Final answer:
The overall average composition of a stratovolcano is typically andesite, which is an intermediate volcanic rock. Andesite is rich in silica and contains minerals such as plagioclase feldspar and amphibole. This composition influences the stratovolcano's eruptive behavior, with andesitic magma tending to result in explosive eruptions due to its high viscosity and gas content.
Step-by-step explanation:
The overall average composition of a stratovolcano can vary depending on the specific volcano, but generally they are composed of alternating layers of lava, ash, and other volcanic materials. The most common rock type found in stratovolcanoes is andesite, which is an intermediate volcanic rock. Andesite is rich in silica and contains minerals such as plagioclase feldspar and amphibole.
The composition of a stratovolcano can influence its eruptive behavior. Andesitic magma, which is viscous and has a high silica content, tends to trap gas bubbles within the magma chamber. This can result in explosive eruptions, as the pressure builds up and eventually causes the magma to violently explode. The ash and pyroclastic material produced during these eruptions can be ejected high into the atmosphere and travel long distances.