Radiometric dating solar system
It looks like this: Most of the other measurements for the age of the Earth rest upon calculating an age for the solar system by dating objects which are expected to have formed with the planets but are not geologically active (and therefore cannot erase evidence of their formation), such as meteorites.
Below is a table of radiometric ages derived from groups of meteorites: As shown in the table, there is excellent agreement on about 4.5 billion years, between several meteorites and by several different dating methods.
The actual underlying assumption is that, if those requirements have not been met, there is no reason for the data points to fall on a line.
The resulting plot has data points for each of five meteorites that contain varying levels of uranium, a single data point for all meteorites that do not, and one (solid circle) data point for modern terrestrial sediments.
For example: Also note that the meteorite ages (both when dated mainly by Rb-Sr dating in groups, and by multiple means individually) are in exact agreement with the solar system "model lead age" produced earlier.
Young-Earthers have several methods which they claim to give "upper limits" to the age of the Earth, much lower than the age calculated above (usually in the thousands of years).
Some of these rocks are sedimentary, and include minerals which are themselves as old as 4.1 to 4.2 billion years.
This lower limit is at least concordant with the independently derived figure of 4.55 billion years for the Earth's actual age.
And from the slope of the line we can compute the amount of time which has passed since the pool of matter became separated into individual objects.
See the Isochron Dating FAQ or Faure (1986, chapter 18) for technical detail.
Further, the processes of erosion and crustal recycling have apparently destroyed all of the earliest surface.
The oldest rocks which have been found so far (on the Earth) date to about 3.8 to 3.9 billion years ago (by several radiometric dating methods).