Volcanism

What kind of volcano is associated with mafic mineralogy?

Shield volcanoes.

What type of eruptions are associated with shield volcanoes?

Effusive (non‑explosive) eruptions with flowing, low-viscosity lava.

What is a cinder cone volcano?

A small, steep-sided volcano built from the accumulation of loose volcanic fragments around a vent.

What is a shield volcano?

A broad, domed volcano with gently sloping sides, formed by the eruption of fluid, low-viscosity basaltic lava.

What do shield volcanoes look like?

Wide, gently sloping, shield‑shaped mountains (like a warrior's shield lying on the ground).

What are flood basalts?

Massive, high-volume lava flows that cover large regions or even entire continents, resulting from fissure eruptions.

What is a volcanic plug?

A landform created when magma hardens within a vent on an active volcano and is later exposed after the outer, softer rock erodes away.

What mineralogy is associated with a volcanic plug?

Felsic to intermediate mineralogy (high silica), which makes the magma more viscous.

What eruptions are associated with high-silica volcano types?

Explosive eruptions, as the thick, viscous magma traps gases until pressure builds to a breaking point.

Where do we usually find composite (stratovolcanoes)?

Along subduction zones at convergent plate boundaries (e.g., the "Ring of Fire").

What do composite volcanoes look like?

Tall, steep, symmetrical cones built of alternating layers of lava flows, ash, and volcanic debris.

Where are composite volcanoes found in the Lower 48?

The Cascade Range (e.g., Mount St. Helens, Mount Rainier, Mount Hood).

What eruptions do composite volcanoes experience?

Violent, explosive eruptions characterized by ash clouds, volcanic gases, and deadly pyroclastic flows.

What is a caldera?

A large, cauldron-like depression formed when a volcano erupts and collapses into the partially emptied magma chamber beneath it.

How did Crater Lake form?

It formed following the massive eruption and subsequent collapse of Mount Mazama approximately 7,700 years ago, which was then filled with rain and snowmelt.