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