No one is really certain how the earth was formed, but it is clear that at one time the earth was liquid. Today we know that there is still a liquid core which is surrounded by a mantle and finally a crust up to twenty miles thick. It is on this crust that we all live.
Introduced by Dr. Tom Gaskell.
(Recording, first shown on Oct, 28)
Repeated on Tuesday at 11.20 a.m.