The Natsudomari Peninsula (Japanese: 夏泊半島, Hepburn: Natsudomari-hantō) is a peninsula on the northern end of the Japanese island, Honshū, that stretches north into Mutsu Bay.

[2] The peninsula is notably an attractive nesting place for Siberian tundra swan.

[4] The second oldest rock is a mixture of Late Jurassic chert and limestone known as the Tateishi Formation.

These layers include andesite, tuff breccia, and a system of sills and dikes left over from an extinct volcano that was centered at Mount Sasamori, a foothill of Mount Mizugasawa.

Layers from the Quaternary are mainly made up of sedimentary deposits and tephra from Mount Iwaki.