An archipelago (/ˌɑːrkɪˈpɛləɡoʊ/ ( listen) ARK-ih-PEL-ə-goh), sometimes called an island group or island chain, is a chain, cluster or collection of islands, or sometimes a sea containing a small number of scattered islands.
sea floor spreading- the formation of new areas of oceanic crust, which occurs through the upwelling of magma at midocean ridges and its subsequent outward movement on either side.
A fault is a fracture along which the blocks of crust on either side have moved relative to one another parallel to the fracture. Strike-slip, normal, and reverse faults. A reverse fault with a small dip angle is called a thrust fault.