Which volcanic structure is characterized by alternation of lava layers and volcanic ash and other materials?

Which volcanic structure is characterized by alternation of lava layers and volcanic ash and other materials?

• A. Cinder cone volcano
• B. Shield volcano
• C. Composite volcanoes
• D. Fault

Answer: (C)

Composite volcanoes, also called stratovolcanoes, are built up from alternating layers of hardened lava flows and volcanic ash and other ejecta. When magma erupts explosively, it blasts out ash, pumice, and other tephra that settle around the vent, creating a layer. Between explosive episodes, lava flows spread and solidify, adding another layer on top. Repeating these cycles over time creates a tall, steep-sided cone with a distinct, layered structure. This contrasts with cinder cones, which form mainly from blasted tephra piling around the vent with little lava flow to create layers; shield volcanoes form from many long-lasting lava flows of low-viscosity magma that spread out to make broad, gentle slopes; and a fault is not a volcanic structure at all.

Composite volcanoes, also called stratovolcanoes, are built up from alternating layers of hardened lava flows and volcanic ash and other ejecta. When magma erupts explosively, it blasts out ash, pumice, and other tephra that settle around the vent, creating a layer. Between explosive episodes, lava flows spread and solidify, adding another layer on top. Repeating these cycles over time creates a tall, steep-sided cone with a distinct, layered structure. This contrasts with cinder cones, which form mainly from blasted tephra piling around the vent with little lava flow to create layers; shield volcanoes form from many long-lasting lava flows of low-viscosity magma that spread out to make broad, gentle slopes; and a fault is not a volcanic structure at all.