Tokachi Pyroclastic Flow Deposit (Welded tuff) at Hinode is deposit from an eruption of a volcano located at the centre of Hokkaido from 1.25 to 1.46 million years ago. The volcano used to exist on the northeast side of the Mt.Tokachidake.

Pyroclastic flow is composed of volcanic ash, rock fragments, and volcanic gas. It flows along the ground away from a volcano at high speed, and at high temperature. Gray cloud creeps onward along the earth unlike mudflow, and debris flow.

Pyroclastic flow is originally composed of soft substances such as pumice and volcanic ash. Tokachi Pyroclastic Flow Deposit is categorized as welded tuff. It has three processes. First of all, lava was melted due to magmatic heat immediately after eruptions. Second of all, there was the solidification of molten magma. Finally welded tuff was pressed from above the weight of itself, which made it hard.

Including much quartz is a characteristic of Tokachi Pyroclastic Flow Deposit. This quartz is large about 5mm in diameter, transparent or pink, and glistening.