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This is an image the ocean floor of the Earth, showing islands being formed.
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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. s


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Traveling Nitrogen Classroom Activity Kit

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Subduction

When two sections of the Earth's crust collide, one slab of lithosphere can be forced back down into the deeper regions of the Earth, as shown in this picture. The slab that is forced back into the Earth...more

Volcano Formation

Volcanoes form when hot material from below rises and leaks into the crust. The hot material, called magma, rising from lower ground, gathers in a reservoir called the magma chamber. Eventually, but not...more

Plume Volcanism

This drawing shows another way that islands are made. A rising hot bubble of material finds it's way into the crust of the Earth from the deep interior, and begins to erupt. This bubble or "plume" is called...more

Volcanic Ash

Ash is formed as a volcano erupts when rocks made by the volcano blow apart into millions of tiny pieces. The rocks are still very hot, because they just formed from lava. If the hot rocks come into contact...more

Cinder Cones

Cinder cones are simple volcanoes which have a cone shape and are not very big. Compare the size of this volcano to the strato-volcano in this image. They are usually made of piles of lava, not ash. During...more

Flowing Lava

Lava can move in two ways, wide flat lava flows, or through channels which squeeze the lava into a small area. The fastest lava flows move at about 6 mi/hr, an easy jog, but they average between 2/3 and...more

How Do Plates Move?

Plates at our planetís surface move because heat in the Earthís core causes molten rock in the mantle layer to flow. We used to think the Earthís plates just surfed on top of the moving mantle, but now...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA