Everything is connected. Absolutely everything. From the more obvious water cycle, to the less obvious carbon cycle, to the frankly astounding and mind-boggling fact that we are all made of stardust.
Simple, observable, everyday phenomena tell us an enormous amount about how the Earth works. For example, I found out during my study of Book 6: Exploring Earth’s History, where that yellowy-orange dust comes from. You know the stuff, it ends up on your car sometimes after it’s rained. That is dust from the Sahara desert, and it only appears after a big sandstorm.
Sahara dust makes its way to our cars
The fine, red dust is carried up into the lower atmosphere by the wind, and – if it’s fine enough, and the wind is blowing in the right direction – it is transported to our little island and deposited on our cars (much to the annoyance of my dad – it’s an abrasive dust, you see, and if you scrub at it the paintwork is damaged).
In the past, dust from all over the Northern Hemisphere was swept up towards Greenland and deposited on the ice cap in the fresh fall of snow. Millenia later, some of our more extraordinary adventure-scientists (I think that’s a reasonable title for them) journeyed to the Arctic and took samples from the ice.
These ice cores tell us, amongst other things, how our climate has changed over the past 140,000 years. They show us the peaks and troughs of temperature, give clues as to how arid or humid the climate was, and tell us about the chemical composition of the atmosphere.
All this comes from the presence of dust in ice, and the proportion of heavy or light isotopes of oxygen (that’s 18O or 16O) in the snow that fell on the ice-cap.
The oldest-known rocks on the planet
Another use for isotopes is in radiometric dating of rocks. The oldest rocks we know about are around 4,280 million years old and occur in Hudson Bay, Canada*. That’s not long after the Earth and the other planets of our solar system formed (about 4,560 million years ago). They are pretty rare; rocks tend to get recycled during tectonic activity.
Rocks are, against all probability and expectation, extraordinarily interesting. Not only do they provide humanity with gems such as diamonds and emeralds; they provide us with fossils. Look at the rocks next time you see a cutting by the side of a road. Really look at them. That layering, if you’re in an area of sedimentary rocks, is giving you a snapshot of the past. You’re looking into prehistory. There may even be fossils in there.
Connected to this geological time-line are deep-ocean cores – the sediments laid down by erosion and the dead organic matter in the seas. They provide another means of establishing a relative time-line – and it’s all calibrated by the radiometric dating of rocks.
The study of rocks gave us the cause of the last mass extinction, that of dinosaurs (and a huge number of other families) in the K-T event about 65 million years ago at the end of the Cretaceous Period and the beginning of the Cenozoic Era. It’s called the K-T event because scientists are awkward so-and-so’s: K comes from the Latin for chalk – “kreta” (for Cretaceous) and T comes from Tertiary (an obsolete – but still used to confuse us students – name for the Cenozoic Era. And here is where I feel old: I’m sure I remember reading in books when I were a wee lass the name Tertiary. Cenozoic is a new one on me).
So what did cause the extinction of the dinosaurs? It probably wasn’t one single event (and it’s pretty much agreed that the other mass extinctions were not caused by a single catastrophic event, but by a combination of changing conditions). There were two events that happened at around the same time, on opposite sides of the world: a 10km meteor smashed into Mexico (you can see the crater on topographical maps) and in India there was, over the course of a couple of million years, an episode of flood-basalt volcanism.
The consequences of a meteor impact are fairly obvious: shockwaves, quakes, but mainly the dust, debris and gases entering the atmosphere. This would only last for a few months; but a few months of starvation is all that is needed to knock a species to its knees. Or its tentacles, if it has no knees. In short, the knock-on effect would be enormous (everything is connected, you see).
Likewise, the volcanism across the world would have a similar effect in terms of gas and dust – but spread over a longer period. CO2 and SO2 levels would rise, increasing the global mean surface temperature (they’re greenhouse gases) – but at the same time, the dust in the atmosphere would increase the planet’s albedo (the amount of sunlight reflected back into space). So overall, the planet would cool, and the rain would be acid.
This had the devastating, but on the surface insignificant, effect of collapsing a population of plankton because it couldn’t photosynthesise. Of course, everything above it in the food chain suffered as well…
Although these events were natural, they should be a cautionary tale to us humans. Every action has consequences. A change to the atmospheric composition can have far-reaching effects; alter the pH of the sea, and the consequences could be devastating. We don’t fully understand how it all works yet; but we know that changing one tiny variable will alter a dozen more in ways that we can’t necessarily predict.
Everything is connected, and it can tell us an enormous amount about ourselves; our past, present and future; where we came from, and where we might go.
To those who say that science takes the mystery out of life: you are so wrong – if anything, it deepens it and whets the appetite for knowledge and understanding. And you are missing out on the adventure of a lifetime.
*The image of the Hudson Bay rocks was borrowed from here: http://www.daviddarling.info/archive/2008/archiveSep08_1.html. I thank the photographer, but will certainly remove it if requested!