Geologically, a high island or volcanic island is an island of volcanic origin. The term can be used to distinguish such islands from low islands, which are formed from sedimentation or the uplifting of coral reefs (which have often formed on sunken volcanos).
Primary waves, or P waves. Correct me if wrong
Yes, the capital of a state or country is that state/country's capital city. Santiago is Chile's capital city. For example, the capital of the United States is Washington D.C., which is a city.
