Scripps Institution of Oceanography, UCSD
Volcano Expedition to the Marianas

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April 2004
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Daily Journal

Day 1 | April 9, 2004

The Caroline Islands

Columnar Basalt in Chuuk

Columnar basalts in Nan Madol

En route to the Mariana Islands, Alison, Lillie and I (Dave) took the slow route via Hawaii, the Marshall and Caroline islands. We stayed two days each on Pohnpei and Chuuk in Micronesia to sample lavas. Both islands are volcanic in origin and are surrounded by coral reefs. We will use the same analytical techniques on these lavas as we plan for the Mariana rocks. In this case, we will characterize the volatile features of volcanoes erupted within tectonic plates as opposed to at plate boundaries like the Mariana volcanoes.

On Pohnpei, we collected olivine-bearing lavas from a number of sites around the island. We hope to test one of the current controversies regarding the origin of intra-plate volcanoes: whether they come from deep in the mantle via plumes or if they form by cracking of the plates. An unexpected thrill, however, was the opportunity to visit Nan Madol, an island kingdom started in the seventh century. The complex is constructed of columnar basalts interwoven much like a log cabin . Columnar basalts form during the slow cooling of massive lava flows. These columns were used as the foundation to form about 80 islands, as well as various structures on the islands and the protecting sea walls. We entered by boat at high tide and came upon Nan Dowas - a spectacular war temple. Further excavation in the complex will surely reveal more treasures.

Columnar Basalts

Columnar basalt in cliff

We discovered more columnar basalts on Chuuk, and in this case we were able to sample them. Chuuk is best known for its underwater graveyard of Japanese ships sunk during a two-day bombing raid by the Americans in World War II. Tomorrow (Saturday), we will explore these wrecks before taking off for Saipan where we will meet the rest of the expedition team.