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Geological Time-Arm

Some time ago Callan Bentley collected a few nice geological analogies. I instantly liked one of those, found in the comments: earth history as a human arm.

Geological timescale, visualised with the human arm

Numbers: ages in Ma. Unlabelled yellow stripe: Cenozoic, Me. = Mesozoic, PalĂ€o. = Paleozoic, Proterozoikum = Proterozoic, Archaikum = Archean, Hadaikum = Hadean. Mark at 4280 Ma: oldest known rocks.

I think that the arm is a clearer illustration than e.g. using the “one year of earth history is one second” approach (where the age of the earth would be 146 years) or comparing it to the human life span. 146 years or your complete life are not so easy to visualise, in my opinion. Also, you can easily carry your arm around and show “You are here.” on it as necessary. 😉

Originally, the idea is from Thomas R. Holtz in his comment on Callan's blog:

Earth history as a human arm, with the contact between the neck and the shoulder being Earth's origin:

The shoulder is the base of the Archean.

The elbow is the Archean/Proterozoic boundary.

The wrist is the Proterozoic/Phanerozoic boundary (with the bulge of the lower forearm being about where the Ediacaran begins).

The palm is the Paleozoic.

The first two digits of the middle finger is the Mesozoic.

The last digit of the middle finger is the Cenozoic, and a single pass of nail file eliminates the history of Homo sapiens.

If you measure and calculate this, you'll recognise that geological time spans and body don't match well from Phanerozoic/wrist onward: The Phanerozoic should start only at the knuckles and the younger ages move closer to the fingertip accordingly. I have drawn it that way in my picture above – hopefully correctly.

Using my arm length of 85 cm, measured from the contact shoulder/neck to the tip of the nail of the middle finger, I get these figures:

Ma cm Age Event Place on arm
0.01 0.0002 (2 Â”m) Neogene end of the last ice age
0.16 0.003 (30 Â”m) oldest Homo sapiens “nail file”
17 0.3 formation of the 2nd Lusatian lignite
seam1		 near the edge of the fingernail
23 0.4
65 1.2 Paleogene base of the fingernail
251 4.6 Mesozoic first finger joint
542 10 Paleozoic knuckle
ca. 600 11 Proterozoic Deposition of the Lusatian Greywacke2 beginning of knuckle
1000 18 formation of Rodinia / Grenville orogenesis wrist
2500 46 elbow
3800 70 Archean contact between arm and shoulder
4280 79 Hadean oldest known rocks on the shoulder
4600 85 formation of the earth contact between shoulder and neck
  1. A lignite (brown coal) deposit that is extracted in large
    opencast mines in east Germany [↩]
  2. The oldest rocks found in my vicinity, e.g. exposed at the Koschenberg “mountain”, now a quarry pit. [↩]

Comments 6

  1. Lutz 2 ⟨  8 Nov 2008, 07:48 PM | #  ⟩

    Toll! Sehr schön umgesetzt 😉

  2. Silver Fox 7 ⟨  9 Nov 2008, 03:38 PM | #  ⟩

    A nice graphic - the arm and geologic history - I can read that part even without knowing German! Glad I spotted it.

  3. fj 232 ⟨ 10 Nov 2008, 12:06 AM | #  ⟩

    @Lutz: Schön, daß es Dir gefĂ€llt, und danke fĂŒr die Werbung. 😉

    Und ich hÀtte besser was kurzÀrmliges anziehen sollen, das Ellbogen und Schulter nicht so verbirgt.

  4. fj 232 ⟨ 10 Nov 2008, 12:05 AM | #  ⟩

    @Silver Fox: glad you liked it. However, I should have worn a short-sleeved shirt – elbow and shoulder are well hidden.

    Perhaps I'll do an English version of this later on.
    [Which is finished now – if you don't get it automatically, use the language switch (flags) at the top of the page.]

  5. Helmut Suttor 1 ⟨ 26 Feb 2010, 11:00 PM | #  ⟩

    Hallo,

    zu Ihrem Zeitarm: Ich suche fĂŒr einen 8jĂ€hrigen, der Steine sammelt eine einfache Darstellung der Perioden der Erdgeschichte. Das Problem beim Zeitarm wĂ€re vermutlich, dass die meisten Steine die man heute findet im Bereich Hand / Finger einzuordnen sind.

    Man brĂ€uchte also eine Darstellung, die den Bereich, in dem die Masse der heute vorfindlichen Steine zu einzordnen ist differenzierter aufschlĂŒsselt. Die Darstellung mit der Hand wĂ€re dann eine prima ErgĂ€nzung, weil sie die ganze Erdgeschichte umfasst.

    MfG
    Helmut Suttor

  6. fj 232 ⟨ 28 Feb 2010, 06:02 PM | #  ⟩

    Leider ist mir keine Ă€hnlich „greifbare“ Darstellung fĂŒr das Phanerozoikum bekannt. Man könnte dafĂŒr natĂŒrlich wieder den Arm verwenden. Dann wĂ€re der Beginn des Mesozoikums ungefĂ€hr am Ellbogen, das Kanözoikum beginnt bei den Knöcheln.

    Wenn aber die einzelnen Perioden/Systeme (z.B. Kambrium, Trias) dargestellt werden sollen, gehen einem irgendwie die markanten Stellen am Arm aus, bzw. es wird halt unĂŒbersichtlich.

    Ein Ziel des Zeit-Arms ist ja gerade auch, zu veranschaulichen, daß eben die Zeit, wo „viel los war“, die also viel Spuren bzw. Gesteine und Fossilien hinterlassen hat, ziemlich kurz ist im Vergleich zum Gesamtalter der Erde.

    Allerdings kann „die meisten Gesteine“ lokal recht unterschiedlich sein. Wer in den Mittelgebirgen oder Alpen unterwegs ist, wird in der Tat hauptsĂ€chlich mit palĂ€o- und mesozoischen Gesteinen zu tun haben, die sich dann auf den Fingern drĂ€ngen. Hier in Nord(ost)deutschland sind diese Ären eher selten, dafĂŒr findet man sehr viel proterozoische, 1 bis 2 Ga alte Geschiebe aus Skandinavien. Die wĂŒrden dann auf dem Vorderarm liegen.

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