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Types of Magma I Basaltic, Andesitic & Rhyolitic I FULL VIDEO
Magma exhibits different compositions, each with unique characteristics. The types of magma play an important role in determining the explosiveness of a volcano during an eruption, as well as influencing the formation of volcanic cones in the aftermath. Today, we'll explore the classifications: basaltic, andesitic, and rhyolitic magmas.
__Viscosity is a measure of how thick or sticky a liquid is. It describes the resistance of a fluid (liquid or gas) to flow. In simple terms, a substance with high viscosity is thick and doesn't flow easily, like honey or molasses. On the other hand, a substance with low viscosity is thin and flows more easily, like water. Viscosity is influenced by factors such as temperature and the composition of the fluid.
*Basaltic magma has low viscosity; on the other hand, the viscosity of andesitic magma is intermediate between basaltic and rhyolitic magma. Rhyolitic magma has the highest viscosity. The low viscosity of basaltic magma makes it the least explosive, the intermediate viscosity of andesitic magma results in moderate explosiveness, while the high viscosity of rhyolitic magma makes it the most explosive among the three types.
__Temperature significantly affects magma's viscosity and gas content. The higher the temperature, the lower the viscosity because the heat makes the particles move faster, just like heating chocolate at a higher temperature, making it less viscous or thin. Conversely, at lower temperatures, the viscosity increases. Just like chocolate heating up at a lower temperature, it becomes more viscous or thick.
Basaltic has the highest temperature, ranging from 1000°C to 1200°C; andesitic has a lower temperature than basaltic but higher than rhyolitic, ranging from 900°C to 1000°C, while rhyolitic has the lowest temperature, ranging from 750°C to 900°C. In terms of explosiveness, higher temperature results in the most explosive eruptions, intermediate temperature leads to moderately explosive eruptions, and lower temperature is associated with the least explosive volcanic activity.
__Gas Content: The explosiveness of volcanic eruptions is greatly impacted by the amount of gas in magma. As mentioned earlier, temperature affects gas content, with rising temperatures making magma less sticky and releasing more gases. This reduced stickiness allows bubbles to escape, resulting in less explosive eruptions. On the flip side, lower temperatures make magma stickier, and even though it releases fewer gases, the trapped bubbles make eruptions more explosive. In summary, higher viscosity and the trapping of gas bubbles contribute to more explosive volcanic eruptions.
The gas content of basaltic magma is 1-2%, andesitic magma is 3-4%, and rhyolitic magma is 4-6%. Since basaltic magma has the lowest gas content, it is the least explosive in terms of gas content, while andesitic magma, with an average gas content, is moderately explosive. On the other hand, rhyolitic magma, with the highest gas content, is the most explosive.
__Silica content in magma determines its viscosity and explosiveness. Silica is like sugar added to water. The more sugar, the more viscous it becomes. In magma, the more silica it has, the more viscous it is. Magma with higher silica content tends to have a higher viscosity, making it thicker and leading to more explosive volcanic eruptions due to the increased trapping of gases.
* The silica content in basaltic magma is approximately 50%, in andesitic magma it's around 60%, and in rhyolitic magma, it reaches about 70%. Among these, basaltic magma, with the lowest silica content, is the least explosive; andesitic magma, with an intermediate silica level, is moderately explosive; while rhyolitic magma, having the highest silica content, is the most explosive.
__Explosiveness: In general, even though basaltic magma has a higher temperature, its lower viscosity, gas content, and silica content make it the least explosive compared to andesitic and rhyolitic magma. On the other hand, the explosiveness of andesitic magma is intermediate between basaltic and rhyolitic magma. Finally, rhyolitic magma is the most explosive due to its higher viscosity, gas content, and silica.
__Location of Formation: In this depiction, basaltic magma originates in both continental and oceanic crusts, while andesitic magma is produced in a subduction zone-where one tectonic plate is forced beneath another, often leading to volcanic activity. Rhyolitic magma, on the other hand, is generated within the continental crust.
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23 янв 2024
