Lava line dating
The slope of the line determines the date, and the closeness of fit is a measure of the statistical reliability of the resulting date.
Technical details on how these dates are calculated are given in Radiometric dating. As with any experimental procedure in any field of science, these measurements are subject to certain "glitches" and "anomalies," as noted in the literature.
The Deccan Traps in India – between 17°–24° North and 73°–74° East – are a place where you can find layer upon layer of solidified rock.
This region is thought to have been the site of extremely powerful volcanic activity in the past, so powerful that it caused mile-deep lava over an area as large as the state of California.
The impact near Chicxulub, Mexico – 66 million years ago – is believed by many researchers to have killed the dinosaurs and ushered in the age of mammals.
Here is one example of an isochron, based on measurements of basaltic meteorites (in this case the resulting date is 4.4 billion years) [Basaltic1981, pg. Skeptics of old-earth geology make great hay of these examples.
For example, creationist writer Henry Morris [Morris2000, pg.
The Berkeley researchers say the impact probably “rang the Earth like a bell,” triggering powerful earthquakes and volcanos around the globe, including those that created the Deccan Traps.
The Berkeley researchers – who published their work online April 30 in the The Geological Society of America Bulletin – cited the “uncomfortably close” coincidence between the Deccan Traps eruptions and the asteroid impact 66 million years ago.