Why do shield volcanoes have very gently sloping sides?
A) Their andesite composition produces huge ash flows that spread over a large area.
B) Their andesite and rhyolite have low viscosity because of their water content, and spread over a low slope.
C) Their basalt flows have low viscosity, so the lava solidifies as gentle slopes.
D) Their basalt ash spreads out widely in the strong winds over the open ocean.
E) Their basalt magmas blow out violently from all of their pent up steam.

Question

Quizplus · Accepted Answer

Shield volcanoes are composed of basaltic lava flows that have low viscosity, meaning they are relatively thin and easily flow over the ground. Their gentle slopes are a result of the lava solidifying as it flows, gradually building up the volcano's shape over time.

Why Do Shield Volcanoes Have Very Gently Sloping Sides