Operation Iceberg

Operation Iceberg and other fun in Greenland - over the last few summers I have been working with a number of colleagues up in Greenland.  It's the best kept secret holiday location if you want stable weather, blue skies and 24hrs of daylight.  Rather than blogging here I have written a short piece for the "Travelling Geologist" - Chris Spencer - check out some of his great blogs on http://www.travelinggeologist.com/

richard 

Peering inside volcanoes: A guest post by Oliver Lamb

Picture yourself here. You are a scientist monitoring an active or erupting volcano. In the past, this volcano and others like it have produced lava domes which are prone to suddenly and violently explode or collapse to produce devastating pyroclastic flows, often without warning. Unfortunately, it's this sort of behaviour by Sinabung in Indonesia that recently took the lives of 14 people (see the video below for a spectacular example from Sinabung). So what can you, as the scientist, use to work out when the growing dome is going to explode or collapse next? What is already known is that the transition from quiet to violent activity during dome growth is because of a complex range of processes, particularly before explosions.

Fortunately for scientists like me, active volcanic systems produce a wide range of seismic signals prior to and during an eruption and these signals are easily picked up by seismometers deployed around the system. For my PhD at the University of Liverpool I am carefully analysing the seismicity from recent or ongoing dome-forming activity, focusing particularly on any signals that can tell us something about the conditions within the volcano before explosions or dome collapses. Hopefully by the end of this project, I will have looked at seismicity from at least four different active volcanoes: Volcan de Colima, Santa Maria, Mt Unzen and Mt. St Helens.

'Drumbeats' recorded over a 24 hour period at Mt St Helens, 15 November 2004

To give you an idea of the size of the dataset for this project, I've included the snapshot above of the seismicity from Mt St Helens during its eruption from 2004 to 2008. What you're looking at is the seismograph from a single day during this eruption, and each of those peaks is an individual volcanic earthquake. Now imagine trying to analyse each event, every day, every month,  for well over a year, then you have a gigantic number of events to look at! Thankfully, at least for my sanity, we have tools which we can use to automatically count all these events and measure different traits about each event. These traits include how big the event was, how long it lasted for, how long was it since the last event, the frequency content and much more. With these tools, we can now begin to track how these events change over time and begin to get a better idea of what's going on as the eruption progresses. I have already used the tools on seismicity from  Mt St Helens, and by my latest count the volcano experienced well over 500 000 seismic events from November 2004 to March 2006, an average of around 50 events per hour. I hope that emphasises how large the dataset is!

Left: Volcán de Colima, Mexico, during more peaceful times, taken August 2012.
Centre: Mt Unzen, Japan, nearly 20 years after it ceased erupting. (Credit: J. Kendrick, Liverpool).
Right: Santiaguito, Guatemala, taken December 2007. (Source: photovolcanica.com) 

But the project doesn't stop there. There are plans afoot for a whole raft of other analytical methods to be used. Methods such as locating each event as the eruption progressed, looking for events which may have come from the same source, and then some statistical analysis on top of that. Eventually, armed with all the geophysical results, my project will then begin the experimental phase. During the experiments, I will be placing samples into similar pressures and temperatures as we think the seismicity is being produced in, and break the samples apart and record the resulting acoustic emissions. The current idea is that by the comparing the experimental and volcanic waveforms, we can then help figure out what's going on inside the volcano during a dome-forming eruption.

The author, on the south flank of Volcán de Colima in July 2012

There you go, there's my project in short. For those of you who don't know me, I'm Oliver Lamb and I am a first year postgraduate research student with the Department of Earth, Ocean and Ecological Sciences at the University of Liverpool. If you have any questions or comments about what I've written here, then please feel free to get in touch with me via e-mail, olamb245@gmail.com, or find me on twitter, @olamb245. Thanks for reading!

Iceland - Orca 2014

Grundarfjörður

Iceland - Orca 2014

Iceland - a change of scene and most definitely a change in temperature since Tanzania!  I have spent the last couple of weeks working with the University of St Andrews Sea Mammal Research Unit (SMRU) on a project led by Dr Patrick Millar  investigating methods for measuring and monitoring the health/body condition of cetaceans, in this case, orca. 

Orca off the bow

Our part of the project will be testing sonar as a tool for specifically measuring body condition from body measurements.  This might seem like a far cry from mapping seabed or reconstructing palaeo-landscapes, the more usual deployment of sonar in my work, but really it’s not such a far cry.  The idea is to use a new generation of very high resolution sonar to map in real time the acoustic reflections from the body surfaces of whales as they swim past the boat or as we can manoeuvre the boat into a position to observe their habits such as feeding.  Ultimately, if we can obtain consistent and representative measures of body dimensions then SMRU might be able to observe aspects of body condition change during a season.

The sonar we are working with is the latest 3D sonar from CodaOctopus the Echoscope.  This sonar sends out a broad spectrum of acoustic energy about two, main frequencies, namely 375kHz and 610kHz.  The energy is recorded on an array in 3D that allows the reflected signal to be correctly positioned within a cone of insonification that is about 50degree in width and height.  With the addition of positioning and motion reference to the sonar, together with an insonification rate of up to 10 pings per second it should be possible to track the whales in real time.  What we are up here determining is if we can not only track them and thus ascertain their behavioural characteristics but if the sonar will also give us the resolution to be able to make precise body measurements.  This will require quite a bit of processing to first remove any noise in the data such as the fish schools that the whales are often hunting, the clutter from wave action at the surface and the seafloor.

SMRU boat Tango with Echocope fitted to starboard

So here we are in Grundarfjordur, on the Snefels peninsular with the team (Filipa Samarra, Sara Tauares, Miguel Neves, Fedutin Ivan, Olga Filatora, Sebastien Houillier, Paul Wensveen, Kagari Aoki, Julie Becsau, Jose Guilabert, Melanie Chocholek and Luke O’Connor) that will also be making a record of photo ID, sound recordings, tagging whales with motion sensors and taking samples for biopsy.  Why Grudarfjordur? Well over the last few years there have been large number of orca that visit the fjords in winter to feed on the vast stocks of herring that congregate in the still, cold and somewhat protected waters. 

The setting is spectacular with snow-capped mountains of layered basalts surrounding the fjord. Sure, its cold with frozen ground and even the snow at sealevel with an icy crust but that does not seem to daunt the Icelandic horses with their heads bowed to the constant north-easterly winds. 

Our mornings start with a check for orca in the fjord.  If there, and this is usually given away by the flocks of gulls and the odd eagle that flock above the feeding whales, then we launch the boat.  The sonar is deployed after making observations of behaviour in order that we can determine if the sonar is having a detrimental effect on the orca and then it’s a gentle approach to groups where they are feeding in order to obtain data.  On a good day we will get sonar data, photo ID of the whales and if lucky some biopsy samples. 

Image from Echoscope showing large male orca and young orca in background

Processing is going to take some weeks to obtain quantitative information but at the end of the trip we have managed to record some great data showing behaviour including groups working the herring schools up to the surface for feeding.

There is a great team here and it’s a real privilege to work on this project and in this part of the world – well worth a visit if you are interested in whales, outdoor scenery or of course for views of the northern lights!  Next time I must remember to bring my ice climbing and skiing gear for those days that the whales do not turn up!

Kilwa Marine Geophysics Survey, 2014

I have just returned from Tanzania working with Dr Ted Pollard from the British Institute in Eastern Africa and Elgidius Ichumbaki from the University of Dar es Salaam. Ted (also an honorary researcher at St Andrews) has been researching coastal archaeological sites along the southern Tanzanian islands near World Heritage site of Kilwa for over 10years.  His studies have documented settlements and trade back to Middle Stone Age with extensive developments from the 14C and 15C based on gold trade  that originated in modern Zimbabwe. To date, most of his work has been focused around recording intertidal sites in relation to the changing geomorphology that will have dictated the land use.  He has shown how river channels and harbours have silted up, settlements abandoned both as a result of nature and from human pressure.  There is a fascinating story in this coast line and one that despite the obvious immediate differences (its hot and the water is warm) has many similarities to the work that many of us are conducting around the North Sea.  

Kilwa Fort, Kilwa World Heritage Site, Tanzania

So this year Ted wanted to investigate the sub-tidal part of the study area.  In order to do this I have brought out our SwathPlus 468kHz bathymetric sidescan.  This is the sonar that we have been using up in Orkney, Scotland (see earlier posts) to successfully map the submerged topography (the drowned landscape) but also using to map different types of biological habitat on the seafloor.  It was deployed with a TSS DMS205 motion reference unit, sound velocity probe, Vector Hemisphere GPS and Topcon RTK dGPS.  Unfortunately here I do not have the advantage of bringing a custom survey vessel so we are relying on the collaboration with the Tanzanian Antiquities Department.  Check the video clip to see how the survey went and get a feel for the place. The boat required a fair amount of impromptu rigging and a couple of visits to a local woodworking shop - here my demands on yokes to go around the keel of a boat were a welcome change from making bed frames I think.

Charles Okeny from BIEA surveying using the SwathPlus bathymetric sonar

Over the course of the two weeks we managed to get a fair amount of the inner harbours covered including some great detail around the old fort and palace. Water depths ranged down to 65m and from the mapping it appears that there are a number of submerged coral terraces plus some great sediment features. 

As with any geophysics, it is only as good as the ground truth and so there was nothing for it here but to jump into the water to get some.  Whereas I am usually a fan of putting down an ROV (remotely operated camera) there was just not the facilities to do this and so we hired kit from a local dive centre and had to do the honourable thing – diving around coral reefs can be a hardship, honest!

The final map of bathymetry showing a deep (>60m) channel with steep coral shelf breaks

Dr Ted Pollard 

The result of the day of targeted dives proved out many of the sonar targets and gave some valuable information on seafloor type.  It also gave us the first confirmation of archaeological significance with a large pottery scatter at one site.  Ted will now be following this up with careful analysis/identification of the pottery.

Hominin footprints at Happisburgh (written by Dr Martin Bates, University of Lampeter)

View from clifftop looking towards the area of footprints revealed by the coastal erosion.

Well it is out there now after nearly a year of sitting on the news. The announcement last week at the British Museum that the world’s oldest footprints (outside Africa) had been discovered in Norfolk has made the news across the world. Again the small settlement of Happisburgh is in the news for the exciting discoveries about our Prehistoric past. From the BBC news to the tabloid newspapers, web media sites to blogs and tweets (even an appearance on Radio 4 Thought for the Day) the evidence is now available to all to examine. Our scientific findings were published last week on PLOS ONE and this shows that a small group of children and adults walked across the mudflats some 900,000 years ago. But how were these traces discovered? It happened last May when we were undertaking work for the British Museum as part of their English Heritage funded work to map the channels associated with the archaeological remains that exist beneath the cliffs of sands and silts laid down by ice sheets some half a million years ago.

Dr Richard Bates surveying area of footprints. Note the cliffs in the background are deposits (sands and silts) left by ice following retreat of the ice sheet that buried the surface with the footprints. Today the erosion by the sea is removing the sands and silts to reveal the deposits containing the archaeology and footprints.

We have been working on this project for the last 2 years or so and it was in the downtime while we were waiting for the geophysical equipment to take its readings that we saw what appeared to be odd patterns in the silts deposited in a former tidal channel. This system was probably part of the mouth of the Thames at that time. These traces were strange, elongated shapes totally unlike any of the natural ripple marks and mud cracks that occurred on other surfaces at the site. In fact they appeared very similar to features known from Holocene (last 10,000 years) sites in the Severn Estuary that had been identified as human footprints. We pointed this out to the archaeologists on the project and quickly a team was mobilised over the next couple of weeks to visit the beach to record these features and sample them for analysis. It is unlikely that these prints are the only ones preserved in the area and as the coast retreats further it is likely that more such surfaces will be exposed so the hunt is now on for more. Surprisingly there are no animal prints mixed in with the humans despite the fact the bones recovered from the site show a range of different animals were present with the humans. It has been hard to keep quiet about these discoveries for nearly 12 months knowing their importance but scientific rigor has to take precedent and that before announcing to the world their presence we had to be sure that these really were ancient footprints. Now we have the data and hopefully more will come to light when conditions are right to reveal them.

 

Close up detail of individual footprints at Happisburgh.

Chew Bahir, ERT 2013

I am just about to leave for Tanzania to do some offshore archaeological surveying with Ted Pollard from BIEA (I will be blogging on this on my return) but I thought before I went I would post a short video that was compiled during a field campaign late last year to the Rift Valley in southern Ethiopia. 

I made this trip together with Dei Huws (Bangor Uni) and Tigistu Haile (Addis Ababa Uni) as part of a much larger, international project that is drilling a number of locations throughout East Africa that are linked to key Hominid sites.  The overall aim of this is to be able to provide dated information about environment and climate at key stages of hominin development and migration.

The Chew Bahir site is located in SW Ethiopia close to the boarder with Kenya.  The large valley generally drains to the south into Lake Stephanie but the northern part where we hope to drill our core is only flooded on an infrequent basis.  As with many of arid areas, when it rains it does so often causing drastic and violent floods from the surrounding uplands that wash coarse river gravels far out into the generally flat valley floor.  Since our drilling objective is to obtain as simple a geologic sequence as possible the first task is to locate an appropriate site that has not been affected by the alluvial fans on the valley side or any of the ancestral rivers that migrate across the valley bottom. 

So, in November we made a preliminary field visit to the site armed with magnetic and electrical resistivity tomography/imaging (ERT) equipment in order to find appropriate sites.  Our choice of locations for the geophysics was based on some regional background work on geophysical signatures and also on some local knowledge kindly shared by Tullow Oil Plc.

The site is quite special and like nowhere I have worked before as you can see from the video.  We managed a couple of sites during our survey, one in the centre of the basin, the preferred core location, and one over an alluvial fan sequence at the edge of the basin.  The ERT gave some great results despite the arid conditions mainly I think because of the relatively high conductivity of the lake sediments – likely a result of the periodic wetting and drying. The alluvial fan was readily recognised in the ERT sections at the basin edge but no signatures of this were recorded at the centre of the basin where a fairly uniform sequence was modelled.

The next stage from us it to return to do a seismic reflection survey in order to image the top 400m (the core depth) in much greater detail. 

La Cotte de St Brelade

From Feb to Sept 2014 a new exhibit will be on show at the Natural History Museum, London that highlights some of the research undertaken by scientist in St Andrews and elsewhere in the UK as part of the Ancient Human Occupation of Britain project over the last 10years.  Britain: One Million Years of the Human Story presents key material and evidence from a number of important sites in and around the UK that help to document the dramatic story of changing landscapes and the people who lived in them over the last million years.  Two of the sites that this major exhibition showcases have been the focus of research for the dept E&E over the last 5years.  La Cotte de St Brelade is briefly described here, Happisburgh has been presented in a previous blog and will be the focus of a future blog as new results are published.

La Cotte from the sea

La Cotte de St Brelade in Jersey is a cave site that contains a 250kyr record of human use.  Investigations have been conducted at the site over the last 100yrs but there still remains much material that has yet to be uncovered.  It’s position however, on the shore in a highly vulnerable situation, means that much of the material is in danger of being lost forever and the site has been subject to intense recent study under a NERC emergency project.

A geophysical programme was initiated in 2012 to survey the wider palaeo-environmental context of the site.  This included high resolution marine mapping combined with geophysical modelling to allow the archaeologists to drain away the sea and literally step back in time to walk through the ancient landscapes. 

The palaeolandscape was surveyed using multibeam sonar aboard two research vessels, a 15m research yacht, Gambo and also using my inshore craft, the zego boat.  The resulting landscape model shows a complex valley system offshore, through which the herds of game would have been forced along routes leading up to the dead-end valley infront of the cave site.

 

Watch as sea rises over the submerged landscape of eroded granite terrain and then fly over the valleys up to La Cotte to get a view looking out from the cave

The new views from the mammoth butchery cave site are providing alternate context for understanding the prolific finds that have been dug from the site over the last century. 

 Work continues at the site and in 2014 we hope to start exploring the relationships between landscape, geology and the geology of tool assemblages from the cave.