Answer:

The chemical composition of magma AFFECTS its physical properties, which in TURN have a major influence on the landform built by a volcanic eruption. ... As the silica content increases, these rock types generally become more viscous; as the magmatic gas content increases, they become more explosive.

Explanation:The volume of material released in any one eruption can vary enormously from a few cubic metres of magma to as much as 3,000 cubic km (720 cubic miles). A series of small eruptions usually builds up mounds close to the vent, whereas large-volume eruptions tend to disperse their products over a greater distance. Effusive eruptions FORM lava plateaus or gently sloping shield volcanoes; moderately explosive eruptions form stratovolcanoes; and giant explosive eruptions form plateaus of lava or ash flows and almost always form a caldera several kilometres in diameter over the eruption site. Naturally, since many other factors are INVOLVED in determining volcanic landforms, there are exceptions to these rules