Final answer:
Silica-rich lava creates steep volcanoes because it is viscous and solidifies quickly, leading to the buildup of material in a steep-sided structure.
Step-by-step explanation:
Steep volcanoes are often associated with silica-rich lava, which is more viscous comparing to lava with lower silica content. Silica-rich lava tends to flow more slowly and solidify quicker upon eruption, leading to the buildup of materials around the vent.
The process of building the volcano 'from small to big' through repeated eruptions of this viscous lava results in the formation of a steep-sided structure. This phenomenon contrasts with volcanoes built from less viscous lava, which tends to spread out more widely, resulting in broader slopes and flatter shield volcanoes like those found in the Hawaiian Islands.