Mt. Jefferson formed after two explosions. The first explosion made a volcano higher than the Mt. Jefferson now!!! But since glaciers have been rubbing up against it, they have carved canyons into the volcano. When the volcano erupted again, it's summit fell and produced ash flows. The most recent eruption (which was September 30, 2000) probably occured when there were glaciers on Mt. Jefferson.Volcanoes that have
On this volcano the lava patterns are differnet to alot of the other volcanoes. Instead of the lava flowing out or blowing up, it just kind of pilwes up on top of each other. Volcanoligists think that this happened because of the glaciers rubing up against it. So when the lava flows out, it falls into the canyons and kind of pile up. The lava flow also looks glassy and has unusual joints. This is a result of contact with ice.
Another volcano is found i none of the Hawiian Islands. The island of Oahu is made up of two volcanoes. The oldest volcano is called Waianae, makes up the west part of the island. Waianae is a sheild volcano, it was formed about 2.95 to 3.8 million years ago. In the center of the volcano is a caldera, and the rift zomes extend to the northwest. Volcanoligists found rocks fosrm hte renewed volcanism stage, but they haven't been dated on how old they are yet. This volcano has been modified by erosion. The other volcano is named Koolau, which makes up the east part of the island.
Koolau is a large basaltic volcano that makes up the east part of the island. This volcano is also a sheild volcano, but the main sheild is about 1.8 to 2.7 million years old. It's caldera is located just south of Kaneohe Bay. There are alot of marks that locate the area of the riuft zone that trends to the northwest. Most of the volcano was eroded on purpose so they could show mhtre dikes. They also haven't found any of the rocks from the capping stage yet. Some of Hawaii's famous landmarks are from when the volcano splatter some of it's lava, cinder cone volcanoes that came from the renewed volcano. They believe that these landmarks were formed around 10,000 years ago or even 1 million years ago. Much of this volcano was broken of from a large landslide.