Friday, 26 June 2015

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

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