Answer: a few islands that were formed millions of years ago by volcanic activity
Japan is an island nation, it is a stratovolcanic archipelago composed of about 1,042 islands, and more than 2,000 islets that extend along the east Asian coast of the Pacific Ocean.
This country is located in one of the geologically most unstable and complex areas of the Earth: the Pacific Ring of Fire, therefore it is a highly seismic zone.