Answer:
Shield Volcano:
Magma Composition: Shield volcanoes are typically associated with basaltic magma, which is low in silica content and more fluid. Basaltic magma has low viscosity, allowing it to flow easily and spread out over large areas before solidifying. This low viscosity magma results in relatively gentle eruptions with lava flows that can extend for long distances.
Eruption Style: Shield volcanoes are characterized by relatively calm and non-explosive eruptions. The basaltic magma erupts from a central vent or a series of fissures on the volcano's flanks, leading to the formation of extensive lava flows. These eruptions are often effusive, with the lava flowing steadily rather than explosively.
Volcanic Cone Shape: Shield volcanoes have a broad and gently sloping profile, resembling a shield or a flattened dome. The lava flows from multiple eruptions accumulate and spread out, gradually building up the volcano over time. The accumulation of multiple thin, basaltic lava flows creates the characteristic shield-like shape.
Composite Cone (Stratovolcano):
Magma Composition: Composite cones are associated with andesitic to rhyolitic magma, which is higher in silica content and more viscous compared to basaltic magma. This higher viscosity magma is stickier and less fluid, making it more prone to trapping gas and generating explosive eruptions.
Eruption Style: Composite cones are known for their explosive eruptions. The higher viscosity magma traps gas bubbles, leading to pressure buildup and violent eruptions. These eruptions can produce pyroclastic flows, ash clouds, and volcanic debris such as ash, cinders, and volcanic bombs. Composite cones can have both explosive eruptions and periods of effusive eruptions.
Volcanic Cone Shape: Composite cones have a steep and conical shape, with steep sides and a narrow summit crater. The eruption of viscous magma, combined with explosive activity and the accumulation of volcanic debris, leads to the steep slopes and distinct cone-like appearance of these volcanoes.
Step-by-step explanation: