Fieldwork: Not just a geology holiday
As a geologist I often come across people who think my fieldwork is just an excuse to go relax in the sun while looking at the occasional rock. I can understand the confusion, why fly out to a different continent to study rocks when the department is already full of samples?
- The samples are biased Most non geologists and first year students will often wonder why we don't just look at samples, after all the department will be teeming with rocks collected by good natured researchers. Unfortunately, these samples are unrepresentative of a rock outcrop for two key reasons.
Firstly, the samples brought out to teach first year students will always be the simplest and clearest examples of that rock type. Most outcrops will not look like this but, for the purpose of teaching, these samples will help drum rules into the foggy mind of the hungover fresher/freshman better than an hour long lecture ever could.
Secondly, an outcrop’s geometry as well as its homogeneity (how much variation there is across the unit) tells us a lot about the environment of deposition, information that is lost in just a sample. Look at the picture below, its shows stacking elongate beds and actually indicates the direction in which a Jurassic reef was growing and therefore the direction of the open ocean. Pretty neat, huh?
- Fresh rocks are always better Each department will have a piece of halite that has become polished by the tongues of hundreds of freshers as they try to see if it tastes salty, potentially obscuring the rock fabric and making it harder to study. Fresh rock samples will always be able to tell you more than specimens that have been stored in rock drawers for many years. Whilst mapping I could identify one rock type based upon the strong sulphurous smell it gave off when fresh, while one of my lecturers can smell if a rock is dolomite. You also start to notice weathering patterns for different rock types, as well as identifying river systems by the characteristic channelized shape.
- You can predict what is under the surface Samples don’t let you take measurements such as dip and strike (the direction in which a bed is tilting and how much it is tilting by) as they are out of situ. By building up an idea of which rocks are dipping in what directions you can predict what rock units you would encounter if you were to dig beneath the surface. This is important in both hydrocarbon and mineral exploration as companies use surface outcrops to predict where to drill/dig their next hole.
- Rocks are rarely ever the same While it’s great that your lecturer has shown you what a fluvial sandstone will look like in class, I can pretty much guarantee that it will not look like that in outcrop. It is these differences that really make fieldwork important and lead to the idea that the best geologist is the one who has seen the most rocks. Only by going out and studying a range of lithologies in a range of localities can you start to build up an idea of what those brightly coloured diagrams are really trying to show you.
Some of you may still be thinking fieldwork sounds pretty easy, just moving from one locality to another to stare at rocks. Well when you factor in hiking up hills and scree slopes, scrambling over boulders and carrying a bag that can weigh up to 10kg (without samples) then it starts to seem less relaxing. Add to that the fact fieldwork continues regardless of weather (I have personally worked in minus conditions where the rain was so heavy you could barely see in Scotland to 40 degrees celsius at midday with no shade in Morocco) and it's starting to sound like hard work. Finally factor in walking several miles just to realise that your hammer/compass clino/gps is still at the last outcrop (conveniently at the top of the hill you just climbed down) and even a geologist may admit to having a bad time.
Luckily we tend to love the outdoors and obviously have a somewhat unhealthy obsession with the rocks we find out there. So just remember this; you can either let your resident geologist have their few precious weeks of fieldwork or you can endure them galloping off when on holiday to go and study a nearby exposure. Your choice.
Who am I kidding, we’ll still look at rocks even on holiday.
- Watson Image Credit: Watson
