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ChromaDepth
Section II: Parts of the United States
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The Hawaiian Islands
Description: The Hawaiian Islands sit in the middle of the Pacific Ocean and were formed from the lava of many volcanoes.
Things to Notice:
- We think of Hawaii as a chain of distinct islands, but without the water, we can see that Hawaii is really a single landmass formed where the lava flow from volcanoes merged together. The parts of Hawaii that we call “islands” are really just the portion of that big landmass that sticks above sea level.
- The islands are like a long tube with small areas sticking above the water. The islands are connected to each other below water like long jellyroll with few high areas sticking out of the water.
- This “jellyroll” is tilted to the northwest, with the highest part being the Big Island on the southeast. This is the youngest area, with the age increasing to the northwest. As islands get older, they become denser and sink, as they are riding above the fluid mantle.
- Islands generally get progressively smaller and lower to the northwest, as they are sinking.
- The newest Hawaiian Island volcano, named Loihi, is southeast of the Big Island, but is too small to reach the surface. But, in a few thousand years it will break through the ocean’s surface and will become another island.
- The Hawaiian Islands are the product of a hot spot of mantle material being injected to the surface, much like a stationary candle burning a hole through a napkin being moved over the candle flame. The burned holes and smokey napkin would show what direction the candle moved and how fast, assuming that the output
of the candle was uniform. This hotspot is beneath the Big Island right now and indicates that the outer surface of the Pacific plate is moving to the northeast.
- Hawaii is part of the Hawaiian-Emperor seamount chain, which goes all the way to Alaska. There is a big bend between the two parts, which is a record of when India ran into Asia and changed most of the world plate motions about 44 million years ago. (This is shown very clearly in the Pacific Rim image, which is
elsewhere in this exhibit).
- The Big Island has a three-pronged shape. This is because of the 120° angle that forms when breaking a rock (and most other things) in least-work geometry. The high elevations are where lava is being injected and then runs downhill into the ocean. Mauna Loa geometry shows up beautifully.
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