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:

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


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

plate tectonics; continental drift; sea-floor spreading
Alfred Wegener 1912--200 million years ago
Pangaea split
maps of boundaries


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
Go to the Plate Tectonic Review Questions

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