All of the Hawaiian islands were formed by volcanoes, as the tectonic plate for this part of the world moved Northwest over a hot spot in the earth's crust. This is also how the Big Island was formed. Kilauea volcano on the Big Island is a shield volcano, meaning that it's built up thin layer on top of thin layer. |
Kilauea is adding new land to the Big Island even now, as lava hits the ocean, turning the water to steam. |
The water around Hawaii is extremely deep, and the lava isn't very strong, so the new ledges which are created often collapse. If you look closely, you can see dark cracks running across some of the light colored sections on the right of this photo. Sometimes an area the size of several city blocks will collapse underwater, and people viewing the lava flows have been killed in this way. |
Lava can sometimes be seen flowing down towards the ocean. The ledge here is about 30 or 40 feet high. |
In places you can see the lava actually flowing into the ocean. |