Consider the following statements about type of volcanoes:(1) Shield V...
The correct option is D.
Shield volcanoes are almost exclusively basalt, a type of lava that is very fluid when erupted. For this reason these volcanoes are not steep (you can't pile up a fluid that easily runs downhill).
Examples of shield volcanoes are Kilauea and Mauna Loa (and their Hawaiian friends), Fernandina (and its Galápagos friends), Karthala, Erta Ale, Tolbachik, Masaya, and many others. Here are 4 of the volcanoes that comprise the big island of Hawaii. They are Mauna Kea (MK), Mauna Loa (ML), Hualalai (H), and Kohala (K).
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Consider the following statements about type of volcanoes:(1) Shield V...
Explanation:
Statement 1: Shield Volcanoes are mostly made up of Basalt
Shield volcanoes are indeed mostly made up of basalt. Basalt is a type of igneous rock that is low in silica content and has a low viscosity. This low viscosity allows the lava to flow easily and spread out in thin, broad sheets. As a result, shield volcanoes have a broad, gently sloping shape resembling a shield or a warrior's shield, hence the name. Basaltic lava also has a relatively low gas content, which further contributes to the gentle eruptions and the formation of shield volcanoes.
Statement 2: Hawaiian Volcanoes are examples of Shield Volcanoes
This statement is correct. Hawaiian volcanoes, such as Mauna Loa and Kilauea, are classic examples of shield volcanoes. These volcanoes have a low profile and are characterized by their broad, gently sloping sides. The eruptions of Hawaiian volcanoes are typically effusive, meaning that lava flows out of the volcano relatively peacefully and spreads out in thin, broad sheets. These eruptions are often accompanied by the formation of lava fountains and lava lakes.
Statement 3: Composite volcanoes are characterized by eruptions of cooler and more viscous lavas than basalt
This statement is also correct. Composite volcanoes, also known as stratovolcanoes, are characterized by eruptions of cooler and more viscous lavas compared to basalt. These lavas have a higher silica content, which increases their viscosity. As a result, the lava does not flow as easily and tends to accumulate near the vent, leading to the formation of steep-sided volcanoes with a conical shape. Composite volcanoes are typically associated with explosive eruptions, as the thick lava traps gases, leading to build-up of pressure and explosive release.
Conclusion
All three statements are correct. Shield volcanoes are indeed mostly made up of basalt, Hawaiian volcanoes are examples of shield volcanoes, and composite volcanoes are characterized by eruptions of cooler and more viscous lavas than basalt. Therefore, the correct answer is option D.
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