Answer:
Large volumes of A'A' lava causes the steep slopes of stratovolcanoes (composite cones).
Explanation:
The A'A' lava has a rapid flow rate and bears a very high viscosity. This viscosity which is already low enhances as the lava flows rapidly and loses heat at a high pace. This combined action of A'A' lava ceases it from spreading on large areas and results in the formation of steep slopes. The Pahoehoe lava can also act like A'A' lava if the slopes are already steep.
