The Rocks that make up the Tedori River Basin

If you look at the various stones at the side of the river, you can get an idea of what kind of rocks the land is made of. Take a look at, and touch real samples of rocks taken from different areas around the Hakusan Tedorigawa Geopark.

Memories of Fossicking for Pebbles (Diorama)

From long ago, the children who lived here have fond memories of searching for pebbles by the river and beach. Prized, shiny white pebbles, called orthoquartzite, can be found throughout the river, and even by the beach at the river mouth. In this diorama you can see the memory of a man who spent many hours of his childhood by the river, searching for pretty stones with his friends. If you understand Japanese, you can listen to his story, or just listen to hear the emotion in his voice, as he talks about his distant past.

Orthoquartzite

(Japanese: tama ishi)
Orthoquartzite is a kind of sandstone, made up of many small grains of quartz welded together. The pebbles are pieces of orthoquortzite that have broken off and been eroded into round shapes. Large orthoquartzite bodies cannot be found anywhere within Japan, and are only found deep in the interior of continental landforms. So where did these rocks come from? 

At the time these orthoquartzite pebbles were created, Japan was connected to the Eurasian plate to the west (current China). The stone was eroded from a large body of orthoquartzite, and eroded into pebbles as it travelled down a river. These pebbles deposited by the river, and over time turned into a bed of conglomerate (sandstone mixed with pebbles). 

Following this, the Japanese archipelago split from the continent, and began forming current Japan. The conglomerate containing pebbles of orthoquartzite became part of a series of tall mountains, from which rivers formed. As the conglomerate eroded, these pebbles dropped out, and moved downstream to where we find them today. It is rocks like these that provide evidence that Japan was connected to the continent during the time of the dinosaurs.