How have a rock that was formed at the same time as the Earth was formed. How old is the rock? How much of the original uranium-238is likely to be left today in that rock? Solution It has been theorized that the actual age of the earth is about 4.6 billion years old.According to some geologists,one of the remarkable features of the old rocks is that they are not formed from the primordial crust of the Earth.Rather, they are formed from lava and sediments that deposited in shallow water which indicates that Earth was already formed before rocks began to deposit.Still there are some geologists who suggest that the oldest rocks were formed as remnants of the primordial crust of Earth.These rocks are known as faux-amphibolites.The oldest rock were formed 3.9 billion years old.The half life of uranium-238 is 4.5 billion years and half of the uranium-238 present now has been decayed to lead 206.So half of the , original uranium- 238 is likely to be left today in that rock..

1. How have a rock that was formed at the same time as the Earth was formed. How old is the
rock? How much of the original uranium-238is likely to be left today in that rock?
Solution
It has been theorized that the actual age of the earth is about 4.6 billion years old.According to
some geologists,one of the remarkable features of the old rocks is that they are not formed from
the primordial crust of the Earth.Rather, they are formed from lava and sediments that deposited
in shallow water which indicates that Earth was already formed before rocks began to
deposit.Still there are some geologists who suggest that the oldest rocks were formed as
remnants of the primordial crust of Earth.These rocks are known as faux-amphibolites.The oldest
rock were formed 3.9 billion years old.The half life of uranium-238 is 4.5 billion years and half
of the uranium-238 present now has been decayed to lead 206.So half of the , original uranium-
238 is likely to be left today in that rock.