Question

Which best describes the way composite volcanoes are built up?

1) The accumulation of blocks and bombs that have been ejected over time
2) Repeated lava flows
3) Alternating layers of cinders and ash embedded with lava flows

Answer 1

Composite volcanoes are built up through alternating layers of cinders, ash, and lava flows, typically at subduction zones or continental collision zones where tectonic activity creates the necessary magma.

Step-by-step explanation:

The best description of how composite volcanoes are built up is through alternating layers of cinders and ash embedded with lava flows. Unlike shield volcanoes, which are primarily built up by repeated lava flows, or cinder cone volcanoes that are formed from the accumulation of volcanic blocks and bombs, composite volcanoes, also known as stratovolcanoes, are built by a combination of explosive volcanic activity and lava flows. This results in a classic conical shape with layers of hardened lava flows, tephra, pumice, and volcanic ash.

These composite structures are often located at subduction zones, where one tectonic plate moves under another, or at continental collision zones, where tectonic plates are pushing against each other. The intense pressure and heat from these tectonic processes cause rock to melt in the Earth's mantle, creating the magma that feeds the volcanic eruptions.