At 0 years, an event took place which is known as metamorphosis of igneous rock i.e., formation of igneous rocks from melted magma.
Strontium-90 is a radioactive element which undergoes beta decay to form yttrium-90. It has a half life of approximately 28 years and decay energy of 0.546 MeV. This radioactivity is used by geologist to estimate the age of the rock, fossils, meteorites etc. Other radioactive elements used by the geologists are carbon-40, potassium-40 etc.
Radiometric clock is set when the rock was formed in the past i.e., the moment when an ingenious rock was solidified from molten magma.
they compare fossils to other fossils to see if skeleton changes are observed in a species over time it indicates that there is genetic change going on within the species
