Isotopic age dating patterson
The slope of the isochrone is used to calculate the age of the rock (here, 4.55 billion years is the best fit line in the middle).
This method allows us to calculate the ages of rocks formed at the same time.
So why is the age of the Earth so tricky to calculate?
One major problem is that the earth has plate tectonics—the rocks are constantly recycled through the Earth, giving them all different ages.
Measured 4He concentrations indicate accumulation of radiogenic 4He that is qualitatively consistent with the age progression indicated by the 36Cl/Cl ratios, but the flux of external 4He from the underlying crust has not been quantified and is not constant throughout the aquifer.
A two-dimensional numerical hydrodynamic transect of the aquifer was modeled from the area of the Uweinat Uplift to the northern Bahariya Oasis. AU - Sultan, Mohamed AU - Lu, Zheng Tian AU - Lehmann, Bernhard AU - Purtschert, Roland AU - Alfy, Zeinhom El AU - Kaliouby, Baher El AU - Dawood, Yehia AU - Abdallah, Ali PY - 2005/1Y1 - 2005/1N2 -  Measurements of radiochlorine (36Cl), radiogenic noble gases (4He and 40Ar), and stable chlorine isotope ratios were obtained to assess the residence time of groundwater in the Nubian Aquifer of the Western Desert of Egypt.
Predicted groundwater velocities in the deep portion of the aquifer are 0.5-3.5 m/yr with groundwater residence times up to 9 × 10He), a consistent picture of the Nubian Aquifer has emerged in which lateral flow from a southern recharge area dominates the deep horizons, while shallow horizons contain younger, autochthonous recharge. Measured 36Cl/Cl ratios yield apparent residence times from ∼0.2 to 1.2 × 106 years in the deep (600-1200 m) groundwater (assuming constant Cl) and ≤0.16 × 10 6 years in the shallow (37Cl in the groundwater strengthen the application of the 36Cl dating method by constraining Cl sources and identifying groundwater mixing.
A two-dimensional numerical hydrodynamic transect of the aquifer was modeled from the area of the Uweinat Uplift to the northern Bahariya Oasis.
Predicted groundwater velocities in the deep portion of the aquifer are 0.5-3.5 m/yr with groundwater residence times up to 9 × 105 years; residence times up to 1.3 × 106 years are predicted in the confining shale.
Search for isotopic age dating patterson:
The Moon has unaltered rocks—but Patterson made this measurement a decade before Moon samples were brought to Earth!