In an introductory talk on geology, some 50 years ago, it was suggested to us that it would help if we were slightly mad to more easily understand the subject. I’ve never had a problem with that, but I have often wondered what was meant. I think it might have been that normal people have difficulties with two aspects of geology, both of which arise from our ridiculously short human life span compared with the time taken for geological processes to run their course.
Firstly, the Geological timescale is too long for us to assimilate, given our brief experience of passing time. The length of time that we can appreciate, even if we can grasp historical or even archaeological timescales, is too short to encompass the completion of geological processes.
A solution to this problem would be to ignore the measurement of time altogether. As long we had a sense of the order and the relative duration of geological events, that should be all that is needed to understand the processes involved. But we are not very good at dealing with continuums, we need to construct boundaries within them to form manageable units. In the case of time, we use dates, which leads to those difficulties with huge numbers.
There is a trick which makes it easier to relate the geological timescale to our timescale, which is simply to think of a million years as one year. This reduces geological time to a scale which is more easily assimilated.
The oldest surface rocks, found so far, are from the Nuvvuagittuq greenstone belt at Hudson Bay, Canada. These could be up to 4,300 million years old. So, using this trick, this age equates to roughly 2,300 years BCE. This is close to 2,500 years BCE when the upright stones were placed at Stonehenge, according to English Heritage, making it the familiar structure we know today, and it’s roughly when construction of the Egyptian pyramids started. This is probably the most distant time that most people can comfortably appreciate, so it is convenient to use that as a more accessible backstop in our concept of time.
Using 2,300 years BCE as our backstop, from a viewpoint in the year 2020, for convenience, some significant geological dates converted to a human timescale become:
- Earliest single celled life develops in the sea, about 3,500 million years ago = about 1,500 years BCE.
- “The Cambrian Explosion”, plants and animals begin to diversify and colonise land, about 540 – 450 million years ago = about 1480 – 1570.
- The Age of Dinosaurs, about 240 – 65 million years ago = about 1780 – 1954.
- Beginning of the Pleistocene glaciations, (Ice Age), and the evolution of the Homo group of Apes, about 2.6 million years ago = about 2 ½ years ago.
- Evolution of modern humans 300,000 years ago = about 4 months ago.
- Beginning of last glaciation, about 110,000 years ago = about 40 days ago.
- End of latest glaciation, about 11,700 years ago = 4 to 5 days ago.
The use of this condensed time scale makes it clear that the glaciations were a very recent geological event. When we look at the local chalk landscape, we should expect to see the scars of very fresh events which have not yet had time to heal.
The second problem with geological time arises when trying to understand the formation of landscape as a continuing process because it happens at an imperceptibly slow rate when viewed from our time frame. (We like to take refuge in the permanency of our surroundings; ‘as old as the hills’ is not a helpful analogy when trying to appreciate the effects of geological processes).
This problem is more difficult to overcome. It would be like trying to get a Mayfly, which flies for about a day, to grasp the concept of darkness, weather and seasons. The fly has no experience of these; its experience of the Earth is that it is a still, sunny, warm day in early summer. Likewise, we tend to assume that our landscape has been and always will be as we experience it now. But what we are seeing is analogous to one freeze-frame in a film. Unless we can see landscape as the product of a progression of changing environments, we can’t fully understand its formation.
It was the appreciation of the effects of an environment, which differs from the present one, that was key to the modern interpretation of the origin of chalk downland landscape (see the section on A history of ideas on the origin of Chalk Downland landscape).
Andrew Coleman
Rev. 04/01/2026
Geomusings 