Stop 1: Mauna Ulu Lava Shield
Between 1969 and 1974, there were some spectacular eruptions from the Mauna Ulu vent. Eventually, a classic example of a lava shield was formed that is now over 120 meters above the pre-eruption surface. Today, Mauna Ulu makes a fascinating place to visit -- you can even walk to the summit and get back to the car in about 3 hours!
This is a general view of the shallow slopes of Mauna Ulu. Notice the very shallow "shield shape" of this cone. Just a few areas of older flows were left unaffected by this eruption; this is where the trees can still be found.
We saw a neat view of this type of landscape in Aerial Location No. 1a . This is an example of a tree mold, which formed when highly fluid lava from Mauna Ulu ran through part of the rain forest. However, because the lava was so fluid, and the regional slope so steep, the lava all drained away down hill. Because the trees chilled parts of the lava close to the ground, a casing of lava formed around the tree, that was then burnt away by the intense heat. The black and white ruler, marked in 5 cm intervals, shows the scale.
Two interesting things that this tree mold shows us is that the top of the mold is the former level of the lava flow (which was once over a meter deep here). Secondly, the direction of flow of the lava (which we can tell from the "tail" of lava leading off to the right) which was from left to right. Such observations help scientists learn much about what was going on during the eruption, even though the lava flow has changed dramatically during the intervening time.
BE CAREFUL HERE! At the summit of Mauna Ulu, there is a vertical drop of over 150 meters to the floor of the crater. There's no way out, so make sure you don't get too close! But if you do peer over the rim, you get these wonderful "out of this world" views. Notice the photographer (the P.I.'s dad, once again!) on the far rim for scale.
Towards the end of the Mauna Ulu eruptions in 1974, there were some high-volume eruptions that carved lava channels in the pre- existing flanks of the volcano. This is one of the fine examples that you can easily walk down on the northern flank of the shield.
From here you can continue on to Stop 2 on the ground, or you can pick another point from the Chain of Craters Virtual Field Trip page.
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Author: Peter Mouginis-Mark
Copyright by P. Mouginis-Mark
Curator: Lori Glaze