Sedimental #4 – Deep Time
Time for another dip into the soup of geological concepts that underpin the Jurassic Coast. This offering comes from Sam Scriven, Earth Science Adviser for the Jurassic Coast.
Deep time – not the time we watch tick by when bored. Not time measured with birthdays, seasons and celebrations. No. Deep time stretches backwards from our narrow ledge of existence into the previous iterations of our world. It is the kind of time where numbers become almost meaningless, where years melt into one another and the calendar is marked by the coming and going of species, by unimaginable catastrophes and by the slow passing of eons where change is literally galactic in scale.
Yet, in getting to know our Jurassic Coast, this is what we have to try and comprehend. There are many ways in which we might try to cram the 4500 million years of Earth’s history into a framework that is easier for us to understand. Something more intelligible to a creature whose consciousness is bound within a handful of decades. For instance, we might use a 24 hour clock to represent the ancient ages of the Earth, where the planet formed at midnight, life emerged at 4am, Dinosaurs ruled from 10.25pm to 11.40pm and humans only appeared in the last two minutes. Alternatively we could stretch out an arm, with the formation of Earth at our shoulder and the present at our fingertips, and consider how all of human civilisation could be erased from the scale by a swipe of a nail file. Or we could compress the millions of years into millions of seconds and imagine how the first humans appeared three weeks ago, dinosaurs during 2006, early complex life in the 1990’s and the first life in 1910 (the Earth having formed nearly forty years earlier in 1872).
These efforts may help us grasp an idea of what deep time is, but we can never know what it really means. In a way the coast itself is a better indication of this than any analogy, or manipulated time scale. The rocks themselves are a physical manifestation of the passing of years. Even superficial differences like colour can indicate profound environmental change and the fossils that are in those rocks tell us something of how life survived along the way. We should be grateful it did. We are the direct descendants and inheritors; a product of ancestors that survived generation upon generation stretching backwards through history to the farthest reaches of life on Earth and its origins as single celled organisms. So, while our exceptional rock record begins and ends within the Mesozoic, we, the people here to celebrate it, have a claim to a heritage that is global and universal to all life on our planet. The Jurassic Coast is like a picture book – a family album – recording just a fraction of the deep time invested in our species.
Since the red Triassic sandstones of East Devon were laid down our spinning galaxy has made a single full rotation. In that time the dinosaurs evolved and died out, the first birds took to the skies, mammals flourished and diversified and flowering plants came to dominate the world. As our solar system continues to fly, at 600km per second, around the galactic core, we can only imagine what is before us, lurking in the immeasurable depths of time that lie ahead.
by Sam Scriven
Jurassic Coast Earth Science Adviser
first published in J-Post edition 34, July 2014