Southeast Oahu Ground Tour
Stop 1: The View From Tantalus
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One of the most spectacular recent eruptions on Oahu took place about 70,000 years ago on one part of the Koolau Range just outside of where Honolulu is now located. This site combines the peaks of Round Top, Sugar Loaf, and Tantalus (see also the view of this area from Diamond Head, which is Stop #2 on this Virtual Field Trip). There is a great road around this area that is an easy, hour-long, drive that provides some fine views of Waikiki and the products of this eruption. Here are a few examples.
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On the road around Tantalus, we get an excellent view of Manoa Valley (in the foreground), the part of Honolulu called Kaimuki, and on the horizon the world famous Diamond Head.
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The large fire fountain eruption that took place on Tantalus deposited several meters of ash on the edge of Manoa Valley. Part of this ash deposit can be seen here. This same eruption produced a 10 meter-thick lava flow that entered Manoa Valley. This flow had great econonmic value in the early 20th century, as the dense lava was quarried for building stone to be used in the rapidly growing city of Honolulu.
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The deposits formed by the eruption on Tantalus are just a few of the features that can be seen from within Manoa Valley. Here we are looking from the valley floor to the place where photos #1 and #2 were taken. From this perspective, the older lava flows associated with the formation of the Koolau volcano can be seen as a series of gently dipping (from top right to bottom left) layers in the valley wall.
From here you can continue on to Stop 2 on the ground.
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Southeast Oahu Virtual Field Trip
Author: Peter Mouginis-Mark
Copyright by P. Mouginis-Mark
Curator: Lori Glaze