Arthur’s Seat, Edinburgh

Edinburgh recently held a volcanology conference (VMSG), which is quite fitting seen as an ancient volcanic complex can be found at the centre of Edinburgh! The following photos are just a few photos from a  trip up Arthur’s seat whilst at VMSG…

Edinburgh from  Arthur's seat
Edinburgh from Arthur’s seat. This ancient volcano  existed around 350 million years ago in a period know as the Carboniferous.
Columnar jointing above the road on Arthur's Seat
Columnar jointing above the road on Arthur’s Seat. This feature forms when the the molten rock cools causing it to fracture in a regular pattern. The intersection of these fractures forms the polygonal columns. They are a common feature found in igneous rocks worldwide.
Columnar jointing above the road on Arthur's Seat
More columnar jointing above the road on Arthur’s Seat…
Arthur's Seat at sunset
Arthur’s Seat at sunset. I think this area is currently closed due to rockfall.
View from Arthur's seat at sunset
View from Arthur’s seat at sunset
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Oil Shale Experiment

Another stop on the trip to Scotland involved looking at the oil shale’s exposed beneath the Forth Road Bridge.

The Forth Bridge
The Forth Bridge

Unfortunately the tide was in meaning we couldn’t look at the outcrops we had intended to, but we did get to see some of the sand produced from these rocks.

The black sand here is fragments of the oil shale. Unfortunately the tide was in so we couldn't see the actual outcrop.
The black sand here is fragments of the oil shale. Unfortunately the tide was in so we couldn’t see the actual outcrop.
Oil shale sand beneath the Forth Bridge
Oil shale sand beneath the Forth Bridge

If you take some of this black sand and heat it up (we used a candle), it is possible to release the hydrocarbons in the rock. Nothing particularly scientific, but its a fun experiment to determine if the rock contains abundant hydrocarbons!

Heating up the oil shale
Heating up the oil shale
Smelling the hydrocarbons released from the oil shale
Smelling the hydrocarbons released from the oil shale

Hutton’s Unconformity at Siccar Point

In Geology an unconformity is a surface separating two rock types of different ages from one another. An unconformity represents a period of erosion or non-deposition in the sedimentary record, i.e. a gap or hiatus where we have no record of what happened.

Hutton's Unconformity at Siccar Point
Hutton’s Unconformity at Siccar Point

One such unconformity is Hutton’s Unconformity. The confusing part is that the name Hutton’s Unconformity is the name given to several unconformities identified by the famous 18th century Scottish geologist James Hutton. On a recent fieldtrip to Scotland we visited Hutton’s Unconformity at Siccar Point, but other unconformities identified by James Hutton can be found on Arran and near Jedburgh.

Hutton's Unconformity at Siccar Point
Hutton’s Unconformity at Siccar Point

When sediments (fragments of previous rocks) are deposited (settle before becoming a rock) they form layers of progressively younger material burying the older material. If a sedimentary rock is the correct way up the further up the rock you go the younger (closest to present day) it is.

At Siccar point we can see two distinct units rock, with the layers of rock (bedding or strata) in the upper and lower units being at different orientations from one another. This means that before the second (upper) unit was deposited the lower (older) unit was tilted and eroded, producing a gap in the geological record.

Sign at Siccar Point
Sign at Siccar Point

Unconformities are crucial to our current understanding of geology. They paved the way for us to consider deep time, that is essentially an appreciation of the fact it has taken a very long, yet quantifiable length of time for the rocks we observe around us to have reached their current situation.  For the rocks here at Siccar point that means; deposition of the older sediments, tilting of the older sediments, erosion, then the deposition of the younger sediments on top. This order of processes cannot possibly happen quickly!

Sign at Siccar Point
Sign at Siccar Point

Unconformities have also been used as evidence that the mechanisms governing the production of these rocks (and the universe) have, and always will operate in an assumption  known as uniformitarianism. Uniformitarianism is a counter (and more accepted view) than the opposing catastrophism, which implies that the Earth was created in a series of sudden short lived events.

View from Siccar Point
View from Siccar Point