The devastation of the Flood (which i believe was world wide) made changes in the earth that would take millions of year to normally happens. like the gran cayon in Arizona just to mention one. in the formation of the earth there were process acceleration. just like the creation of man. God made a grown man that at age of one had the characteristic of a man of 30 probably. same happened to the earth.
RE: Were the seven days of creation in Genesis seven twenty four hour periods? - Into the detail