Hawaiian Volcanoes and the Geological Make-up
...e volcanoes have effected the island of Hawaii we need to look at how the creation of these volcanoes and the formation stages that have effected the Hawaiian Islands. The first natural event to take place is the initial stage of development. This is the stage where the pillow lava is formed by small fissures that are open on the sea floor. Volcanoes grow by adding layer upon layer of new pillow lava. (SITE 4). Most of the Hawaiian Volcanoes are shield volcanoes, and the lava is theoleiitic in composition. (SITE 4). These volcanoes are considered shield volcanoes due to the frequent eruptions. Under deep ocean conditions, the weight of the overlying water does not allow the heat of the lava to generate steam. Lava erupts and forms pillows making the slopes of these volcanoes very steep(SITE4). Mahukona, (“leeward steam”), was the first volcano to grow above sea level to form the Island of Hawaii. The period of active landsliding occurs near the end of the shield-building stage because the volcano is growing at a rapid rate and has obtained its greatest height, producing steep slopes and maximum instability. Due to the steep slopes generated by the Hawaiian Volcanoes, geologists have discovered about 70 major landslides that cover half of the flanks of Hawaii. (SITE 5). These landslides are among the largest on the earth attaining lengths of 125 miles long and volumes of 1200 cubic miles. After the formation of these massive landslides, capping is the next natural phenomenon to occur. Alkalic basalts fill caldras and produce a steep slide cap. During the capping stage explosive eruptions occur more frequently than in the shield-building stage. Time between the eruptions gradually increase, and eventually eruptions stop. Scientists have discovered that the Hualalai Volcano is in the capping stage (there are numerous cones and craters near the summit of the volcano). Scientist say about twenty percent of the volcano has been covered by lava in the last 1,ooo years. (SITE 6). Another volcano to have started the capping stage is the Mauna Kea volcano. The lower flanks of this volcano have not been affected by lava flows for 10,000 years. Scientists figured the eruption of the upper slopes of the volcano was 3,5000 years ago, and between 5,000 and 3,000 years ago 20 percent of the upper slopes were covered by lava. (SITE 6) The next event to occur which is one of the most important when compared to the movement of the Hawaiian Islands. Movement of the Pacific Plate has carried the islands 1,4000 miles northwest of the Hawaiiam hot spot. The islands have eroded down close to sea level and are surrounded by coral reef.(SITE 7) This is basic terms means that Erosion reduces the height of ...