This is an image the ocean floor of the Earth, showing islands being formed.
Click on image for full size
Image from: NOAA/NESDIS/National Geophysical Data Center, Boulder, CO
Island Arc Formation
There are two ways in which islands can form. 1.) As a slab of crust is being forced down into the Earth, it melts. Hot, melted material rises again into the crust, forming a series of volcanoes. These volcanoes can make a chain of islands called an "island arc". Examples of island arcs are the Aleutian Islands of Alaska, shown here.
2.) The second way in which islands are formed is when there are hot spots in the lithosphere. Hawaii is an example of this type of island formation.
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