo is the only tourist cave in the prefecture and it has a rare vertical shape.

You can see the stratum back from the time when Kochichibuwan (Paleo Chichibu Bay)—which existed in the area of the current Chichibu Basin from roughly 17 million to 15 million years ago—ceased to exist. The conglomerate outcrop is designated as a national natural monument.

When the Sotochichibu Mountains bulged out, and the part that is now the Chichibu Basin settled, the cliffs surrounding the sea had collapsed and accumulated on the eastern edge of the basin. This outcrop had been deposited right after the cliffs had been worn away, so there are still huge rock bodies with a horny shape.

This is one of the Hino faults, which have formed on the border between the Chichibu Mountains and Chichibu Basin. The cave was created as a result of water washing away the portion of the rock that had crumbled due to a shift in the fault. It is called a “fault cave.”

There is a place called Kagamihada (slickenside) that had been polished when the faults shifted and rubbed against each other, and you can also see linear scratches. It is rare to find a place where you can directly observe a fault plane.

In the past, manganese contained in chert of the Chichibu belt had been mined in the Chichibu Mountains.

The largest manganese mine was located in Minano Town, but the mine here can be visited relatively safely.

Tamagomizu (literally means “egg water” in Japanese) is a spring water that smells of sulfur, and it is one of the multiple sulfur fountains located along the faults around Chichibu Basin. People in the past are said to have drank the water for curing or mixed it in their bath.

The large katsura tree of Myogasasu located on the mountain stream of Anyagawa River is one of the largest katsura trees in Saitama Prefecture with a circumference of 11m and height of 30m, and the tree is said to be around 450 years old.

This spot, which is located at the entrance of Otaki District of Chichibu City, forms a rugged terrain consisting of limestone body scattered on the hard stratum of Chichibu belt, and it blocks the passage of people. Here, there is also a hand-drilled tunnel, in which people drilled the limestone body at the end of the 19th century.

The large tunnel is roughly 40m in length and 4.8m in height, and it played an important role as a pilgrimage route to Mitsumine Jinja until a national highway (the current Japan National Route 140) was made in 1921.

This is a cave in a rock wall made of limestone, and the cave was formed through erosion caused by water flowing from Arakawa River about 50,000 years ago.

People migrated and lived here since the Jomon period (around 8,000 B.C. to 300 B.C.), and the location is said to have been used as a habitat as well as a hunting camp. Many earthenware and bones of animals have been excavated here.

Chichibu Tonalite is a type of igneous rock that was crystallized and formed deep underground. Magma that had risen from deep underground came into contact with limestone bodies on the Chichibu belt, and this resulted in the Chichibu mine deposit (skarn deposit).

The history of mining operations dates back to the middle ages. One of the people who dreamt of making a fortune at a stroke in this location was Gennai Hiraga, an inventor of the Edo period. Since the 20th century, mining operations were modernized, and reached its heyday in the 1960s. The location became a prosperous mining town where approximately two thousand and several hundred people lived.

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 a beautiful waterfall that is approximately 13m both in height and width. The rock cliff where the waterfall is located is an exposure of a sandy mudstone that had been deposited on the sea bed of Paleo Chichibu Bay, which existed 15 million years ago.

This is a park developed on top of a bedrock of white sandstone, which is a coarse sandstone made of rock deposits from the early period of the formation of Paleo Chichibu Bay. The view from the top of the rocky mountain is superb.

You can enjoy approximately 5,000 Katakuri (Dogtooth violet) flowers that have been planted in the park while taking a stroll through the promenade every year between late March and mid-April.

You can see the stratum from the time when Paleo Chichibu Bay, which existed about 17 million to 15 million years ago, was still a deep sea. A dynamic stratum is exposed over a width of approximately 800m, showing proof to the present that this location was submerged in the deep sea in the past. It is designated as a national natural monument.

You can observe a twisted stratum that was formed through landslides at the bottom of the sea (folds), a time difference between strata (discordance), and a stratum created over a long period of time on the sea bed through sand and mud (turbidite) that has a distinct striped pattern.

When this area was still submerged in the sea, a slope was formed on the sea bed due to the bulging of mountains, and the sediments on the sea bed that had not solidified yet slid down due to earthquakes, resulting in a curved strata (slump fold) that can be observed here.

You can see the stratum when Paleo Chichibu Bay, which existed about 17 million to 15 million years ago, was still a shallow sea. Many fossils have been excavated in this location giving testament to the fact that this was a rich habitat of marine creatures back when it was part of the sea. Yobake is a large outcrop that is representative of Chichibu, and it has been designated as a national natural monument and selected for the Geology 100 Selection of Japan.

“Yo” of Yobake refers to “Taiyo” or sun, and “bake” refers to “gake” or cliff in Chichibu. Yobake thus has the meaning of “cliff shone under the sun,” and this is how local people called it since the past.

On the back of the temple dedicated to Kannon, there is a mysterious cave with many holes in it like a bee nest. This is caused by a weathering phenomenon called Tafoni, in which the salts in the rock seep into the surface, crystallize, and then break the surface of the rock.

Ofuneiwa (literally means “boat rock” in Japanese) is a large sandstone on a precipitous cliff that is protruding like the bow of a boat. At the tip of this rock is enshrined Ofune Kannon (“boat Kannon”). This is an excellent sightseeing spot where you can overlook the entire Chichibu Basin.

The large rock cliff around the temple dedicated to Kannon is a sandstone deposited on the sea bed around 17 million years ago when the Chichibu Basin caved in and the ocean began to cover the region. On the rock face next to Seijo Falls, which has a height of 30m falling from the rock cliff, there is a small Buddha figure carved on a rock surface.

At the temple gate is a monolithic Stone Nio Guardian that is the largest of its kind in Japan. This statue and other stone Buddhas and stone walls are made from the so-called “Iwadono Sawaishi” or local tuffaceous sandstone. This is a stone material that has been used in various locations of the Chichibu region from long ago.

You can observe a discordance where the stratum from the ocean from around 100 million years ago during the age of dinosaurs, and the stratum created in the sea bed when Paleo Chichibu Bay came into existence during the age of mammals, come into contact after a period of roughly 100 million years. The discordance is designated as a national natural monument.

The valley where Minamotozawa is located in a region with an extended stratum that was deposited approximately 130 million to 100 million years in the past during the age of dinosaurs. Kenji Miyazawa, who is a prominent Japanese poet and a writer of children’s literature, visited this place during his geological excursion in Chichibu in 1916.

This is a rocky mountain made of limestone on the Chichibu belt with two steep summits. Just like Chichibu’s landmark “Mount Buko,” it was born from the South Sea far away and moved on top of an oceanic plate that pushed it against the continent. Fossils have been found here such as of fusulina and sea lily.

It is famous as a full-scale rock climbing location that is easy to access from the Tokyo metropolitan area, and many hikers visit during the hiking season.

This is a stunning waterfall that falls from the mountain stream flowing from Mount Ryokami, which is a mountain that looks like a saw that towers on the west side of Chichibu Basin and is made of a large chert rock body. It is the only waterfall in Saitama Prefecture selected for Japan’s Top 100 Waterfalls.