Friday, August 1, 2008

Day 169 (Sunday July 27). The Puna Coast

Today I went to the southeast side of the island, on what is called the Puna Coast. On the distance I had some nice views of huge steam clouds at both Pu’u O’o (the vent along the side of Kilauea) and Kalapana (where the lava is entering the ocean).

The highlight of the day was going over the series of fault scarps, or pali, that are the crown scarps of gigantic slide blocks that have downdropped the southeastern flank of Kilauea volcano into the ocean. This sliding must have happened several thousands of years ago (maybe 25,000 years ago?), because the scarps are mantled or draped over by innumerable lava flows.

A repeat of such landsliding would be of great concern to all the inhabitants of the Pacific rim, because the sudden volume change in the ocean basin would almost certainly trigger a train of devastating tsunami waves. One could regard it as Hawaii’s revenge on all those tsunami waves that have battered it from the Aleutians, Japan, and Chile. Before crying doomsday, however, one should keep in mind that the southeast flank of Kilauea is being buttressed by a growing submarine volcano, Loihi, which currently is still 3,000 ft under sea level. Or could it be the added weight of Loihi that caused the massive landsliding to begin with?

I enjoyed myself enormously looking at the fault scarps, and for once thought that maybe Hawaiian geology is not as boring as I had first imagined.

Down in the plain formed by the lavas that spilled down over the pali is an interesting archaeologic site. For no reason that was obvious to me, this site has been selected by the native Hawaiians as a “family record”. Over generations some families have selected an area, and have carved in the rock small hollows where the umbilical cord of newborns is deposited (I imagine to be eaten by the birds). And since they were there, and probably found time heavy, over the years they added designs and graffiti that now amount to a nice set of petroglyphs.

I finished the day with a visit to the East Rift Zone of Kilauea. I may have mentioned that Hawaiian volcanoes have the shape of an enormous croissant, and that under their immense weight they slowly spread out, tearing themselves apart. These tears, or rift zones, follow the “horns” of the croissant, and it is along them that most eruptions take place. To take the analogy one step further, imagine that you pour warm honey on the horn of a croissant; the honey would flow down at right angles from the length of the croissant, along the steepest slope. This is exactly what lava flows do in Hawaiian volcanoes, so the vent is on the rift zone—like Pu’u O’o—but the lava flow finds the shortest and steepest way to the ocean—like in Kalapana.

Nobody can get to Pu’u O’o without authorization, but I was able to visit its older sister, Mauna Ulu, which fed extensive lava flows in the 1970’s. Despite the 40 years elapsed, the ground around Mauna Ulu is still a desert, the lava flows are barren of all vegetation, and Mauna Ulu itself is surrounded by steam vents. A great place to imagine oneself in a barren moonscape.

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