Monday, June 1, 2009

The Return of the Airliner Chronicles: the Biggest Mountains on the Planet


Back in the dark ages of 18 months ago, I ran a series of blogs on the theme of photography from the "perfect" photo medium of a scratchy glare-filled airliner window. Sometimes one can get lucky and get some decent geological perspectives, and of course, sometimes not! After grouching this morning about lousy airport experiences, we made it onto the plane, and for the first time in five tries I was sitting on the correct side of the plane to get a view of the islands as we made our final approach to Honolulu. So the airliner chronicles return!

The top picture shows three of the biggest and tallest mountains on the planet. From left to right they are Mauna Kea and Mauna Loa on the Big Island of Hawai'i, and Haleakala on the island of Maui. Tallest? Mauna Kea and Mauna Loa aren't quite 14,000 feet tall above sea level. But, they sit in 17,000 feet of ocean, and as such stand more than 30,000 from their base. And big? The gentle slopes of the volcanoes belie the sheer bulk of these mountains: some 10,000 cubic miles of rock make up the mass of Mauna Loa. With any luck, my students and I will "climb" to the summit of two of these mountains in the coming weeks.

The second photo is an iconic mountain from a different angle. It is Diamond Head, the tuff cone that overlooks Waikiki and Honolulu. Although the volcanoes making up the island of Oahu are long extinct (2.6 million years old), a series of minor eruptions 200,000 years ago produced a few cones along the coastal plains of the islands. Known to the original Hawaiians as Le Ahi, it got the current name from sailers in the 1800's who thought they had found the precious gems along the flanks of the cone. The sparkling crystals were actually calcite.

For what it is worth, Hawaii is rich in one gemstone: peridot. Known to geologists more commonly as olivine, it is a beautiful green mineral that is a main constituent of basalt, the volcanic rock that makes up most of the islands.