Learning new geological terms at Scalloway

 

The BGS viewer names the rocks I found down the west side of Scalloway harbour, near the UHI, as being "granofelsic psammite". Turns out that psammite is the name for a generic metamorphosed sandstone and that granofelsic refers to its form or texture. It means it has grains visible to the naked eye that are fairly uniform. Now I thought I'd found a schist because it was quite shiny!

Burnt mounds on Shetland

The wonderful museum at Tangwick had an explanation for the many burnt mounds I kept seeing on maps. Apparently they date from the age before the existence of metal pans. I have seen Ray Mears in Canada use this technique to heat water in pre-metal birch bark pots that would burn up in a fire. Rocks are heated up in a fire and then placed in the water. The thermal energy from the rocks transfers to the water, raising the temperature of the water until the two reach thermal equilibrium. Repeated application of this technique broke the rocks and the broken bits were piled up - a burnt mound. I decided to try some data. Rock has a density of about 3 grams per cubic cm. A 10cm cube of rock would thus have a mass of 3kg. Granite has a specific heat capacity of about 800 J/kgK. A fire could heat the rock up to 500oC. Say that 5 litres of water, with a mass of 5kg, started at 10oC. Give thermal equilibrium as temperature T. Then 5 x 4200 x (T-10) = 3 x 800 x (500-T). I get T as 60 oC which sounds about right.

Uniform field : Tarmac's grave in Moffat

We visited McAdam's grave in Moffat. The crest had 3 arrows pointing downwards. Parallel arrows in a vector field show uniform field strength. This might be appropriate for his smooth road surfaces. 

Carbon storage on Shetland

 

This article says that liquid CO2 can be stored there before being sent down a pipeline to old oil fields to be sent underground.

Cyclopentane refrigerant

I saw this on the back of a fridge.

It turns out that cyclopentane has been used as a refrigerant to replace CFCs. It melts at -94oC. This is important because its temperature in the system will never be this low so it will not freeze in the pipes. Its boiling point is 49oC. The contents of the fridge don't heat it this high to turn it into a gas. Evaporation is achieved by compression and expansion to manage the pressure. The main reason for naming the refrigerant on the back must be that it is highly flammable if it escapes!

Looking for an igneous dyke at Galmisdale

 The BGS viewer showed a dyke below the camping pods at Eigg harbour. It is from the North Britain Palaeogene Dyke Suite - Basalt. I can't seem to find out much about it.

However, this rock on the side of the ridge of rock looks to have been baked. It is now very flaky. I'd say contact metamorphism.

And here are views of the ridge of rock I think is going to be the dyke.

Secret listening house on Bute

 There's a lone house in the distance down this road at Scalpsie Bay on Bute.

Here's what the interpretation board had to say about it.

This surveillance will be possible because each design of propellor will have slightly different types of movement and vibration. It is possible to identify the frequencies that make up a noisy complicated sound by the process of a Fourier transform to produce a spectrum showing the amplitudes of each component frequency. Each propellor will have its own distinctive spectrum. That's important because our own submarines go up and down past Bute too!