Αυτό το οικολογικό σύστημα διαμορφώθηκε και λειτουργεί επάνω στο πλανήτη Γή εδώ και 4.5 Δισεκατομμύρια χρόνια!!! Ένα τεράστιο χρονικό διάστημα το οποίο ξεφεύγει κατα πολύ απο τα χρονικά περιθώρια που μπορεί να βιώσει ένας άνθρωπος με 80 χρόνια μέσο όρο ζωής.
Παρ' όλα αυτά με ένα απλό τέχνασμα μπορούμε να φέρουμε την αδιανόητη κλίμακα του Γεωλογικού Χρόνου (*), σε πιο κατανοητά χρονικά περιθώρια και να καταλάβουμε έτσι το μεγαλείο του Φυσικού περιβάλλοντος και τη θέση του ανθρώπου μέσα σε αυτό.
Ο Γεωλογικός Χρόνος και οι σχετικές χρονικές περίοδοι(Φωτογραφία απο το website του ODLIS)
Το παρακάτω κείμενο είναι απο το υπέροχο βιβλίο με τίτλο "An Introduction To The World's Oceans" των αδερφών Duxbury και Duxbury του οποίου έχω την τρίτη έκδοση αλλά έχει φτάσει πλέον στην όγδοη και διατίθεται απο τον εκδοτικό οίκο McGraw Hill.
"Very long time periods of time are incomprehensible to most of us. We often have difficulty coping with time spans of more than ten years - what were you doing exactly ten years ago today? We have nothing withi which to compare the 4.5 billion -4.6 billion-year age of the earth of the 500 million years since the first vertebrates appeared on this planet. In order to place geologic time in a framework which we can understand, let us divide the earth's age by one hundred million. If we do so, then we can consider that Mother Earth is forty-siχ years old, a middle-aged lady in whose past we have a strong and intimate interest. What has happened to her over that fourty six years?
The first seven years of her life leave no record; as she entered her eighth year a few fragments of her history can be read in some rocks of Africa and Greenland. By the time she was 12 years old the first living cells of bacteria-type organisms had appeared. Approximately ten or eleven years later, between ages 22 and 23, oxygen production by living cells began, but it took eight or more years, until about the earth's thirty-first year, to change the atmosphere sufficiently to support the first complex oxygen-requiring cells. The first fossils were laid down only six years ago, in her fortieth year, and by the time she was 41 the first vertebrates had developed. Eight and a half months later the first land plants appeared, quickly followed by an age in which the fish were the dominant life form. By age 43 the first reptiles, including the dinosaurs, had arrived, become abundant at the beginning of her fourty-fourth year, and dissapeared before her fourty-fifth birthday. A little over a year ago plants with flowers began to develop; four months ago the mammals, birds and insects became the dominant animal life forms. Our first human ancestors appeared twenty-five days ago, followed two weeks later by the first identifiable member of the genus Homo. About half an hour ago began the long process we know as recorded civilisation, and only one minute ago the Industrial Revolution began changing the earth and our relationship to her for all time."
Παραμένει καταπληκτικό, όσες φορές κι αν το έχω διαβάσει μέχρι σήμερα...
*Άλλη μια πολύ καλή τοποθεσία για περισσότερες πληροφορίες για το γεωλογικό χρόνο είναι η σελίδα της Σχολής Μηχ. Μεταλείων - Μεταλλουργών του Εθνικού Μετσόβειου Πολυτεχνείου.
