Yokokawa no jaishi

Yokokawa no jaishi is a geological formation featuring magmatic dikes made of diorite rock that rise from the mountainous landscape of Nagano Prefecture. The visible rock layers reveal how molten material intruded into existing stone and created these distinctive striations and patterns across the surface.

The diorite dikes formed through ancient magmatic processes when molten rock pushed into and fractured existing stone layers deep underground. This geological activity shaped the landscape and structure of the Japanese islands over millions of years.

Local geological researchers and students frequently visit this designated natural monument to study the characteristics of magmatic dike formations in Japan.

The site sits in hilly terrain, so wear appropriate shoes for uneven ground and be prepared for steep sections. The best time to visit is during months with stable weather when mountain paths are easily walkable.

The dikes here display unusual fracture patterns in the rock that help scientists understand the tectonic forces that shaped this landscape. These patterns appear distinctly at only a few other locations across the region.

Location: Tatsuno

GPS coordinates: 35.97266,137.89824

Latest update: December 12, 2025 14:23