Chapter 2 Explain Flashcards
(9 cards)
Explain how geologists gain information about the earth’s interior
Studying how seismic waves (earthquake vibrations) travel through the earth
Describe the theory of plate tectonics
The earth’s crust consists of several plates that float like rafts on the upper mantle
Compare a fault and a fold
Fault-forces on the rock of the crust cause the rock to break
Fold-forces on the rock of the crust cause the rock to bend
How does the elastic rebound theory explain the occurrence of earthquakes?
Earthquakes occur when rocks under strain on either side of a fault rip apart and spring back to an unbent position of little or no strain.
What is the difference between a seismograph and a seismogram?
Seismograph-instrument that detects and records seismic waves
Seismogram-record produced by a seismograph
Explain how scientists classify volcanoes.according to volcanic activity
Active volcano-erupted within recorded history or producing seismic activity
Dormant volcano-inactive but could erupt again
Extinct volcano-will probably not erupt again
Describe the four types of Pyroclasts
Volcanic ash-less than 2mm in diameter, light enough to be carried easily by the wind
Lapilli-larger than volcanic ash but smaller than 64mm
Volcanic blocks-larger than 64mm, lava hardened inside volcano and ejected as a solid
Volcanic bombs-larger than 64mm, ejected lava hardens before it hits the ground, teardrop shape
How do dikes and sills form?
Dike-magma hardens in a vertical fissure
Sill-magma squeezes between two horizontal rock layers and hardens
Contrast the earth’s three major layers
Crust-thin outer layer made of solid rock
Mantle-thick middle layer made of plastic rock, divided into upper mantle, transition zone, and lower mantle
Core-center region of the earth, divided into outer core (liquid) and inner core (solid)
