From: DV (Avatar) 30/11/2001 21:51:09 Subject: re: ROCK LEGEND NOTES post id: 518838 Is the middle of the earth older or younger? My answer will probably not be satisfying. C'est la vie. What might we mean by the age of a particular part of the earth? We might mean the average amount of time since the atoms that make up that part have arrived, in which case there will not be a great deal of difference. (I say this without regard to the theoretical creation of the earth-moon system by a collision of two major planets, but not because I regard that hypothesis as unlikely.) We might mean the average time since the actual rocks making up that part of the earth formed. In this case, the crust will have a lower average "age" than the mostly metallic crystalline material at the centre of the solid core. (The edge of the solid core has a more exciting time, however.) By the way, seismic investigations indicate that the solid core rotates at a slightly different rate from that of the crust and mantle!