Geologic Map of Hawaii
(c) 2006 Andrew Alden, licensed to About.com, Inc. (fair use policy)
Hawaii is entirely built of young volcanoes, so this USGS map (I-1091-G, made in 1988) doesn't have much in the way of color. Basically, all of the islands are less than 10 million years old, with the Big Island the youngest and the oldest being Nihoa (which is part of the islands but not part of the state), off the map to the northwest. The color refers to the composition of the lava, the magenta and blue being basalt and the brown and green (just a smidgeon on Maui) being rocks higher in silica.
All of these islands are the product of a single source of hot material rising from the mantle—a hotspot. Whether that hotspot is a deep-seated plume of mantle material or a slow-growing crack in the Pacific plate is still being discussed. To the southeast of Hawaii island is a seamount named Loihi. Over the next hundred thousand years or so, it will emerge as Hawaii's newest island.
Most of the islands have irregular shapes, not like the round volcanoes you find on continents. This is because their sides tend to collapse in gigantic landslides, leaving chunks the size of cities scattered around the deep sea floor near Hawaii. If such a landslide happened today it would be devastating to the islands and, thanks to tsunamis, the entire coast of the Pacific Ocean.
All the details are visible on the 2100x1400 pixel version (250 KB) or the giant version at 5000x3300 pixels (1 MB).
More Hawaii resources on About.com:
Hawaii Travel
Hawaii Maps
Hawaii Geography, State Symbols & Facts
Hawaii Campgrounds
Hawaii Farmers Markets
Hawaii Fishing
Hawaii National Parks
Hawaii Archaeology
Back to Geologic Maps of the States
