Answer;
-Birds separated from dinosaur relatives 120 million years ago.
-The oldest Earth rocks are 3.9 billion years old.
Step-by-step explanation;
-Geologists often need to know the age of material that they find. They use absolute dating methods, sometimes called numerical dating, to give rocks an actual date, or date range, in number of years. This is different to relative dating, which only puts geological events in time order.
-Absolute dating provides a numerical age or range in contrast with relative dating which places events in order without any measure of the age between events. Most absolute dates for rocks are obtained with radiometric methods. These use radioactive minerals in rocks as geological clocks.