Radiometric dating and the geological time scale courtship dating video
Laws of Stratigraphy Original Horizontality - sedimentary strata are deposited in layers that are horizontal or nearly horizontal, parallel to or nearly parallel to the Earth's surface.
Thus rocks that we now see inclined or folded have been disturbed since their original deposition.
With this discovery, Radiometric dating techniques became possible, and gave us a means of measuring absolute geologic time.
Radiometric Dating Radiometric dating relies on the fact that there are different types of isotopes.
We call such a break in the stratigraphic record a hiatus (a hiatus was identified in our trash pit example by the non-occurrence of the Ceramic Cups layer at the UNO site).
When we find evidence of a hiatus in the stratigraphic record we call it an unconformity.
Over the past 150 years detailed studies of rocks throughout the world based on stratigraphic, paleontologic, and correlation studies have allowed geologists to correlate rock units throughout the world and break them into time stratigraphic units.
Assumes that we know the rate at which the salts (Na, Cl, Ca, and CO3 ions) are input into the oceans by rivers, and assumes that we know the rate at which these salts are removed by chemical precipitation.
Calculations in 1889 gave estimate for the age of the Earth of 90 million years.
Stratigraphic Superposition - Because of Earth's gravity, deposition of sediment will occur depositing older layers first followed by successively younger layers.
Thus, in a sequence of layers that have not been overturned by a later deformational event, the oldest layers will be on the bottom.