Interactions between earthquakes and a ‘critically stressed’ volcano: the 2018 eruption of Sierra Negra, Galapagos Islands

This talk, bring me back to my 2nd year lecture of Natural Hazard in Seismic part of the course, glad I took the course and can use what I learnt then to understand and comprehend the talk. Basically, the speaker is highlighting the possibility of earthquake generation after the triggering event and the processes involved in that generation of the Earthquake using the data from Sierra Negra Volcano as example.

The nature of the dynamic triggering

The main question that I think people should listen to this talk to is
Which part of the earth is the most sensitive for the earthquake triggering and where  is the perturbation of earthquake most likely to occur for of course better understanding and also better forecast of the earthquake.

Processes that cause the interaction between the earthquakes and volcano eruption is quite well known in sense that we know how exactly the stresses change through the earth,

1) Dynamic stress changes
2) Static stress changes

The record on whether stress increasing or decreasing after earthquake can be recorded, but the background of the stress  is still not known and the area in which more susceptible of the stress changes is also can't be pin-point easily.

The dynamic stress changes as earthquake move away from the source of the earth quake govern by the surface wave which from the observation can last for few seconds or minutes, in very rare cases few hours.

In the allocated 30 minutes target time at Sierra Negra, the low frequency energy on seismographs, showing that arrival of big earthquake that happen with Rayleigh wave arrival earlier than surface wave with high amplitude with double dispersion. The amplitude gradually decreasing with time.
This high frequency energy must be generated locally and this is what correspond to the eathquake which trigger the wave. Earthquake is more likely to happen in the area with high dynamic stress changes.

The  first ever local record of seismicity associated with an eruption at a volcano in the Galapagos

Rate of the earthquake in the area is increasing showing that the volcano is becoming more seismically active and continue to inflate. The volcano in other way, is approaching a likely eruption.
And hence why it is suitable for the area to be the main focus for investigatin the relationship between dynamic stress changes and earthquake triggering.

There is good possibilities to be able to witness several triggering event of the volcano with the dense distribution of seismometer that allows accurate eathquake locating process. Opening a window to see the mechanism of the earthquake and what is the interaction processes between the dynamic wave with the local stress from the volcano for better idea on what controlling the dynamic triggering and how to identify them

The logistic part

Galapagos Island is a hotspot for volcanos because they belong to Ecuador. Dominated by big basaltic shield volcanoes with large and deep caldera system. Started in April and arrived in the island after 48 hours.Some areas are quite remote and some have very thick vegetation.

 I think this is very cool and interesting to participate in and the area sound very fun too!

Next post: Getting into the mechanical behaviour of sand with X-ray Tomography

The Geological Record of the Earhquake cycle in the lower crust

First of all, this is one of the seminar where I can really understand what the speakers actually wanted to deliver to the audience and it is without a doubt has succeeded in keeping me and others as well to focus on his topic.

The seminar is first started by giving the introduction to the audience so that the audience who might have and might have none prior knowledge in the field can understand.

Main Points and Results

The results in experiment trying to correlate the strength of the lithosphere and the stress that act upon it, show that basically the lithosphere is divided into 3 main mechanical zone.

1.       Shallow part of the crust where deformation took place in brittle style and the strength is dependent on frictional resistance

2.       Bottom part of the crust where lithosphere has plastic style deformation and the strength is determined by the plasticity of the mineral in the area

3.       in between the 2 layers where brittle-ductile transition took place showing major rheological discontinuity

Besides the layer based strength, the lithosphere is also affected by the presence of fluid in which the lithosphere is weaker when it is wet and stronger when it is dry.

Water, affecting or weakening the lower crust by three main mechanism

1.       Hydrolytic weakening as water facilitate the movement of dislocation

2.       Nucleation of new weak phases such as mica during metamorphic or hydration reaction

3.       Facilitate grain boundary diffusion and sliding

Earlier hypotheses that suggest the nucleation of earthquakes in the upper mantle is proved to be not true, it has been widely accepted that the nucleation of seismogenic record occurred in the lower crust. It is from seismological evidence of earthquake record with magnitude higher than 5Mw in Africa, India, China and Mongolia, peak at 15 – 40 km depth suggesting lower crust. The common characteristic of the four locations is that they are all have underwent dehydration as a result from partial melting and subsequence of melt removal with geological  record of tectonic Pseudotachylite.

Emplacement of Pseudotachylite enhanced the fluid blocking direction in metamorphism with consequence of partial transformation of Pseudotachylite to Eclogite. The Pseudotachylite provides necessary pathway for liquid. Shear zone and metamorphic reaction is consistently in line with large volume of Pseudotachylite. However, even with this observation, the deformation mechanism is still a mystery to be explored.

Investigation in other regions such as in Northern Norway shows that there is overprint pattern of mylonitic foliation of previous Pseudotachylite by newly formed pristine Pseudotachylite. This shows cyclical and repeating pattern, recording history between brittle and viscous deformation.

All in all, he arrived to the conclusion that the main deformation mechanisms are diffusion creep and viscous grain boundary sliding in mylonitized pseudotachylite. This basically highlighting the roles of lower crustal earthquake in providing path for fluid infiltration hence weakening the dry granulites. 

Next post: Interactions between earthquakes and a ‘critically stressed’ volcano: the 2018 eruption of Sierra Negra, Galapagos Islands

Date: 01/11/2018
Venue: LT 201
Speaker: Prof. Luca Menegon, University of Plymouth

Brain Evolution in rodents: What did our ancestor’s brain look like?

When I first get into this seminar, I was shocked as did not expecting too much of medical terms but of course it is impossible to talk about anatomy and brain without using this much of medical term. Hence, I think it is necessary for me to include some simple definition copied from any internet sources just for the sake of better understanding.

Neocortex: a part of the cerebral cortex concerned with sight and hearing in mammals, regarded as the most recently evolved part of the cortex

Endocast: the internal cast of a hollow object, often specifically used for an endocast of the cranial vault. Endocast can be manmade for examining the properties of a hollow, inaccessible space, or occur naturally through fossilisation.

Euarchontoglires: taxanomic superorder within Placentalia. This includes rodents and primates

Main Point

This interesting talk is about the journey of the brain evolution of mammal brain through time by comparing the brain of ancient rodent and its nearest relative now. The comparison of the brain anatomy and the functionality is basically the main focus of the research by Dr Ornella Bertrand.

Technique

The main method used is the CT scanned in order to obtain a virtual endocast of 11 fossils of primitive rodents; Ischyromyidae, 4 mountain beavers and its relatives; aplodontidae and 22 modern squirrels.

Results

The results show that the size of the brain in changing throughout the time. They have tried to relate this change with the change of body mass, but it is not correlate with each other.  There is no continuous increase in the changes occurred.  The hypotheses is the changes might be due to a change in locomotion behaviour. They find that species that spend more time on trees has higher EQ compared to species that spend time underground. This can be related to their vision in which much clearer and sharp vision as well as the amount of light hey are exposed to. More light exposure and sharper, clearer vision needed for the species living on the trees. As light is significantly less underground, vision might be less important for this species.

Importance and application

In conclusion, this new insight of the mammal brain evolution might have the same equation on the functionality and evolution of human brain. As human are now more exposed to use in technologies and wider opportunity to travel, this might have affected the brain as it has been proven from the research that brain of mammal does and can change throughout its lifetime timeline in response to the change of environment.

More on human brain evolution:
https://www.scientificamerican.com/article/how-has-human-brain-evolved/

Next post : The Geological Record of The Earthquake Cycle in The Lower Crust

Date: 25/10/2018

Venue: LT 201

Speaker: Dr Ornella Bertrand

A new view of seafloor spreading, 50 years on

Picture from : https://www.thinglink.com/scene/857449204946042880

I was rushing my way from central area to the King's Building to ensure that I did not missed the seminars. Ocean and its whole content has always amazed me since I was a child, look at that wide blue sea without limit, I can see the sky above it, the boats and ships making their way against the waves but I still do not know what is actually happening inside the ocean. How deep it is, does it even have a basement? what are they look like? what creatures can live in that? Is there even any life there? how deep are they?how is this whole amazing creation first started.

So this talk, given by Prof. Chris McLeod from University of Cardiff, might be able to answer some of my questions.

Here what I have summarized from the talk.

Main Points

2/3 of the earth is covered with oceanic crust but the knowledge on the seafloor is undeniably limited as it is indeed very difficult to reach and get “hands-on” on the sample of the seafloor, unlike the continental surface. Most of seafloor maps are obtained by the satellite.

  

Ocean crust, as known has its own life cycle of being continuously formed and then destroyed in couple of hundred million years period. In mid ocean basin, with mid ocean ridge as the centre, oceanic crust is continuously generated as result of plate diverging due to plate tectonic motion, accreting new materials into the mid ocean ridge.

As seafloor spreading involve movement, it is best to note that the rate of the spreading varies in different places. As example, spreading rate in the Pacific is the fastest and the slowest at the Atlantic Mid Ocean Ridge.

How much do we actually know about Oceanic Crust compare to our knowledge of the Continental Crust?

Seismic studies show that Oceanic Crust is different than Continental crust. The large-scale seismic experiment resulted that the Moho of Oceanic crust are very much shallower than the Moho of that continental. In correspond to Moho Reflection, the seismic structure of oceanic crust is shown to be very regular. Based on geological interpretation from ophiolites and drilling, the ocean crust is actually a layered structure with additional seismic layer 1,2, and 3 with intermediate velocity causes increase in the typical mantle velocity. This is same everywhere, the oceanic crustal structure remains regular regardless of the spreading rate, thickness and the age of the oceanic floor. The characteristic succession above mantle are sediments, pillow lava, sheeted dyke and gabbro.

Pieces of oceanic crust that have been obducted onto the continental and have been widely studied is called Ophiolite. The thing is even with detailed study of ophiolite, it is actually not telling the complete story or knowledge of the seafloor. The question started again when serpentinites are commonly found with ophiolite. 

How does this mantle peridotite rock can be found in the seafloor?

Attempt of summarizing faults information has been made but does not explain the answer to the question. There are peridotites found in the seafloor with massive lava flow directly on top of it with no crust, no stretches and no faulting.

The velocity decreases linearly from peridotite to serpentinite of ~8km/s and ~5km/s respectively. This explains why the seismic layering does not always work in processing geophysical data of the seafloor.

This again leads to more question on how regular oceanic crust structure actually is? How much does it was affected by spreading?

Several attempts to get closer to the sea floor

In doing this, the biggest challenge is the realisation that getting the direct access to the sub surface is very difficult near to almost impossible. One of it is the very expensive submersible that can only sample the surface of the seafloor. Following that is the idea of drilling the Mohole through the oceanic crust to the mantle but they only able to get into 13.5 m of the seafloor. The next attempt in the Pacific Ocean only get through the crust after 8 month which seriously cost millions.

Techniques

In was not until after years of planning that in International Ocean Discovery Program Expedition 360 that scientist decided to drill the Moho at the slower spreading ridge which the nature of the Moho here is significantly shallower due to removal of upper crust by faulting.

Results

One of the key finding is the existence of weak talc which shows that there is fluids role in converting peridotite to talc and serpentine. The importance of serpentinization mechanism is that to see the totally different mechanism of both strain localisation and weakening of the crust. The weak talc allows slipping. A few suggested mechanisms involving fault has been suggested; longer fault? Continuous fault? steep fault which the flattened? Detachment fault model might be favourable in this discussion as the speaker explained that this detachment fault is pulling one side of the plate while the other side move by normal plate diverging mechanism. Slow spreading ridges is significantly form by detachment fault which catches more than half of the separation materials. There are some relations of the targeted place with earthquakes where the targeted areas are actually active earthquake spots.

Conclusion and impact to us

There is more and more knowledge to be discovered by making the best out of the advancement of the technology.

Next post : Brain Evolution in Rodents: What did our ancestor's brain look like?

Date: 11/10/2018

Venue: LT 201

Speaker : Prof. Chris McLeod, Cardiff University

Mineral storage of CO2 in basaltic rocks Seminar

Picture is taken from: https://www.zmescience.com/science/co2-turned-into-stone/

When I first started my degree in Geology, one question has always remained in my mind for quite a while, what do I actually wanted to do when I first get into Geosciences field?

The biggest question that remained unanswered until today. I have had quiet a love and hate relationship with my degree, like honestly who doesn't right? There is time when I feel like giving this up and doing a completely new thing, trying something different. but the thing is, it is not myself to not finishing things up.So I decided that whatever is going to happen in the future, let it be, first thing first is finishing what I have already started, this degree.

After dwelling myself, observing others, reading the news, papers etc, something just ignites my interest in Carbon Capture. I can say largely it is due to my third year course, Petroleum System, where there is one part in which I have to read papers about the Scotland Carbon Capture and Storage and I find that really interesting and somewhat, what this entire world is really in need, a better environment. And carbon capture remained the biggest contributor for solving this at the moment.

Main Topic
So, I decided to attend the talk from Dr. Sandra from Reykjavik Energy. where she talk about new finding in Iceland where instead of storing the carbon captured or produced from the power plant in sedimentary rocks, they store them in basaltic rocks as Iceland is basically made up of basaltic rocks. hence, they have quite a large storage stocks.

Techniques and Results

To the surprised of everyone, the first process of CO2 injection into the basaltic crust have mineralised about 95% of the CO2 in just two years time when they initially thought the process will take up hundreds or thousands years of times. This has shed the light and new hope in reducing the Carbon content in the atmosphere. In the same time, new questions arise, how much CO2 can be stored by Iceland? I'll leave that for us to together think about this

After their pioneer project in 2012 shows applauding results, in 2014, CarbFix,started their industrial scale project and later joined with ClimbWork in 2017 for better financial condition. As of 2018, CarbFix 2 project is on its way where they planned to use seawater for the injection.

Important

This talk is basically opening a new door possibilities for a better environment. Let's all hope and make effort together to ensure the environment that will be passed down to the next generation is in its best condition.

More info on this can be read;
https://www.zmescience.com/science/co2-turned-into-stone/
https://www.sciencenews.org/article/volcanic-rocks-help-turn-carbon-emissions-stone-%E2%80%94-and-fast

Next post : A New View of Seafloor Spreading

Date : 04/10/2018

Venue: LT 201

Speaker: Dr Sandra Snæbjörnsdóttir from Reykjavik Energy