10.1 Volcano

How do volcanoes relate to mid ocean ridges?

A mid-ocean ridge system consists of a series of volcanoes that form along a spreading center. As the tectonic plates move apart, mantle pressure decreases and magma wells up from Earth's interior.

Explain how volcanoes form at divergent boundaries?

A spreading center on the ocean floor marks the divergent boundary where oceanic crust moves apart.

What is a volcano?

A volcano is a geological feature that forms around a fissure in Earth's crust.

Common gasses that are found in magma?

Common gases in the magma include water vapor and carbon dioxide, as well as lesser amounts of sulfur, chlorine, and fluorine.

What is the foundation of the volcanic structure?

Conduits often branch, carrying these materials to smaller vents off the main volcanic structure.

Decompression melting

Decompression melting occurs when solid, hot material rises to Earth's surface.

Other than tectonic plate boundaries, where else can volcanoes form?

Hot Spots

Where does most volcanism occur?

However, most volcanism occurs in the ocean along divergent plate boundaries.

Intermediate lava

Intermediate (e.g., andesitic) lava contains 53 to 65 percent silica. This lava forms from magma that melts through oceanic crust that is rich in silica. However, it does not contain as much silica as the aluminosilicate rocks found in continental crust. This type of lava often forms at convergent plate boundaries.

What is lava?

Lava is magma expelled at Earth's surface.

How does magma form?

The magma forms when rock material melts, or becomes molten, close to an Earth mantle-crust interface.

Ultramafic lava

Ultramafic lava contains less than 45 percent silica. This lava is extremely rare on the planet today. It formed early in Earth's history when the planet's surface was hotter and the crustal material was still primarily mafic.

How do volcanoes form at convergent boundaries?

Volcanoes also form along convergent boundaries where tectonic plates come together. As the plates converge, they produce a unique feature called a subduction zone outlined by a trench, a deep depression in the ocean floor. As the denser plate is subducted along the trench, it is recycled back into the mantle.

Hot Spot

A hot spot is a relatively stationary plume of magma that scientists think originates at the mantle-core boundary.

What is a conduit?

A conduit is the means by which magma gets from Earth's interior to an opening or vent at Earth's surface, through which it erupts as lava.