When I began studying geology, I remember my first-year lecturer telling us that we would “never look at a rock in the same way again.”
Before I started uni, I didn’t think much about rocks. They were just there, kind of boring grey or brown, sitting on the ground. But now I know that every rock has a story.
Many of my friends are geologists too, and so I have found myself in situations where I am on a holiday and someone spots a cool rock, and we all crowd around to have a look. These are moments I really enjoy, to be honest. Even though we all have a self-conscious laugh about how “you know you are with geologists when…”, it’s really nice to be able to share the appreciation with others.
When your companions are not geologists, the situation is quite different. This has happened a couple of times lately.
One time was last year in Japan. I was walking along a coastline with two companions (not-geologists) and I found myself looking at stunning volcanic sequences in the cliffs and rock platforms. After a little while, I said, “have you guys looked at the rocks you are standing on?” and was met with blank looks; “Uh… no?”
I tried to hold back from going into ‘overenthusiastic-geologist-lecture mode’. But when I saw this beautiful specimen (below), I couldn’t help myself.
My interpretation is that the big chunk of rock near my foot is from beneath the Earth’s surface. Then, magma came from even deeper, broke off the rock, and carried it upwards to eventually erupt out of a volcano. The eruption is explosive; the magma breaks into fine ash particles, forming a big plume, which then turns into a pyroclastic flow. (If you don’t know what that is, just youtube it. There’s some amazing footage out there. Basically it is a cloud of hot gas, ash and rock fragments that is too dense to stay as a ‘plume’, instead it ‘flows’ down the side of a volcano.) So, this chunk of rock that is now next to my foot either erupts out of the volcano first, or maybe it’s carried along by the pyroclastic flow. Either way, it lands in some soft sediments and punches down through them, and finer debris from the pyroclastic flow fills in the hole it made.
I’d say that’s a pretty dramatic and enthralling story. My companions listened politely, but didn’t display much excitement. Oh well.
I had a similar experience last week. I went on a three-day tour of the Scottish Highlands and the Isle of Skye. On our way through the highlands, we stopped for a photo from a hill. When I walked back to the bus, I noticed a road cutting and it looked interesting so I went over. And saw this!
Incredible! This is up there with some of the coolest rock I’ve seen. The dark parts of this rock are sedimentary – like a mudstone or sandstone. They form when sand particles settle at the bottom of a lake or an ocean, and settle into layers, eventually getting compacted into layered rock. The lighter coloured rock formed when magma cooled and solidified. So this was magma, and it has moved up through the Earth, and ‘intruded’ into the sedimentary rocks. It’s broken up these rocks, torn off chunks and moved into the gaps. This is a process that I have heard about since first year, but it is really cool to see it so clearly presented in a real rock. You look at this rock and you can see exactly what has happened to it. Scotland is where a lot of early geological discoveries were made, and I can see why!
When I went back to the bus, the tour guide said with a shrug, “yeah, I thought it looked cool, but I drive past it all the time…”
It made me wonder: why is history such a big part of tourism, but not geology? We visited about six castles on this tour, and heard stories of countless bloody battles. But to me, the story of magma rising from deep inside the earth, breaking up and swallowing the rock in its path, is kind of just as exciting. And to see that process ‘frozen in time’ and exposed in a rock face so that we can see it – well, I think that is pretty damn cool. Just as good as a castle, if not better. But maybe (definitely) I am biased.
So, to my geologist friends: thank you for sharing my enthusiasm! And to my non-geologist friends… well, thank you for putting up with my enthusiasm. (p.s. study geology – it’s awesome! And you’ll never look at a rock in the same way again!)