Patterns and Locations of Volcanoes and Earthquakes

Fault

that is a crack in the Earth's surface where movement takes place

epicenter

the point on Earth's surface directly above the focus; energy that reaches the surface is greatest at this point.

Seismograph

used to measure the waves of an earthquake

Types of Volcanoes

1. spreading center volcanism (DIVERGENT) 2. subduction zone volcanism (CONVERGENT)

volcano

A mountain that forms when molten rock (called magma) is forced to the Earth's Surface

chains of volcanoes

As the tectonic plates continue to move over a stationary hotspot, the volcanoes break away and move along with the plate allowing new volcanoes to form in their place.

San Andreas Fault

Located in California is an example of an active transform plate boundary.

How Magma forms at a Divergent Boundary

Mantle material rises to fill the space opened by separating tectonic plates. As the pressure decreases, the mantle begins to melt and rise up Because magma is less dense than the surrounding rock, it rises toward the surface where it forms new crust on the ocean floor

Theory of Plate Tectonics

The evidence proves that there is a distinct relationship between seismic activity, volcanic activity, and the lithospheric plate boundaries.

Seismic Data

The interaction along plate boundaries results in an increased frequency of earthquakes at those locations. Additionally, stronger earthquakes are more likely to occur along active plate boundaries.

Earthquake

Vibrations that cause the breaking of rocks. These vibrations move in all directions through the earth. They begin at a point along a fault

subduction zone volcanism

Volcanic activity at convergent plate boundaries occurs as the two plates converge or collide on one another. The most volcanically active belt on Earth is known as the Ring of Fire, a region of volcanic activity that happens at subduction zones surrounding the Pacific Ocean. What Forms: Volcanoes, Volcanic Island Arcs, Mountains, and Subduction Zones

spreading center volcanism

Volcanic activity at divergent plate boundaries occurs as the plates pull apart which allows magma to fill the rift zone between the separating plates. What Forms: NEW CRUST at Mid-Ocean Ridges and Rift Valleys

Pacific Ring of Fire

a region of high volcanic and seismic activity that surrounds the majority of the Pacific Ocean Basin

Hotspot

an area in the mantle from which heat rises in the form of a thermal plume from deep within the Earth. They are stationary while the plates move

Convection Currents

currents in the mantle that result in the movement of lithospheric plates

seismic waves

energy that spreads outward in all directions as vibrations

focus

is the point in the crust, or mantle, where energy is released (seismic waves) or where the earthquake begins

Magma

molten material beneath or within the earth's crust (inside the volcano). It rises through the crust to form volcanoes and volcanic island arcs.

Lava

molten material outside the volcano (at or above Earth's surface). Magma that reaches Earth's surface

Strong earthquakes

more common at transform and convergent plate boundaries.

Volcanoes at convergent boundaries

occur where subducting oceanic crust is melted

Volcanoes at divergent boundaries

occur where upwelling magma pushes between plates (rift zones) as the plates move apart