Day 18, 19, 20 and 21 - Finishing off and heading back to Tenerife

So the last two days of sampling are here and they were both shorter days as we had made good time in the last week, covering areas with time to spare and both days went off without any major hitches. The last day I was on soil gas sampling and although nothing went wrong with the day, all but three sites were very difficult to sample from, indicating poor permeability of the soils we were sampling from.

The main geological feature observed on the last day were by the coast and consisted of many fine layers of fin e ash - airfall deposits.

Finely laminated airfall deposits

The day has finally arrived. Though the ferry is tomorrow morning, we are leaving today. Luggage packed, equipment packed, samples packed, house clean and off we go. We are heading to Santa Cruz, La Palma's capital, where the ferry back to Tenerife leaves from at 4am tomorrow. We are taking the long way round by taking the road over the north of the island via the geochemical station in Tazacorte. 

The road takes views over Tazacorte and parts of El Paso, it has been cut in to the Taburiente strato- volcano and passes through some spectacular pyroclastic deposits that contained evidence of base surge sedimentary structures. 

The road became quite 'zig-zaggy' with some very tight corners to get around, but it was well worth it. We pulled in to the car park at the top and went for a very short walk to see the caldera over 2000 meters below our feet, we were down there collecting samples just a week or so ago! Roques de Los Muchachos, the highest point of La Palma.

The highest point on La Palma

A beautiful clear day, again above the clouds, we could see Tenerife, La Gomera and El Hierro. Much closer, peering through the clouds we could see our filed area, Cumbre Vieja. 

From the top of Roques de Los Muchachos with Cumbre Vieja rising above the clouds over my left shoulder

A little cheeky Dream Team selfie at the summit (front to back: me, Samara and Hannah)

Also at the summit is the IAC; the Instituto de Astrofisica de Canarias. La Palma is known for its perfectly clear night skies perfect for star gazing and galaxy hunting.

Just a handful of the IAC telescopes

Well the time has come to say good-bye to La Isla Bonita. La Palma you are truly beautiful and magical and I can't wait to come back. But for now it is Adios!

The 4 am ferry called at La Gomera and on approaching Tenerife we were greeted by a sunrise over Mount Teide.

Sunrise over Teide, she looks so small!

We have today off and due to a tyre blow out, so do the Tenerife interns, which is great as we can have a day of catching up. This does mean however, they have to go out in to the field to complete their sampling tomorrow, so we had an extra day off - much needed after pretty much travelling through the night and getting next to no sleep for the best part of 36 hours. But its all part and part of fieldwork, those little tests, trials and tribulations. 

Every day is an adventure!

Buenos noches de Tenerife!

Day 17 - Volcan de Teneguia and Llano del Banco flows (at last!)

Today was a great day. I was responsible for the soil gas sampling and our main area to sample was on and around the volcano responsible for the 1971 eruption, Teneguia.

The first image Doesn't show Teneguia from her best angle but it does show the clear contrast between the colour of the young lavas of Teneguia (and some of San Antonio) and Roque Teneguia.

It's more a moonscape but with Blue skies. Teneguia has three craters and covers the field of view with the contrasting pale Roque Teneguia to the far right.

Roque Teneguia is much older than the surrounding landscape at ~56,000 years. This pale colour is due to the lava responsible for forming this rock having a much greater evolved composition. This outcrop is what remains of a phonolite dome, now devitrified and spherulitic due to chemical weathering.

This site is of importance for other reasons also. It is only one of two sites, not just within the Fuencaliente municipality, but the island as a whole, where the plant species centaurea (Cheirolophus junoianus) is found. Evidence suggesting this area may have been a sacred place for the pre-Hispanic population of the island is presented in funeral remains and rock carvings. This area would have appeared very different during these times.  

The two main highlights of today were sampling/climbing to the top of Volcan de Teneguia and walking around the Llano del Banco lava flows. 

Volcan de Teneguia, 1971 eruption, second active crater

Teneguia has 3 craters, all of which contributed to the 1971 eruption. The eruption began with the smallest crater in the northwest of the volcanic field and progressively moved south with the second crater that in the above image and the third below. 

The first crater is towards the top of this image among the black lavas, taken from above the second crater, looking roughly north west. The reddy-brown colour in the foreground is due to oxidisation of  some of the individual minerals in the lavas at this location on the volcano

Crater three

Our final sample site on the volcano was the end of the crater rim in the upper right of this image. From this point looking inland, there is a great view of San Antonio volcanic cone.

San Antonio volcanic cone as seen from the rim of crater three of Teneguia

Soil gas sampling on the rim of Teneguia crater three

Making our way back to crater two for the climb back to the car, we found a great example of a small fossil fumarole. We took a small sample of the white rock back to the car with us and put a small amount of 10% dilute HCl on it. If it effervesces (fizzes) the rock, or at least the alteration minerals within the sample, contain CaCO3. This proved to be absent of CaCO3, meaning the white is likely to be associated with chemical weathering to clay containing magnesium - probably the smectite group. 

Fossil fumarole (hammer for scale) on the rim between crater two and three

The next highlight of the day involved finally having a walk around the Llano del Banco (1949) lava flow. As stated in an earlier post, the flow started high up on the western flank of Cumbre Vieja, just below Pico de Birigoyo, it flowed all the way to the sea just over 7 kilometers away, before effusion rates dropped, resulting in the formation of an ocean platform, adding more land to the west of the island. 

I have to admit, after seeing just a tiny snippet of these stunning flows on filming day, I was pretty desperate to find time to go back and explore just a little.

The flows combine blocky, a'a' and pahoehoe morphologies and there are channels, collapsed tubes, windows, tubes that become channel and channels that become tubes everywhere you look. In previous posts I have already presented images of pahoehoe lava from this flow, but below there are examples of some of the other features observed.

 This is probably a lava tube that has collapsed simple because the debris on the surface within the channel is broken up, but not in the style of block/a'a' morphology, with pahoehoe below the debris

 The sunlight made photographing some of the features a challenge. In the centre of the image is a window. These are often seen in Hawaii. They are small areas of a lava tube where the roof is yet to form. It is possible to look through (carefully) and watch molten lava move beneath

This is one of many examples observed of a lava tube transitioning to a channel

 In some areas the lava has formed small topographic highs that we were soon to discover indicated the location of lava tubes larger than previously seen.

Walking to the end of the constructed walk way, Hannah got to a point before me and excitedly called back to tell me to hurry up. We were looking down on a pretty big opening - a lava tube.

A large lava tube, the photo doesn't really do it justice

We walked down in to the lava tube following the constructed route where it became apparent that this was in fact an area where the lava tube started as a channel and a tube roof had started to develop, but due to a drop in effusion rate had never completely formed. This appears to have happened at least three times during the eruption phase, with the final drop in effusion remaining consistent for a long enough period to form a tunnel roof. 

The lava tube was thiisssss biiggggggg......

We were not expecting this!

Every day is an adventure!

Buenos noches de La Palma!

Day 16 - Filling in the gaps

Day 16 was a business as usual day. I was on CO2 efflux and soil temperatures today. A lot of today's sampling involved filling in gaps - areas that we had for various reasons been unable to sample on our first visit to the location in question.

We returned to the Llano del Banco lava field where we both were filmed earlier on in the internship. We collected some soil gas samples and had the opportunity to take pictures if the source location of the lava flow high in the hills - wishing just a little that we could actually go and see the locality. 

  Source of the Llano del Banco lava flow up in the hills to the right of the image - taken from the lower part of the flow. 

There were also some great examples of pahoehoe flow at this locality.

Pahoehoe of the Llano del Banco flow, San Juan eruption, 1949

Today's sampling also took us high in to the hills, sampling on the flow of the El Charco eruption of 1712.

El Charco lava field, taken just below the crater looking west

We also spent sometime today, and on other days, sampling among the banana plantations, where there is often a strong smell of sulphur, though this is not related to any volcanic activity but rather dilute sulphur is used to feed the banana plants (as well as the grapes for the wine)

Bananas!

And among the pine forests that three years ago were damaged by a forest fire, but are recovering well.

Fire damaged pine forest

Every day is an adventure!

Buenos noches de La Palma!

Day 15 - Pilot Whales. In the wild. Where they belong!

As Paulo left last night for the 4am ferry this morning and Samara had driven him to the port and returned at almost 5am, we took they day off so she could snooze and do some work on her final PhD presentation.

We decided to treat ourselves to a boat trip, that had a high success rate of seeing whales and dolphins (though never guaranteed). We went out on the Inia Ocean Explorer, a purpose built R. I. B. (Rigid Inflatable Boat) it emits little noise as it is equipped with low-noise and low-vibration motors. The company adheres to the directives of gentle whale watching by keeping a minimum of 60 meters away from any sighted animals and engines off to drift should they approach us, which often happens with the dolphins as they are familiar with the boats and enjoy playing in the waves.

The Inia is the small yellow boat (12 seats)

My life is a little complete, as we got to see a family pod of pilot whales with young. In the wild. Where they belong! We also saw a small pod of Atlantic Spotted Dolphins, but these guys were too fast to get any good pictures of.

Pilot Whales

After seeing the whales and dolphins we headed out approximately 4 miles at a speed of ~21 knots (~45 mph land speed), jumping the waves and bouncing around, which was great fun!

We then headed back in towards land at a slower speed. We were taken past a small village that had been built on a wave cut lava platform at the very base of the cliffs, a location used during the summer months by locals. Further along we were taken in to a sea cave, the entrance to which was surrounded by columnar joints.

The geology of the cliffs was quite interesting with networks of high dykes and deposits of pyroclastics cut by lava channels (I shall add pictures when I have rectified a technical issue with my camera).

We headed back to the port passing the Taburiente caldera opening on the way.

After disembarking, we headed for a tapas lunch, then relaxed on the beach for a while before getting the bus back to Los Canarios.

Every day is an adventure!

Buenos noches de La Palma!

Day 14 - San Antonio volcano

Today is Paulo's last day with us before heading home to Cape Verde.

Though today is a day of sampling, business as usual, there is a feature we sampled around that is worth discussing a little, so here I go!

Along with the most southerly volcanic centre of Teneguia, responsible for the 1971 eruption, there is a much larger volcanic cone immediately above Teneguia that was responsible for the 1677 eruption. Together these two volcanic centres are responsible for extending the land mass of the island of La Palma in a southerly direction.

San Antonio crater taken from the western crater rim

The eruption of San Antonio was a Strombolian style eruption that resulted in minimal destruction to the area. However, the lava flows were responsible for burying Fuente Santa, the hot spring that is the namesake of the municipality of Fuencaliente. 

Fuente Santa, or Holy Fountain, was a hot spring whose waters were believed to hold healing properties by European travellers and the ancient inhabitants of the island alike. The waters were even shipped to South America, bringing some wealth to the area. Its powers were so amazing to the people that it was also referred to as Fuente Caliente - Holy Source. 

In writings by Nicholas Sotomayor "On November 13, 1677, a quarter of an hour before sunrise, the Earth shook and the underworld opened at the foot of the Mount of Los Corrales. Several lava flows were diverted away from the hot springs, but on November 23, a large flow moved towards the spring and no more could be done to stop the inevitable. This lava flow was coupled with the collapse of part of the cliff where the source of the hot spring was located. Despair among the people of the area raged as the spring was buried and the land was extended to the sea by 400 meters. 

Fuente Santa (image from canariesactual.com)

Recently, the Ministry of Public Works of the canary Islands Government in collaboration with the City of Fuencaliente has discovered the location of the springs and established access. Analysis of the waters reveals high salt an CO2, as well as water temperatures of 60 degrees Celsius. It is hoped that in the near future, these waters will once again be used in a spa that will bring additional wealth back to the region. 

Down near the coast, among the lava flows of this eruption, where roads now cut the flows, it is possible to observed some good examples of lava flows in cross section that demonstrate the rubbly top and base and a solid core with vesicles elongated with the flow direction. 

Cross section through a lava flow

The rubbly at the top and base of the lava flow is due to these surface coming in to contact with the cooler underlying deposit and the atmosphere. The outer edges of the flow begin to cool but the core of the flow continues to move. The friction generated between the still flowing lava and the cooled and partially crystalized outer edges causes the outer edges to break up in to small blocks, resulting in the rubble. 

Every day is an adventure!

Buenos noches de La Palma!

Day 12 & 13 - The Day the Cameras Came

Well day 12 was a business as usual day with me on the efflux and soil temperatures and Hannah working the soil gases. In addition to the work at hand, the features we saw today include a small ocean platform and the source of that ocean platform which was El Bucaro eruption centre, vents and fissures.

 Small ocean platform formed by the cooled lavas from El Bucaro that spilled in to the sea.

El Bucaro eruption centre.

However before the day's work on day 13, we had some extra work to complete. Today was the day the cameras came; Aaron Ramirez from Tandem Visual. We first made our way to the nearby Teneguia volcano, but on arrival it was quickly established that it was too windy for the microphones and for good sampling. So off we went on the hunt for another location - Samara had a good idea where to head too. I had a short interview on the Llano del Banco lava flows that are part of the much larger San Juan eruption. These flows are stunning and I will visit these in more detail another day. 

Mid- interview

Hannah was filmed on the same flows, in a slightly different location, I of course went on the hunt for some features and found a lava tube big enough to use myself as scale!

Lava tube big enough for me. 

The interview was followed by a slight change in location and a demonstration of the various techniques we were using in the field. As I was on soil gas sampling duties today, it is that that I demonstrated, by talking over the steps for the film as well as photos.

Demonstrating that I have been taught well!

The below link is to the short film. Made to help promote the GeoTenerife internships to future students. 

https://www.youtube.com/watch?v=Gy9l0nL7KG0

Once we had finished our filming it was back to business as usual. Today we finally got the chance to see the cloud 'waterfall'. The westerly trade winds bring the clouds in off the Atlantic. The cloud 'waterfall' flows over Cumbre Nueva in the middle of the island because it is at a slightly lower elevation than the Taburiente caldera rim to its north and Cumbre Vieja to its south. The clouds follow the topography of Cumbre Nueva and descend in to the valley.

 Cloud 'waterfall' tumbling over Cumbre Nueva

The day continued as per normal. On our lunch stop high up in the pine forests I went for a short wander while everyone else finished their lunch and found a small lava tube. Though small in diameter it is a perfect example of a lava tube.

Small lava tube

This lava tube is a great example of a tube that has been filled completely at some point during it's life time. The evidence for this is presented in the beautiful drips on the roof. These are drips of lava that would have formed as effusion rate dropped and the tube began to empty. The remains of a pahoehoe flow can be seen at the opening of the tube (bottom of image) and filling of the tube can just be seen towards the back of the tube. I was quite pleased with this little find!

It is time to chill and I will post again in the next day or so.

Every day is an adventure!

Buenas noches de La Palma!

Day 10 & 11 - Taburiente Caldera

After our trek on day 9, yesterday was a well deserved day off, involving a little wander around the island's capital of Santa Cruz a seafood lunch with a view and a bit of beach lounging on black sand.

Well you can't work and be serious all of the time!

 Lunch with this view!

Beach of black sand. The black sand is a combination of eroded lavas that surround the area and cover the island and volcanic ash. It sparkles in the sun like millions of tiny diamonds. 

Today we are off to sample Dos Aguas spring in the centre of Taburiente caldera. The caldera forms part of the north of the island, it is approximately 10km in diameter and the walls tower up to 2000m above the caldera floor. The highest point of the caldera wall is the Roque de Los Muchachos at 2426m asl. During the 15th century Spanish conquest of the Canary Islands, the caldera was the site of the last stand of the indigenous people of the islands, the Guanches. The Spaniards found the caldera impregnable and only defeated the Guanches people by coaxing their leader out of the caldera with the promise of talks. 

Although this is not an area where hazard monitoring is completed in depth, the spring is sampled twice a year, just as a precaution. Should any samples reveal any anomalous data, then further sampling of soil gases, efflux and temperatures would be collected.

Though called a caldera, this is not a caldera that has formed by the collapse of a volcanic summit due to pressure changes caused by the rapid emptying of a magma chamber. Instead this caldera formed due to deep erosion of the original summit volcanic crater.

Two images from separate points inside the caldera. 

The walk to the sample site is about 4km each way, most of which can be done along the currently dried up river bed of the Barranco de las Angustias. This is a treat because the deep incision caused by years of extreme erosion has exposed the upper part of the Seamount Series. Thus allowing for the observations of some fabulous spilite pillow lavas.

Spilite rimmed pillow lavas (Paulo's foot is at the left of the image (scale). 

Spilite is a term used to describe a basalt that has been hydrothermally altered by means of interaction with seawater. Spilite rims are often formed on pillow lavas as the glass rind undergoes extensive alteration to chlorite. Such interactions between hydrothermal fluids of seawater origin with basalt often results in greenschist facies mineral assemblages of albite, chlorite, sphene, actinolite and epidote. 

Also seen forming the walls of the caldera are endless and sometimes complex networks of sills, dykes and sheeted dykes (though not seafloor spreading) with compositions varying from peridotite, pyroxenite, anorthosite, gabbro and syeno-gabbro.

 Sills and dykes providing evidence of at least four different intrusive events

'Sheeted dykes' (Paulo for scale), they are sheeted in the sense that a dyke has been split by a second dyke, then a third and so on. This is evident by the presence of chilled margins along one side of the dyke only. 

Samara did the sampling at the spring while I observed. This was for two main reasons; I have never sampled from a water source of any kind before and this was the only site this would happen at, so it had to be right. 

On locating the spring and starting to record data, the first things to be recorded were the ambient and spring temperatures. Multiple samples were collected from the spring to analyse the fluids for values of dissolved gases such as Helium ratios, Hydrogen and Carbon Dioxide, Calcium Carbonate, cations of calcium, magnesium and potassium and anions, as well as completing in situ testing for pH and conductivity. Three methods will be used for analysis of the fluids; micro-chromatography, quadrupole mass spectroscopy and isotope ratio mass spectroscopy. 

After finishing our sampling we walked further in to the caldera to find the Cascada des Colores - The Waterfall of Colours.

Cascada des Colores

You definitely need to know where to go as it is tucked away up stream, that involves a little wading and rock hopping to get to it. Just a trickle now, you wouldn't want to be in here if it rained!

It's a very pretty waterfall, the colours of the rocks are due to oxidation of iron at different concentrations and over time. Oddly the water itself runs clear from the falls but turns the reddy-brown of iron within a few meters of the falls. It is also only water that follows this specific route from the base of the falls to where the stream disappears underground 2km to the southwest, that turns this colour. The water above the falls and the water from other falls in the caldera also run clear.

Orange stained water due to iron concentrations only occurs along one water route within the caldera

Every day is an adventure!

Buenas Noches de La Palma!

Day 9 - Ruta de Los Volcanes

Pointing the way!

Today was a toughie I must say, but so much fun!

Most days we aim to sample approximately 50 sites in order to meet the three week deadline of completing 568 sample sites. But today was only 23. Why? I hear you ask, well here is why.

Today was a 5am start. Up ready and out before the sun, An approximately 30 minute drive to where the 4 x 4 will be left for the day; just east of El Paso, up in the hills by the loggers tracks, about 800m above sea level.

The Ruta del Los Los Volcanes runs across the crest of Cumbre Vieja ridge and is truly magical, walking above the so called 'sea of clouds', there is a wide range of geological and volcanic features. It's a one-of-a-kind landscape with the dizzying depths of Hoyo Negro, the lapilli fields of Montañas de Feugo, lava tubes and the warm grounds of Teneguía. This ridge is the site of over half the volcanic activity in the Canary Islands during the last 500 years.

It is 7.30am. Here begins the hike and days sampling. We start by checking we have all the necessary equipment and off we go. We gradually climb to the top of the most northerly and highest point of Cumbre Vieja; Pico de Birigoyo which sits at an elevation of 1945m above sea level.

Samara, Paulo and Hannah starting part of the ascent - 1200masl, 750m to go!

During the ascent it was possible to see across to Tenerife and Mount Teide rising above the clouds surrounding the island brought in on the trade winds. Further up and from the summit, it was also possible to see La Gomera and El Hiero.

A hazy Teide as seen from half way up Birogoyo

At the summit we stopped to take our first samples of the day, 2 soil gas samples, surface temperatures, ambient temperatures and CO₂ efflux data. The view from the top was pretty cool and very beautiful with the buildings in the town of El Paso just tiny little specs so far down. From here we could see the ocean on both sides of the island with ease.

At the summit of Pico de Birogoyo

Once ready, ensuring we had not left behind any equipment we set off walking south down in to a small valley that separates Birigoyo and the volcanic cone of Barquita.

We sample in the small valley and as we make our way around Barquita, then again as we descend slightly. The paths are far from even, straight or even of easy walking, but rather zigzags left and right, up and down and volcanic, well everything from weathered and crumbly lava to welded tuffs or unconsolidated deposits.

The day is beginning to get warm, with the added physical activity and the elevation to contend with leading to lower oxygen levels in the body, dehydration and ease of sun burn if you're not careful - so we all take our time. By about 10 am it was a quick stop to sample and a little refuel, then off again.

The first impressive sight of the day is Hoyo Negro eruption centre, one of the vents (in this case large vent) that forms Volcán Nambroque. The other two vents of this volcano are Duraznero and Llano del Banco, the volcano is better known as San Juan.

Hoyo Negro

It is known as San Juan because on 24th June 1949, Saint John's Day, the volcano came to life. The eruption began in the southern vent of Duraznero where a lava lake formed and over flowed down the eastern side of the Cumbre Vieja ridge.

Part of the Duraznero lava lake

A voluminous lava flow began at Llano del Banco on July 8th. The large volumes of lava flowed down the western flank all the way to the sea forming an extensive coastal platform. 

On July 12th the very deep vent of Hoyo Negro erupted, the violent eruptions thought to be the most explosive on the Canary Islands of historical times, were degassification eruptions of the system, no lava was emitted.

During this three phase eruption an earthquake occurred with its epicentre near Jedy. The result of this was fault propagation to the surface and a 2.5km long trace with maximum vertical displacement of 4m between Hoyo Negro and Duraznero. It has not been identified to the south of Duraznero and traverses down slope to the north of Hoyo Negro. These fault surface traces (the San Juan fault) are the first of their kind on the island and are the reason for the concerns regarding slope instability of the western flank of Cumbre Vieja. In 2000, the BBC broadcast a program in which suggestions were made that half of Cumbre Vieja could collapse in to the Atlantic Ocean. Several articles have been released in the last 15 years or so that have concentrated on modelling various aspects of the western flank of Cumbre Vieja. These models look at volcanic scenarios, collapse scenarios, fault networks, lengths of faults and tsunami modelling and all suggest any major collapse and resultant tsunami is highly unlikely.

Lava flows from this eruption flowed down both the east and the western flanks with the main flow on the west appearing at the surface to the north and flowing down to the sea.

This eruption was the first on the Canary Islands in the 20th century, there had been 13 years of earthquakes on and around La Palma in the run up to the eruption.

A small section of the fault trace. The offset towards the bottom of the image is about 50cm.

Continuing on with our sampling and volcano hiking, after climbing a steep path where the underfoot conditions were poor because of ash (sometimes felt like walking on the spot!) next we arrive at Montaña Negra. Walking along a narrow path, we stop to sample and we are above the clouds - I'm on top of the world!!!!!!

Above the clouds!

We are starting to descend from the ridge crest now, with just a few sample sites to go. We are walking through pine forests and ash fields that have been pockmarked by huge and beautifully shaped volcanic bombs

Teardrop shaped volcanic bomb - one of thousands!

Time to head home, we descend through the lapilli fields of Montaña de Fuego to the west of San Martin, making it to our meeting point where a member of the council of Fuencaliente comes to collect us. He drops us back to the accommodation, then takes Samara and Paulo back to collect the car while Hannah and I sort through the samples and data from the day's big adventure in the sky.

After a very long day, a 21km hike with field equipment in tow an early night was had by all and a much needed day off tomorrow is required by all.

Every day is an adventure!

Buenas noches de La Palma