Scarlett Geology 17th July 2021

Here I am, back on my beloved island after visiting family in the uk for 2 weeks. My first activity on Saturday was a guided tour of Scarlett with Dave Burnett from the Geological Society, and organised by the Manx Wildlife Trust. If you are planning a visit here, always check their website for events while you are over.

It was another gorgeous day. Fortunately, this was a morning walk and talk so we wouldn’t be exposing ourselves to the hot manx sun – I never thought I would see the day when I would be saying that!

We started by looking down at the beach beside the car park. That might sound uninteresting until you look at what is beneath your feet. The limestone is made up of millions of crushed sea creatures, so that most of the time you wouldn’t have a clue as to what the limestone comprises as they have completely disintegrated. But here, there is heaps and heaps of evidence of times gone by, of the mediterranean type of climate, balmy seas and coral reefs that once was our island. Now, we are talking a long time ago, something like 330 million years, but when you think that the world is 4.6 billion years old, it isn’t really so long ago. Look down at your feet and attune your eyes and you begin to see another world of fossils. This isn’t the place to get too excited. You won’t find any dinosaurs here, they came and went after this time, but what you will see are fossilised remants of crinoids and corals, some of which are massive. Then you can imagine swimming in a warm sea surrounded by these beautiful animals and coming out to a… gin and tonic? Maybe not, but it sounds good doesn’t it. The photos below show corals.

We then moved further up the beach beyond the Wildlife Trust Centre and noticed that the limestone has more folds in it than at our original location. We were also shown some dykes lying on fault lines, which are gaps in the limestone where molten rocks from deep in the earth had intruded at some point. This material is known as dolerite, but is softer than the surrounding limestone so only some deposits remain. We were told that what we see at the beach is just the tip of the ‘iceberg’ and that the dykes run for kilometres inland under the ground and also go deep into the earth. These faults are minor but together they form of patchwork of faults under the Isle of Man, but don’t worry, an earthquake is not imminent (I hope).

Only slightly further on, the landscape changes again, and the smooth limestone rock is replaced by lumpy granular rock, containing large and small black and brown pieces of volcanic rock and other very fine rock which is ash. This combination is called tuff, volcanic ash which is spewed out during an eruption. Dave explained that sometimes eruptions are more gradual and the rock comes out of the earth as if out of a toothpaste tube creating a pillow effect, called ‘pillow lava’; and at other times when there is more water in the mix it explodes rather than a can of fizzy drink, and this is what tuff does. There is plenty of tuff to look at here. You will also notice that it is a lot sharper than the limestone. If you want to see pillow lava you will need to go further along the coast towards Pooil Vaaish.

We moved on again, and Dave showed us areas where all the rocks have lots of holes in them – these are called vesicles. As the molten rock, water and gas comes to the surface it forms bubbles which, if they do not explode, get contained within the solid rock. These are similar to pumice, which is created by the same process but to create pumice the explosion is frothier creating a lot of light bubbles. In the photo on the right you can see another white substance called Amygdalite, which is a mineral that infiltrates the rocks after it has cooled. It is not quartz, which is found extensively on the island, but is more likely to be a zeolite or calcite.

Just while he was explaining all this a pod of dolphins decided to give us a performance, so he lost most of his audience for a while as they leapt about in the water. In any case, it was time to go. It was such an interesting morning, and it has inspired me to look into the geology in more detail. The photos aren’t great, but at least it shows the Risso dolphins were there. And I finish with a peaceful view inland from this same spot.