The Jurassic CREEP at Kilve beach
In the wake of the successful field trip in Cap de Creus held during the previous meeting, the initiative has been proposed again for the 3rd Short Course in Bristol with an excursion at the Kilve’s “delightful shore”, to cite the words of the famous poet of the 19th century W. Wordsworth.
Fig. 1: Breath-taking panorama at Kilve beach: layering of carbonate mudstones and black shales. In the inset: close- up of ammonite fossil in mudstone
Apart from being a breath-taking landscape, there is a lot of geological interest at Kilve: the cliffs are made of black shales interlayered with brown, yellowish and grey fine-grained carbonate limestone deposited in the lower Jurassic (Lias), in which beautiful fossils of ammonite can be found (Fig. 1).
The colour alternation marks a periodic change from an anoxic to a more oxidized depositional environment: the formation of widespread shallow seas following the supercontinent Pangea’s break up created the perfect conditions for the deposition of carbonate mud, whereas the presence of black shales is interpreted to be the result of episodic restricted water circulation in shallow marine basins that led bottom water to become oxygen deficient.
Fig. 2: Sets of differently oriented hydraulic fractures in carbonate mudstone
Moreover, owing to the burial of sediments and subsequent compaction, the pore water pressure reached the same values as the rock pressure, cracking up the lithified mud into two differently oriented sets of fractures (Fig. 2). This confirms that episodic gravity-driven fluid migration occurred and suggests that the orientation of the principal stress may have changed over geological timescales.
During the excursion, a separate chapter was dedicated to Kilve’s black shale. As a matter of fact, the hydrocarbon field at Kilve is huge: it was estimated it contains about 10 billion tons of hydrocarbon-bearing rocks! The trouble is that the dark colour of the shales is given by the presence of Kerogen, a bituminous material capable of yielding petroleum products via distillation, which is a very expensive operation to perform. This is the main reason why the idea of Kilve’s black shale exploitation as a mineral resource was discarded.
This field trip was therefore a unique opportunity for us to apply the fracture mechanics principles assimilated during the morning lecture directly in nature, to have an introduction about the seismic anisotropy a fractured rock can exhibit, and to have a good time altogether, bearing in mind that maybe Kilve beach is not the best place to light a barbecue, considering the amount of hydrocarbon in there!
Fig. 3: Mike Kendall (white helmet on the right), James Wookey (wearing an orange helmet on the left) and the CREEPers.
Discovering Bristol through the history: SS Great Britain and the Suspended Bridge
The choice of Bristol as a location for a CREEP short course was really spot on: after the daily lectures and practicals, we found enough time to dive into the suggestive history of one of the most important British cities.
Fig. 4: CREEPers and professors delighted by the history of the SS Great Britain told by a former member of the ship’s crew (red jacket)
For instance, we had the great honour to dine at the Brunel’s SS Great Britain, the world’s first great ocean liner, in the same place the ship was built, namely the heart of Bristol’s Harbourside.
SS Grain Britain’s extraordinary capacity (it could host more than 700 passengers as well as their horses) combined with the revolutionary technologies employed to build it, made it worthy of the title of “the greatest experiment since the creation”!
All these information and much more were passionately brought to us by a sailor in the flesh, who was accustomed to live and cut through the seas in the 3rd class of this legendary ship (Fig. 4).
Fig. 5: In the dry chamber. A close-up of SS Great Britain’s hull and the dehumidification machine “Deep Thought II” used to lower the relative humidity down to 20%, like in the Arizona desert, or like in the lab dry rooms!
One of the most astonishing stories for us as scientists concerned the approach used to preserve the ship and prevent corrosion due to the threatening action of water/brine and air humidity: the hull of the ship was sealed in a huge dry chamber in the same fashion we use to conserve our samples susceptible to air moisture like salt (Fig.5).
SS Grain Britain is just one of Brunel’s engineering masterpieces. However, the most famous was for certain the suspended bridge, which is the symbol of the city. The latter was commissioned when he was only 24 years old, witnessing once again his creative genius (Fig.6).
Fig. 6: The CREEPer Angelo enjoying the good weather after the daily session of lectures and practicals. In the background, the famous suspended bridge, symbol of Bristol
To conclude, there are many other places in Bristol that we didn’t mention in this article but that absolutely deserve to be visited, like the Wills Memorial Building that currently houses the school of Law and the Department of Earth Sciences, the gothic cathedrals, the numerous piers and navigation locks associated, but also the pubs scattered all around the city … Seeing is believing!
Lecture in 5th grade geography class – Secondary school in the Netherlands
Elenora explaining the various possibilities after high school
Right before the short course in Bristol, one of our CREEP fellows, Elenora van Rijsingen (ESR6), went to her former secondary school in the Netherlands to give a lecture to the 5th grade geography classes (students 16-17 years old). She wanted to teach the students something about science in general and about earthquakes (the topic of her PhD), but also show them what it is like to study (Earth Sciences) at university and how it is like to be living abroad. Since she graduated herself from the exact same school only 6 years ago, she is a good role model for the students.
As a first part of the lecture, she explained the students about her motivation to study Earth Sciences at the University of Utrecht. Because the next step for these students is to go to university, they discussed about the university system and all the possibilities there are. Following that, they learned what it means to be a PhD student and how to become one if they would want to.
Finally, they also discussed about plate tectonics. Elenora discussed beforehand with the teacher of the classes about the level of the students, so that she could adjust her story to that. She talked with the students about the different types of plate boundaries and how these are related to each other. Because she is studying earthquakes in particular, they also discussed the mechanism of an earthquake (and a possible accompanying tsunami).
Geography students during the lecture
In the end, according to the teachers, she not only managed to inspire the students to start thinking about their future, but also the teachers themselves to create more interaction with former students who could act as role models and show the current students all the possibilities there are after secondary school.
Installing seismometers – AlpArray Bavaria
Another outreach activity done by one of our ESR’s was the trip to Bavaria (Germany) by our ESR11, Angelo Pisconti, who went there to participate in the installation of part of the stations belonging to the seismic network of the European initiative AlpArray (http://www.alparray.ethz.ch/home/).
Site locations of the installed seismic stations
As we know, to advance our understanding in natural and induced seismicity is one of the main objectives of the CREEP project since this helps us to study the deformation and the rheology in the Earth. Consequently, the recording of the seismic signals is essential to carry out our research. Such signals hold information not only about the seismic source that triggered the earthquake but also about the variations in composition, temperature, and deformation along wave path, that is, in the Earth’s interior. Since seismometers are responsible for detecting and recording the seismic waves, increasing the number of seismic stations in the planet is necessary for increasing our knowledge of our planet structure.
Angelo in the field, together with Januka Attanayake
For this reason, getting experience in installing seismometers is a precious and valuable knowledge for Angelo, which research focuses on better constraining rheology and mantle flow patterns in the lower mantle using seismology. And what better way to get such expertise than collaborate in international seismometers’ deployment, like the AlpArray project. One of the actions of this project is to increase the seismic network of Alpine Area to collect top-quality seismological data in order to advance our understanding of orogenesis (mountain building processes) and its relationship to mantle dynamics, as well as the relations between plates reorganization, surface processes, and seismic hazard in the Alps-Apennines-Carpathians-Dinarides orogenic system.
As Angelo explains us in his publication on the ‘Outreach’ section, installing a seismometer is not a small thing. Choosing a site with little noise, levelling and coupling the sensor to the ground, synchronizing and linking it to a GPS sensor, providing the necessary energy to maintain the station and, finally, checking that the signals are stored in the memory card is a task requiring extensive experience and accuracy.
We hope that the adventure of leaving the office for a few days and go to southern Germany with his colleagues to install seismometers has been a useful and enjoyable experience for him.
Piercarlo, Beatriz and Elenora
