Seismic Waves, Structure of the Earth, Earthquakes, and Plate Tectonics
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Created by:
nysportsrule on April 18, 2011
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25 terms
Terms | Definitions |
|---|---|
 P-waves | fastest seismic wave; longitudinal waves that pass through liquids and solids |
| S-waves | second fastest seismic waves; transverse waves that pass only through solids |
| Surface waves | third slowest seismic waves; travel along the surface of Earth and not through the interior |
| Crust | upper layer of Earth; must be solid because both S-waves and P-waves travel through it |
| Upper Mantle | Asthenosphere; plastic-like, but solid, layer; We know it is less dense than the lower mantle due to the refraction of S-waves and P-waves at that barrier |
| Lower Mantle | Must be solid because both S-waves and P-waves pass through it |
| Outer Core | Must be liquid because only P-waves pass travel through it |
| Inner Core | We believe it is solid because P-waves refract at the barrier and move faster through it than the less dense outer core |
| Epicenter | Location on the crust where seismic waves originated |
| Seismograph | Instrument used to measure the intensity of seismic waves |
| Order of waves measured on a seismograph | P-waves hit first, then S-waves, then surface waves |
| Richter magnitude | Determined by the maximum S-wave intensity |
| Normal fault | the head wall falls down relative to the foot wall |
| Reverse fault | The head wall moves up relative to the foot wall |
| Strike-slip fault | The two walls move side to side relative to each other |
| First theory of the continents | Shrinking Earth Theory |
| Shrinking Earth Theory | Continents do not move; Core is cooling down, causing the Earth to slowly shrink; Contraction of the Earth is what causes mountains to form, earthquakes to happen, etc. |
| Plate Tectonics | Crust is divided into plates that move |
| Sea Floor Spreading | Occurs at ocean ridges; Plates move because magma comes up through the ridge, forming new rock and pushing the old rock outwards |
| Plate Boundaries | Convergent boundaries, where to plates more towards eachother |
| Oceanic-Oceanic convergence | one of the plates will slide underneath the other, which is called subduction. This creates a trench in the ocean. |
| Oceanic-Continental convergence | Oceanic plate subducts under the continental plate |
| Continental-Continental convergence | Tends to result in a mountain building episode, and results in a normal fault |
| Divergent boundaries | Two plates move away from one another. Oceanic ridges are examples of this; This will give us a reverse fault |
| Transform Boundaries | Two plates slide next to each other. This is also a strike-slip fault |
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