Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What is the primary characteristic of composite volcanoes?

1. They are exclusively made up of lava flows.

2. They are built by layers of ash and cinder.

3. They are defined by their quiet eruptions.

4. They are formed by both lava flows and layers of ash and cinder.

The correct answer is: They are formed by both lava flows and layers of ash and cinder.

Composite volcanoes, also known as stratovolcanoes, are characterized by their formation through the interplay of both lava flows and layers of ash and cinder. This combination results in a steep, conical shape, which is a defining feature of these volcanoes. The lava flows contribute to the construction of the volcano's solid core, while the alternating layers of ash and cinder enhance its height and stability. The eruptions of composite volcanoes can vary in intensity, often displaying a range of explosive and effusive activities. This variability is influenced by the composition of the magma and the presence of volatiles. Thus, the dual nature of their formation—consisting of both lava and pyroclastic materials—predominantly defines composite volcanoes, making this choice the most accurate representation of their primary characteristic.