After reviewing the graph you posted above, there is one radioactive isotope that has a half life that is approximate to the same as the estimated time of the origin of Earth.
The radioactive isotope is called Uranium 238. You can also write this out as U-238 or uranium/u. Any of these are acceptable for the answer.
This statement is true. Soil color only reflects the amount of organic matter that is currently present in the soil. If the soil seemed to be much darker, it means that the soil has a greater amount of organic materials which makes it better.
The answer to your question is hindiusim
You would go upstream as in north if you would go down stream it would be south
