It sits northwest of Tokyo Bay, in the southwest of the plain.

The Tama River carved the Okutama Mountains and deposited a large alluvial fan that spread out from Ōme.

[1] The fan is the base layer of the Musashino Plateau, and is covered by the Kantō Loam Formation, which is 5 to 15 meters thick.

The loam is primarily andesite or basaltic sandy mud formed from volcanic ash that the wind carried west from Mount Fuji.

The other is in the north and is thought to be a remnant of the former Tama River channel.