PLATE TECTONIC LECTURE NOTES
VOCABULARY: topography, geomorphology, geologic time scale; era; period, epoch, PreCambrian; Paleozoic; Mesozoic; Cenozoic; Quaternary; Pleistocene; Holocene (Recent); fossil; fossil record; revolution; orogeny; relative dating; absolute dating; radioactive isotope; half life; uniformitarianism; catastrophism; lithospheric plates; continental shelf; submarine canyon; continental slope; continental rise; abyssal plain; mid-oceanic ridge; seamount; guyot; coral reef; atoll; ocean trench; plate tectonics; continental drift; sea-floor spreading; Pangaea; Laurasia; Gondwanaland; Sea of Tethys; isostacy; boundaries: convergent, divergent, transform; rift, rift valley; subduction zone; trench; arc system; island arc; volcanoes; continental shield; Ring of Fire; paleomagnetism; polar wandering; normal polarity; reverse polarity; seamounts; hot spot
geomorphology--the study of landforms
topography--the configuration of the land, the landforms
Geologic Time Scale
fossil--any evidence of past life
fossil record--evidence of past life preserved in the rocks which tells about past conditions on earth
revolution; orogeny--mountain building episode
Two means of dating events of the past:
- relative dating--dates one event in relationship to another event
- absolute dating--puts a date on an event in years ± error factor
absolute dating uses methods including radioactive isotopes
radioactive isotope--decays at an absolutely constant rate
half-life--time it takes for half of a radioactive isotope to decay
U238 = 4,510 million years
C14 = 5,730 years
UNIFORMITARIANISM--the processes observed today have occurred in a similar manner during the geologic past
catastrophism--processes happen as giant catastrophes such as Noah's Flood depositing hugh masses of sediments on the bottom of the sea floor which became rocks
PLATE TECTONICS
outer 125 miles--both crust and top of mantle is composed of two types of material:
top--lithosphere--made of sima and sial, rigid
below--asthenosphere--low strength, low seismic velocity--40-150 miles deep
lithospheric plate--portion of crust which moves over the asthenosphere
sea floor topography
- continent
- continental shelf--smooth gently sloping area peripheral (fringing) the continent, 300-600' average 400', few feet per mile; submarine canyons
- continental slope--more steeply inclined ocean floor, edge of continents, to 12,000', several 100' per mile
- continental rise--gently sloping surface at the base of the continental slope, often considered part of it
- abyssal plain--extensive, level area of deep ocean floor; 10,000-20,000'; 40% of ocean floor
- mid-oceanic ridge--mountain range
- oceanic trench--usually border continent, some over 1000 miles long and 100 wide
- islands and submarine volcanoes; seamounts, guyots, coral reefs, atoll
plate tectonics; continental drift; sea-floor spreading
Alfred Wegener 1912--200 million years ago
Pangaea split
maps of boundaries
earthquakes
volcanoes
types of boundaries and examples:
divergent--move apart
transform--slide past
convergent--come together
Transect of Plates
age and depth of ocean sediments--newer ocean floor at the midoceanic ridges so the age of the sediment on the bottom of the floor there is younger and it is covered by a thinner deposit
continental shields--ancient, stable crystalline rock areas
isostacy--balancing of the earth's crust
references: Smithsonian Magazine January 1975 and February; and Wilson, Continents Adrift and Continents Aground reprints from Scientific American
four factors are involved in the differentiation of landforms
- geologic structure
- tectonic activity (folding, faulting, volcanism)
- gradation (erosion--transportation and deposition)
- time (stage)
Go to the Plate Tectonic Review Questions
Dr. M. H. Hill's Homepage