ITOIGAWA, Niigata Prefecture--Visitors to a geological park here can now get a clearer view of a giant fault line’s outcrop, which defines the geological boundary between the eastern and western parts of the Japanese archipelago, after a refurbishment.

The outcrop of the Itoigawa-Shizuoka Tectonic Line has been available for public viewing since Aug. 2 at Fossa Magna Park in the Negoya district of Itoigawa.

The city government is hoping to attract more visitors to the revamped park, which it defines as one of the core component sites of the Itoigawa UNESCO Global Geopark.

Fossa Magna Park is a scientific tour site for viewing a geological fault, where part of the Itoigawa-Shizuoka Tectonic Line has been exposed artificially. Rock on the eastern side, about 16 million years old, abuts older rock on the western side, which is 300 to 400 million years old.

The fault is believed to define a boundary between two tectonic plates, each about 100 kilometers thick: the North American plate on the east and the Eurasian plate on the west.

Fossa Magna Park was opened in fiscal 1990. The outcrop was initially covered with a stone wall to prevent landslides, prompting some visitors to complain they could not make out the location of the fault very easily.

The stone wall was removed during the latest facelift after alternative work was done to block landslides.

As a result, the fault line, which was previously visible only over a stretch of three to four meters, is now clearly observable over more than 15 meters.

The work cost 148 million yen ($1.34 million).

Fossa Magna, which means “great ditch” in Latin, was discovered and named by Edmund Naumann, a German geologist who came to Japan in the Meiji Era (1868-1912). It is believed to represent a fissure formed in the earth when the Japanese islands separated from the Asian continent.

The Itoigawa-Shizuoka Tectonic Line, a fault running along the western border of Fossa Magna, defines a geological boundary between eastern and western Japan.

Fossa Magna is believed to be bordered on the east by the Shibata-Koide Tectonic Line and the Kashiwazaki-Chiba Tectonic Line.