Geology is something of an anachronistic science, constantly looking back trying to answer the question: What happened here?
Fortunately, just because we weren’t there doesn’t mean we can’t figure it out–if you walk into your living room and find a large yellow spot in the middle of your brand new carpet, it doesn’t take a PhD to figure out that Fido had an accident (and, if you know some of the environmental conditions, you may even be able to develop a testable theory behind Fido’s incontinence). Figuring out the unobserved past is part of what makes us human.
It also makes great television, or there wouldn’t be so many TV detective shows. And, really, geologists are just dirt detectives.
Geologists–or geophysicists, as it may be–are trying to piece together a coherent picture from limited evidence to make sense of the earth below our feet. Science, in general, is a lot like doing a puzzle…Except you don’t have the box to tell you what it should look like. And you are missing pieces. And some of the pieces you have belong to another puzzle. And your friend has some of the pieces but won’t share them. And the pieces you do have are faded. And you have to convince people to buy you a table so you can actually put the puzzle together. So…like a normal puzzle, but really difficult.
Anyway, geology deals with the Past, with a capital “P.” The time-scales we deal with are mind-boggling. Even the scale of human history is difficult to comprehend: thousands of years is no small potatoes from the point of view of a single human lifetime. But compared to Geologic history, human history is actually more like one tiny grain of salt on those tiny spuds. It’s pretty minuscule.
Before we drill down into the geologic past, though, let’s clarify the difference between Geologic History and the History of Geology (Future posts are going to cover both, sometimes even in the same post).
Geologic History follows the events that took place in the natural world to build the terrane and terrain we see around us today (and even some we don’t see today).
The History of Geology follows the events in human history that shaped how we talk and think about the Earth beneath our feet.
Geologists’ Time (The History of Geology)
The History of Geology is a human history, on human time-scales, and has been going on in some form for thousands of years. In the ancient times, “geology” as we call it today was perhaps better understood as “cosmology,” accomplished largely through creation stories, aided by a spiritual lens, and often focused on the origins of humans or peoples. The early “cosmologists” relayed stories that made sense of the (physical and spiritual) world around them.* Scientists since then have done much the same thing (largely sans spiritual lens), but have subjected those stories (we call them hypotheses) to experimentation, observation, and review.
This scientific understanding of geology developed separately in many places. The Greeks were the earliest to record their (semi-)scientific observations, and Aristotle, in his work Meteorology noted the large time scales that geology must comprehend:
But the whole vital process of the earth takes place so gradually and in periods of time which are so immense compared with the length of our life, that these changes are not observed, and before their course can be recorded from beginning to end whole nations perish and are destroyed.
Chinese, Persian, and Muslim scholars also all had early generalizable observations on the physical process that create landforms. These advancements were lost and rediscovered over the centuries, and developed into the earth sciences of today: a highly rigorous and regulated community of people attempting to uncover truths about the world beneath our feet and the worlds above our heads.
Geologic Time (Geologic History)
As Aristotle observed, geologic rhythms are played out on an entirely different cadence than a human life–as we now understand, the scale of millions of years. So, before your eyes start to glaze over with the big numbers of geologic past, let’s just use one simple example: the Quaternary (kwa-TERN-er-ee) Period. This is what many of the geologists in Illinois work with because the glacial processes that created Illinois’s surface landforms happened during this period. It is also the period that we are currently in.
The Quaternary period began about 2,588,000 years ago (or, 2.5 million years ago). For those of you doing the math, that’s about 172,500 Facebook’s ago. Or 63,000 original Star Wars’ ago. Or 10,500 United States’ ago. Or 1,200 Jesus’ ago. Or 570 Great Pyramids ago. Or 150 Lascaux Cave Paintings ago. It was a long time ago.
On the scale of millions of years, there are rarely changes abrupt and global enough to demand rigid classifications between geologic periods. This is especially true for really old periods where climate data is less reliable. The reason the Quaternary is said to begin 2,588,000 years ago is that the Earth began to undergo certain climatic changes that resulted in glaciers beginning to advance southwards (at least in the northern hemisphere). In terms of dating rocks and sediments, there was also a paleomagnetic reversal right around then.
So, to be clear, Geologic history is less about time and more about environment (though the oldest eras use arbitrary time). If it were about time, it would make more sense for the periods to be divided up every million years or 10 million years or 100 million, or a nice round number like that. Instead, we see semi-random times for these periods because they are based on the climatic, environmental, and geologic changes the Earth is experiencing at the time, reflected in various stratigraphic indicators.
Geologists can watch the “seasons” of the earth change by looking at the geology. As these “seasons” get older and older, geologists generally become reliant on fewer and fewer types of data. There are still important “golden spikes” defining the changes between erathems/eras, but they may be less precise or have less resolution. These seasons of geologic time create some confusing vocab terms: there is a difference between the rocks laid down during the Cenozoic Era (the “Cenozoic Erathem”) and the actual time indicated by the Cenozoic Era itself. But it does actually make the term “Geologic Time” make a bit more sense: we measure time by the geology we see.
Provisions from the Past
In contrast to geologic history, the History of Geology is the history of those studying geology. For the purposes of this blog, I’m also going to expand that to the history effected (and affected) by geology. I will be doing that in a series of posts that I am calling Prévenance, of which this is the first post (yes, “prévenance” is a real English word that means “the anticipation of others’ needs.” It comes from the same root as provenance and prevenient).
These geologically-effected histories are more powerful than I think most people realize. The fields of epigenetics and psychology deal with the idea that we are in large part a product of our surroundings. I agree, and add that the seemingly random distribution of geological features profoundly affects our collective and individual personalities, the way a society is organized, and the way we view reality.
Though the geologic rumblings of the past may be in the realm of unremembered eons, it shapes all aspects of our lives today. The geologic activity of this forgotten Past created the resources that sustain us today, as though all of (Geologic) History was in attentive anticipation of life as we know it–a prévenance from time immemorial.
*Note:
The first ten chapters of Genesis in the Bible, for example, are composed of rich narratives foundational to the Abrahamic faiths. These stories may be theological in intent, but they touch on (albeit, unscientifically) topics we now address in geology, hydrology, botany, taxonomy, meteorology, anthropology, animal husbandry, agronomy, mineralogy, and biology. The writer relayed how the earth came to be in language that he understood.
In fact, many religious writings that touch on how the world came to be are not scientific, though they touch on subjects addressed by science. Religion and science may inform one another, but they are not the same: just as you cannot theologize your way to Planck’s constant, you can’t science your way to a theodicy. This does not mean that the religious writings are wrong or useless, it just means they are not scientific. Science requires rigorous observation and experimentation to explain the physical phenomena in the world around us. Religion requires faith and actions lived out in a coherent and intentional manner.
If you want a fuller explanation of how I understand Genesis, check out The Lost World of Genesis One by John Walton.
Writing in Rock 