Ardnamurchan lighthouse and supermarket chillers

 The white spot in the middle of the picture is Ardnamurchan lighthouse seen from the Isle of Eigg. Two close flashes and then a long pause...

I found this claim on the chiller door of a supermarket

This article quotes a power of 72W. 72 Joules per second. The seconds in 26 years are 26 x 60 x 60 x 24 x 365.25 = 820 x 10^6 s. Multiplied by 72, you get 5.91 x 10^10 Joules saved. It is not clear whether this is for one unit of the chiller or not. 5.91 x 10^10 J divided by the number of seconds in a year gives 1.9kW of saving.

Thinking about volcanoes on the Moon

 

The dark patches on the Moon are called Seas. The Latin word is Mare. They just looked like that to the first astronomers. Turns out that they are basalt lava flows that are darker because they are more iron-rich and thus less reflective. It got me thinking about volcanic activity on the Moon. I had never thought about the internal structure of the Moon. It turns out it does have a core and a structure that is very similar to the Earth. Lots to learn here!

Looking for greywacke at Linn's Tomb

 The tomb of the Covenanter Alex Linn is a beautiful place. The space was filled by fragrant primroses.

There was an exposure of ground rock nearby. The BGS viewer says that the bedrock is Kirkcolm Formation Wacke. Chasing it back, it is part of the Caradoc Series, which is a set of Ordovician sandstones laid down on the floor of the ocean. The rocks are grey and quite gritty. It seems the series was named after a hill in Shropshire. Now to find the Coniston limestones which are an upper part of this Caradoc Series ...

Schiehallion beer!

I couldn't resist this and it was really rather pleasant. So I thought finding out about specific gravity might be appropriate. It turns out specific gravity is actually the relative density ie the density of the brew divided by the density of water. That is more complicated than it sounds because water has different densities at different temperatures. Since it is a ratio, I'm not clear whether that is affected by the temperature or not. Specific gravity measurements are used to calculate the alcohol concentration of the beer. Since specific gravity is a ratio, it has no units.

Back on the beach 360 million years later

 The sandstone on the south-west end of Bute is remarkable.

There are whole large quartz pebbles in the matrix. This sandstone is supposed to be 360 million years old. Now modern weathering is releasing the pebbles back onto a beach. It's been an interesting ride. Started in the mountains and eroded, carried by a river to a beach 360 million years ago. Then part of a bigger sedimentary rock trapped underground for 360 million years. Now back on a beach to continue being broken down. A real twist in the usual rock cycle story. 

Different sandstones at Hawk's Neb

 This is the Hawk's Neb formation on the southern end of Bute. Different layers in the sandstone are very clear. 

Close up, some of the layers are reddish and some are almost white. I had heard of there being a calcite-type stone called "cornstone" and wondered whether it could be that. 

Close up, the white shows that is probably just an over-abundance of quartz grains. Maybe this was an era when a lot of quartzite Dalradian hills eroded. But quartz means it isn't cornstone.

The red sandstone is clearly more granular. The grains look angular which I think might mean laid down in water. I need to find Penrith sandstone to see what air-blown grains look like.

The Haystack at Scalpsie Bay on Bute

 This remarkable feature was once a sea stack but the sea level is now lower than it was and so it is high and dry. The former sea cliffs are behind.

What makes it totally remarkable is the nature of its composition. It is a type of conglomerate that seems to include whole slates. It doesn't look natural! This rock isn't like any of the others round here. No one knows exactly how to age it. It could be Old Red Sandstone or it could be Permian - quite a difference of over 150 million years and opposite sides of the Equator!

DekaNewton and kiogram-force on an electromagnet

 There was an electromagnet operated by a keypad on the door.

I was interested in the label "300 daN".

Turns out daN stands for dekaNewtons 1 daN = 10N. I was thinking that it was simpler to write 3000N when I came across the idea of kilogram-force. On the surface of the Earth 1 kg mass has a weight of 10N to 1sf due to gravitational attraction. So by writing 300 daN, I assume that means that it could support a load of 300 kg pulling downwards on it. That quite a few of me. Sideways, the max load appears to be 100 kg. DekaNewtons are used to make an easier force to mass conversion under surface gravity on Earth.

Columnar Sandstone on Bute

 

This was an unexpected marvel at Kilchattan on Bute. It seems that one of the numerous igneous intrusions baked the sandstone which then cooled the same way that basalt cools into hexagonal columns.

Having another go after 360 million years

 

The Old Red Sandstone at the southern end of Bute is amazing. It contains large pebbles which are Dalradian and were eroded from mountains north of Bute 360 million years ago. They are quite rounded. They must have sat on the beach back then but ended up fused into the sandy matrix and turned into stone. Now erosion on a later beach is releasing the pebbles which are free again to be weathered and turn to sand. Geological time scales are mind blowing.

Medical physics

There are a variety of isotopes used in medical physics. At one end of the scale, Technetium-99m has a half-life of only 6 hours so it has to be produced where it is going to be used.  Cobalt-60 has a longer half-life of 5.27 years so can be manufactured centrally and distributed to where it is needed.

Moon rocks

Looking for information about features on the Moon, I was pulled up by the idea that I shouldn't be calling it geology, because geo refers to Earth. Some people use the term selenology instead. A first look at it is here. 

Carbon negative

 

This ice cream was the first place I'd ever seen the term "carbon negative". Apparently it means that a company is removing more carbon dioxide from the atmosphere than it puts in. Microsoft have set a goal of becoming carbon negative by 2030. It must surely be the case for the vast majority of businesses that they are paying some other firm that is involved in tree planting or technologies designed to remove CO2 from the atmosphere. Use of a search engine pulls up a lot of such companies.

Craters on the moon

Not the best picture of the Moon last night but the Tycho crater was very prominent. It has a very clear ray system spreading out. I could see clearly several other nearby craters silhouetted against the dark edge of the Moon. This suggests that these could be some of the ones formed when large lumps ejected by the impact came back down close by. It says that Tycho is a reasonably recent crater. If the impact had been visible from Earth, it would have been when yesterday's Purbeck Marble was still living snails!

Purbeck Marble

The sign above at Corfe Castle tells you what you need to know. This limestone is made of marine snails and can be polished. Not a true metamorphic marble but it can be polished. What really struck me was that it is from the Cretaceous period. That means it is about 200 million years younger than the Carboniferous limestones round here. In that time, Britain has drifted north and gone through the period of desert climate that resulted in the brockrams of the Eden Valley.

In Wantage Parish Church I came across two effigies of knights which showed that the Purbeck Marble can indeed be polished.

Institute of Physics i the Daily Star

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