STUDY GUIDE – UNIT 9 – PLATE TECTONICS
CONTINENTAL DRIFT
MID-OCEAN RIDGES
Continental “fit” : coastlines match up
Rocks, minerals and fossils: similar age and
composition
zone of divergence: plate boundary under ocean,
basalt, addition of new rock pushes plates apart
Mid-Atlantic Ridge, Iceland
age of basalt:  farther away from ridge
magnetic reversal: magnetic minerals
create same pattern on both sides,
Earth’s polarity has reversed
EARTH’S LAYERS / CRUST
crust, mantle, lithosphere, asthenosphere,
oceanic: basaltic, more dense,
thin layer, mainly under oceans
continental: granitic core with thin layer of
sedimentary rock, less dense,
thick layer, mainly as a continent
mantle: convection currents
outer / inner core: inferred properties, metals,
which layers are S or L
Know how to read ESRT chart
on Earth’s inferred properties
EVIDENCE OF CRUSTAL MOVEMENT
deformed rock strata: tilting, folding, faulting
anticline /syncline, faults: lateral, normal, reverse
displaced rock strata, displaced fossils
uplift = benchmarks, raised beaches
CRUSTAL ACTIVITY
plate tectonics: plates in motion on
convection cells in mantle
crustal activity: quakes, volcanoes, trenches, midocean ridges, mountains
colliding: convergence, subduction or folding,
volcanoes, earthquakes, mountains
Mt. St. Helens, Himalayans
moving apart: divergence, mid-ocean ridges,
volcanoes, earthquakes
Mid-Atlantic Ridge
sliding: faulting, earthquakes
San Andreas Fault
Circum-Pacific Belt = Pacific Plate boundaries
VOLCANOES/MOUNTAINS
colliding plates, convergence
C to C = mountain uplift (orogeny)
Himalayans, Andes
O to C = volcano formation/mountain uplift,
subduction, oceanic more dense (under)
Mt. St. Helens, Cascade Range
Hot spots, what causes them, Hawaii
EARTHQUAKES
plates sliding, faults, San Andreas Fault
focus, epicenter, seismic waves
P and S waves: characteristics of each
P and S travel faster in denser materials
S only thru solids = part of core is liquid
“shadow zone” : region w/no waves
P and S waves have bent paths
properties of Earth’s interior : inferred from P
and S waves, outer core is liquid
P and S arrival time:  diff arrival time = farther
away epicenter
distance to epicenter -- need diff. between
P and S arrival times and ESRT
arrival time of P and S waves -- need
epicenter distance and ESRT
time of earthquake -- need P wave arrival
time and time of P wave travel
locating exact epicenter -- need 3 locations
to pinpoint, point of intersection