Forces Within Earth (Earthquakes)
primary wave
(P-wave) squeeze and push rocks in the direction along which the waves are traveling
secondary wave
(S-wave) slower than P-waves, so they are the second set of waves to be felt
fault
Any fracture or system of fractures along which Earth moves
elastic deformation
Caused when a material is compressed, bent, or stretched
Cinder Cones
When eruptions eject small pieces of lava into the air, cinder cones form as this material, often called cinders, scoria, or tephra, falls back to Earth and piles up around the air
plastic deformation
When stress builds up past a certain point, called the elastic limit
Crater
a bowl-shaped depression
Shield Volcano
a mountain with broad, gently sloping sides and a nearly circular base
Foreshock
a small earthquake that comes before a major earthquake
Conduit
a tubelike structure that lava travels through to get to the surface
Aftershock
adjustments in the crust after an earthquake
Volcanism
describes all the processes associated with the discharge of magma, hot fluids, ash, and gases
Composite Volcanoes
formed of layers of ash and hardened chunks of lava from violent eruptions alternating with layers of lava that oozed downslope before solidifying. They are generally cone-shaped with concave slopes, and are much larger than cinder cones.
Flood Basalts
forms when lava flows out of long cracks in Earth's crust
Calderas
larger depressions
epicenter
surface waves originate here and spread out
strain
the deformation of materials in response to stress
Fissures
the long in Earth's crust that lava flows out of
Vent
the opening that lava emerges through
focus
the point of failure where the waves originate
stress
the total force acting on crustal rocks per unit of area
seismic wave
the vibrations of the ground produced during an earthquake
Hot Spots
unusually hot regions of Earth's mantle where high-temperature plumes of magma rise to the surface
fracture
when a mineral breaks into pieces with arclike, rough, or jagged edges