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Iao Needle is a giant ridge over 400 meters high. It marks the path of a nearly vertical dike. Dikes form deep within volcanoes along lines of weakness. As erosion proceeds, the dikes become exposed at the surface. Because the rocks that formed the dike cooled very slowly, it is more massive and is more difficult to erode than the surrounding lava flows.
Standing at the visitors' overlook for Iao Needle, one can look around the inside of the old West Maui caldera (pictures above and below). Many old lava flows are exposed in the walls making this site of interest to geologists, but it is the spectacular scenery with lush vegetation and peaks shrouded in clouds that make this area so attractive for visitors!
From here you can continue on to Stop 2.
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Maui Virtual Field Trip]