Radiometric dating--the process of determining the age of rocks from the decay of their radioactive elements--has been in widespread use for over half a century.
I take "extinct" to mean "decayed to the point that it cannot be detected".
(excellent pun and emphasis both mine) Among all the elements that occur on Earth are 150 stable isotopes and 158 unstable ones, making 308 in all.
Of the 158 unstable ones, 121 are either extinct or exist only because they are constantly renewed, like carbon-14.
Many Christians have been led to distrust radiometric dating and are completely unaware of the great number of laboratory measurements that have shown these methods to be consistent.
Many are also unaware that Bible-believing Christians are among those actively involved in radiometric dating.
If I am using that word correctly, then in what sense does an extinct element "occur on Earth"? The matter that makes the earth came from some supernova(s) in the distant past.