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4 Principles of Stratigraphy

horizontality, stratigraphic superposition, lateral continuity, cross-cutting relationships

gaps in rock record because

unconformities

unconformities

gap in stratigraphic sequence that marks absence in part of rock record

types of uncomformities

angular, noncomformity, disconformity

correlation

equating ages of strata that come from two or more different places

Wegners Theory of continental drift

matching continents, climate, fossils and rock formations

Problem with wegners theory

couldn't explain why or how continents moved

2 piece of info recorded by magnetite

which way is north and orientation

divergent margin

boundary along which two plates move apart

convergent

two plates come together
collision
subduction zone

subduction zone

lithosphere plate plunges into mantle beneath another plate

hot spot

rising mantle plume of material partially melts lithosphere above it (hawaii)

what drives plate motion?

still active research, but thermal motion of mantle is partially responsible

viscosity

ability of a liquid to flow

seismology

study of earthquakes and seismic waves

seismic waves

elastic shock wave that travels outward in all directions

stress

pressure with direction

focus

point under the surface where EQ begins

epicenter

point on Earth's surface directly above focus

body wave

travels through earth's interior

surface wave

travels across earth's surface

P-wave or compressional wave

pass through any medium
alternating pulses of compression and expansion
=============>

S or shear wave

side to side or up/down forces
not transmitted through liquids
travel slower than P-waves
~~~~~~~~~~>

how to locate earthquakes

triangulation
3 stations determine distances to epicenter
EQ is where three circles intersect
the greater the interval b/w P and S wave, the farther away the EQ is

Richter Magnitude scale

intensity based on amplitudes of seismic waves on seismograph
logarithmic scale (1-10)

Mercalli Scale

what people feel/see
damage

love waves

fast shaking, side to side
arrive first

Rayleigh Waves

undulating up and down
arrive second

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