RE: Hadeicum; eon or era?

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu]On Behalf Of
> Hanneke JM Meijer
>
>
> Dear listmembers,
> My 12 year old sister is taking paleontology classes in school (the earlier
> the better!), but now she is asking questions that I have trouble
> answering..... Her first one was about the Hadeicum; whether this is an eon
> or era. I myself thought it was an eon, but she showed me some websites that
> say it is an era, and now I am confused too. Can somebody help me out on
> this one? Thanks!
>
> Kind regards, Hanneke Meijer

The Hadean is normally recognized as an Eon, as it is not part of any larger 
unit. However, it is not formally recognized by the
ICS. (Since the traditional definition of the Hadean is "that time after the 
formation of the Earth but prior to the oldest
recovered rock", it by definition cannot be part of the system that deals with 
the recovered rock record!)

                Thomas R. Holtz, Jr.
        Senior Lecturer, Vertebrate Paleontology
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
        Mailing Address:
                Building 237, Room 1117
                College Park, MD  20742

http://www.geol.umd.edu/~tholtz/
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796