![]() ![]() Thingvellir Valley and Lake Thingvallavatn, Thingvellir National Park, Thingvellir, Iceland.įirst slide details. This is a quiet eruption with lava spewing out violently. This is an explosive eruption caused by high-viscosity magma. Which statement best describes this eruption This is a quiet eruption caused by low-viscosity magma. The Hawaiian volcanoes are the most famous examples. They are the largest of all the volcanoes on the earth. Basaltic lavas are relatively thin and are very fluid when erupted. They also tend to be shield volcanoes with gently sloping slides. Biology High School answered expert verified A volcano erupts, and lava flows down a mountainside. Basaltic magma doesn’t have high viscosity. Rift volcanoes generally issue nonviolent streams of lava, instead of explosively erupting. For example, Iceland was formed where the mid-ocean ridge met with a mantle plume – a ‘hotspot’ of abnormally hot rock in the mantle – and eruptions of lava built volcanoes and filled rift valleys. Higher dissolved silicate concentrations increase fluid density and viscosity leading to slower less-buoyant flow with increasing PT. This process can also form volcanic islands. The tectonic plates are spreading apart allowing soft molten rock to bubble up between the plates. Basalt has highest temperature which causes atoms to spread farther apart, thus decreasing. It stretches all around the globe and is more than 64,000 kilometers (40,000 miles) long. The viscosity of magma increases with the content of silica. The mid‐ocean ridge is a continuous, underwater seam of mountains and volcanoes that form where divergent tectonic plates meet. Hills covered by volcanic ashes, Great Rift Valley, Tanzania, East Africa. Spreading may have created East Africa's volcanic Great Rift Valley. When spreading centers develop within continents, they form new plate boundaries and trigger volcanic activity. Spreading centers can be found under the sea or on land. Three factors that affect magma viscosity are temperature composition and presence of dissolved gases. In these zones, plates move away from each other, decreasing the pressure on the underlying mantle, allowing it to rise and melt, forming magma. ![]() Silicon and oxygen combine to form silica tetrahedra. What happens as the temperature of magma drops As magma loses heat to the surrounding rocks and its temperature drops things start to change. Volcanoes called rift volcanoes are formed in spreading centers. The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity. Magma high in silica has higher viscosity. Sorry, your browser doesn't support embedded videos. ![]()
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