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I don't know what to say about Hanauma Bay. It seems to have undergone dramatic changes in the past 20 years, and yet to someone who hasn't seen it for 20 years, the changes are barely noticeable. Apparently some years ago, the ecological impact of tourism nearly killed the reef and polluted the waters to a degree that it was virtually unswimmable. To reduce the number of visitors, authorities have over the years instituted a variety of programs, from limiting parking to closing the bay on certain days. At various times, a fee has been exacted for every body entering the park. If you are wondering about the lack of bodies the picture above, the reason is the bay closed at something like 4:30 in the afternoon and we were among the last out -- another measure to reduce visitor impact. A semi-permanent display provides a disturbing glimpse of past problems, but also offers advice on how visitors can help the bay recover, such as by not walking on the reef.

At the moment, it appears that the bay is recovering quite nicely, thank you. The water was reasonably clear, but a bit silty, and there were few fish, even beyond the reef. Certainly there were none of the swarms of multi-colored fish that I remember from past years of snorkeling here.

  Hanauma Bay was formed from a volcanic strucutre called a tuff cone. (Tuff is consolidated volcanic ash.) The bay actually consists of at least two overlapping cones which were formed during the Honolulu Volcanic Series, which also includes Koko Head (to the right side of Hanauma Bay), Koko Crater (to the northeast, and Rabbit Island (off Makapuu) among several others. This chain of cones (the Koko fissure) forms the southwest corner of O'ahu. The bay itself was created when one wall of the most seaward cone collapsed. In the QuickTime panoramic movie above you can see this opening. (Click and hold down your computer's mouse button over the picture, then scroll right or left. You can also use your keyboard's arrow keys, though this results in a jerky motion. Use your Shift key to zoom in on the bench, your Control key to zoom out). This bench becomes important later in this story.)

In the panoramic movie above, you can pan left and right using your mouse (click-drag) and zoom in using your shift and control keys.

Also note the wave-cut platform, or bench, of dark lava that runs along both sides of the bay. This bench was created when the ocean was about 5 feet higher than it is today.

In the meantime, here are some family pictures....


Okay, remember that bench we were talking about earlier? We are now walking along the bench on the left-hand side of the bay, heading towards the point. In rough seas, this can be a quite dangerous walk, since waves can unexpectly crash over the bench and wash the unwary away. Even on relatively calm days, walkers can get wet.

See that bluff in the background, on the other side of the bay? It's several tens of meters high, but I've seen waves send spray up and well over the TOP.

The tuff that comprises the Hanauma Bay cones is relatively soft and easily eroded by wave action, resulting in all kinds of odd structures, including this small arch.

But the most interesting structure of all is the channel that lies just berfore the mouth of the bay on the right side. (See picture at right.)

(Photo from Virtually Hawaii, a virtually guided tour of the islands. Well done and highly recommended!)

The long channel funnels waves under the rocks at the back of the channel, and the water is forced up through a deep and wide open pit. The action is very much like that of a common bathroom facility, hence the popular name for this geologic structure, the Toilet Bowl.

Although it looks dangerous, people like to jump into the pit and ride the water as it moves up and down in the bowl. (The bottom is sandy.) On good days, the water drains completely, then, with a rush and a whoose, comes charging back in, filling and overflowing the bowl. The ride is better than anything Disney has come up with.

Some people, my brothers, for example, have even gone out into the channel with the escaping water, then ridden the returning wave back under the rocks and into the bowl. That's something I could never work up the nerve to try.

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