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Earth of fire

Actualité volcanique, Articles de fond sur étude de volcan, tectonique, récits et photos de voyage

Articles avec #excursions et voyages catégorie

Publié le par Bernard Duyck
Publié dans : #Excursions et voyages

The stratovolcano Sete Citades and his circular caldera, 5,000 meters in diameter and a depth of 300-500 meters, occupy west of São Miguel. Its highest point, Pico da Cruz, is 856 meters, or 3,000 m above the basalt plateau forming the underbody of the Azorean archipelago.

The bottom of the caldera is occupied by two connected lakes, the Lagoa azul and the lagoa verde and post-caldera structures.

Legend tells that the two lakes, green and blue, were created by the tears of a princess and her lover, a shepherd, during their separation ... the color of the water recalling the color of their eyes.

 

São Miguel l / Azores - Aerial view of the caldera Sete Citades - photo Meteopt

São Miguel l / Azores - Aerial view of the caldera Sete Citades - photo Meteopt

São Miguel / Azores - the caldera Sete Citades and Lagoa Verde & Azul - photo U.Sverdrug

São Miguel / Azores - the caldera Sete Citades and Lagoa Verde & Azul - photo U.Sverdrug

The stratovolcano is formed by a stack of lava flows (ankaramite, basanite, alkali basalt, hawaiite, mugearite and tristanite) and pyroclastic fallout.

The oldest subaerial rocks include trachyte domes and tristanite, and flows exposed at the base of the wall of the caldera, and the coast to the west and south of the volcano. Flows of  trachyte, located at the base of the NO wall of the caldera, is dated to 210,000 years; another of tristanite, located on the west coast to Ponta da Ferraria, date of 74,000 years.

The stage, which gave the caldera its present size, is dated to 22,000 years, and follows the issuance of trachytic pumice.

São Miguel / Azores - Geological Map of stratovolcano Sete Citades - doc. in Geology of Three Late Quaternary Stratovolcanoes on Sao Miguel, Azores – by R.Moore

São Miguel / Azores - Geological Map of stratovolcano Sete Citades - doc. in Geology of Three Late Quaternary Stratovolcanoes on Sao Miguel, Azores – by R.Moore

At least twenty-two post-caldera eruptions have occurred, including six in his enclosure, with a high phreato-magmatic component; and 16 on the flanks of the volcano.

Eruptions in the caldera are relatively recent : six vents, whose eruptions formed cones and rings of pumice, occupy a position almost circular, following a likely concentric fracture
contemporary to the formation of the caldera.

From north to south and anticlockwise, are presented Seara Cerrado da Ladeira to the north, dated 3050 BC., The caldera do Alfreres, 2050 BC, the Caldeira Seca, dated 1444 (?), two domes of trachyte with their top occupied by a lake, lagoa Rasa, dated of the year 380, and the lagoa de Santiago, dated of the year 90. the cinder cone Cerrado das Freiras is built to the east of lagoa azul in 1444.

 

São Miguel / Azores - the caldera Sete Citades: Caldera Seca - Photo Christophe Finot

São Miguel / Azores - the caldera Sete Citades: Caldera Seca - Photo Christophe Finot

São Miguel / Azores - the caldera Sete Citades: the Lagoa Santiago - photo Time to go

São Miguel / Azores - the caldera Sete Citades: the Lagoa Santiago - photo Time to go

In 1713, an eruption of the western flank gave the Pico das Camarinhas and Ponta da Ferraria in 1110.

Since 1638, six submarine eruptions took place off the west coast, the last in 1880.

 São Miguel / Azores - Sete Citades: Pico das camarinhas - photo Geoparque Azores

São Miguel / Azores - Sete Citades: Pico das camarinhas - photo Geoparque Azores

São Miguel / Azores - Sete Citades : Ponta da Ferraria flows - photo Geoparque Azores

São Miguel / Azores - Sete Citades : Ponta da Ferraria flows - photo Geoparque Azores

Special landscapes and an eruption just after the arrival of the first Portuguese settlers gave the birth of various legends.

Of these, seven cities established in the caldera have been destroyed by the eruption that followed the arrival of the first Portuguese ... in conjunction with one of the possible positions of the mythical Atlantis.

It has in any case inspired the comic "The enigma of Atlantis", by Edgard P. Jacobs.

 

Album cover "L" enigma of Atlantis "and displays - Ed.Dargaud - a click to enlarge. Album cover "L" enigma of Atlantis "and displays - Ed.Dargaud - a click to enlarge.

Album cover "L" enigma of Atlantis "and displays - Ed.Dargaud - a click to enlarge.

About the comic  "The enigma of Atlantis" :

On holiday in the Azores, Professor Mortimer made ​​an astounding discovery. When exploring a chasm called "O foro do diabo" (the Devil's Hole), he found an unknown metal with amazing radioactive and luminescent properties. He think of Orichalcum, this mysterious metal that the Atlanteans, in Plato's, considered as valuable as gold. The discovery is important enough to warn that his friend, Captain Blake. The latter joins him in São Migue and events rush. Someone steals the specimen that Mortimer had left in his villa. Blake and he did that time to see a strange craft through space at the speed of light, disappearing into the night. Increasingly intrigued, the two men decided to redo an expedition to "Foro do diabo" to found new samples. They are accompanied by a guide, Pepe and his assistant in the guise, which hides the adventurer Olrik their mortal enemy. The latter was hired by a foreign power to recover the precious ore. The descent into the dangerous calderas begins. This dive into the bowels of the earth will cause them to live their most extraordinary adventure. Elucidating a centuries-old mystery, they will leave to the discovery of Atlantis, its people and its enemies, explore the lost continent and risk their lives to save the peace in the Atlantean Empire. They brave many dangers to return to our world where Atlantis remains an unsolved riddle ... The least of these dangers are not Olrik ...

 

Sources :

- Geology of Three Late Quaternary Stratovolcanoes on Sao Miguel, Azores – by R.Moore - link

- Global Volcanism Program - Sete Citades

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages

Furnas volcano located at the eastern tip of the island of Sao Miguel, contains two nested calderas, the youngest of 6 km. wide and an older, larger but less distinct in the local topography. The northeast wall of the former caldera notch the west wall of the caldera Povoação of the ancoent Nordeste volcano.

Sao Miguel - the nested calderas Furnas (dotted and dashed boundaries) -  in Geology of Three Late Quaternary Stratovolcanoes on Sao Miguel, Azores – by R.Moore

Sao Miguel - the nested calderas Furnas (dotted and dashed boundaries) - in Geology of Three Late Quaternary Stratovolcanoes on Sao Miguel, Azores – by R.Moore

Activity of Furnas volcano have started here about 100,000 years, with some 85 eruptions recorded; ancient rocks are "tristanites" exposed in the cliffs of Ribeira Quente and cover the flows of the Nordeste volcano.

There are about 30,000 years, a Plinian eruption and the issuance of trachytic ignimbrites are responsible for the formation of the oldest caldera; they will be gradually filled by various eruptions.

Latest Furnas caldera was formed 12,000 years ago, in response to the ejection of trachytic pumice (subaerial volume estimated 7 km ³, but more importantly including the impact in the ocean, impossible to quantified) which can be seen in deposits 10 km. north of the village of Furnas. This ignimbrite unit is called "ignimbrite Povoação." Three cones of tristanite, two of which related to the flows, 
are dated post-caldera . Similarly, a series of seven domes of trachyte, whose the Pico do Ferro, are located on fractures formed during the collapse of the caldera.
 

Sao Miguel - Furnas caldera, the Lagoa das Furnas

Sao Miguel - Furnas caldera, the Lagoa das Furnas

The post-caldera volcanic activity has been significant in the past 5000 years; at least 11 layers of trachytic pumice testify, classified " Furnas A to  Furnas J" and the Pico do Gaspar, a trachytic lava dome located to the East of the crater lake Lagoa das Furnas.

Its formation follows several Plinian eruptions accompanied by pyroclastic flows and the formation of two nestled rings of pumice;  they were dated respectively 840 + / - 100 and 1441 years latter, which occurred during the Little Ice Age, issued 100 million cubic meters of tephra; it is classified as VEI 4.

The last eruption of VEI 5, dated September 3 to November 2, 1630, resulted in hundreds of dead on the island; it is accompanied by significant emissions of pumice, pyroclastic flows and the formation of a trachytic lava dome, the Diego Preto / Mont Areia, in the center of a ring of pumice, the Cova da Burra.

Azores - São Miguel - Furnas volcano: the dome of the Pico do Gaspar is encircled by a line of trees (between the lake and the summit lava dome) which marks the edge of the ring of pumice. - Photo Rick Wunderman / Smithsonian institute.

Azores - São Miguel - Furnas volcano: the dome of the Pico do Gaspar is encircled by a line of trees (between the lake and the summit lava dome) which marks the edge of the ring of pumice. - Photo Rick Wunderman / Smithsonian institute.

Azores - Sao Miguel - Furnas volcano: boiling spring - photo Geoparque Azores

Azores - Sao Miguel - Furnas volcano: boiling spring - photo Geoparque Azores

A fumarole field with thirty hot springs (15 ° to 60 ° C), and some geysers, is in the village of Furnas, north of the lake.

Geothermal areas are exploited by people to cook their stew, the "Cozido", they do simmer several hours in pots, wrapped in rags, in holes of 60 cm deep.

Among the ingredients composing the "Cozido" include  : cabbage, potatoes, carrots, sweet potato, with as meat, chorizo​​, chicken, beef and black pudding ... invigorating!

 

Azores - Sao Miguel - Furnas volcano - geothermal area and cooking platform of "Cozido" - photo Geoparque Azores

Azores - Sao Miguel - Furnas volcano - geothermal area and cooking platform of "Cozido" - photo Geoparque Azores

Sources :

- Geology of Three Late Quaternary Stratovolcanoes on Sao Miguel, Azores – by R.Moore - link

- Global Volcanism Program - Furnas

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages

São Miguel has a varied structure: an old massive east of the island, the complex Povoação; three stratovolcanoes with caldera : Sete Cidades, Agua de Pau and Furnas. These volcanic mountains are interconnected by recent alignments of cinder cones and lava flows: the region of the Picos.

Three Quaternary stratovolcanoes with caldera are the result of large eruptions, mainly trachytic nature, pyroclastic flows and ash fall.

The oldest caldera is the outer caldera of Agua de Pau, in a central position, dated between 26,500 and 46,000 years. Then there is a progression from west to east, to newer structuresin the west, the caldera Sete Citades dated 22,000 years, then the inner caldera of Agua de Pau, dated 15,000 years, and finally, in the east, that of Furnas, dated 12,000 years.

 São Miguel and the location of its caldera (map VolcanoWorld / Oregonstate.)
 São Miguel and the location of its caldera (map VolcanoWorld / Oregonstate.)

São Miguel and the location of its caldera (map VolcanoWorld / Oregonstate.)

  São Miguel - the massive Agua de Pau - photo Hansueli Krapf

São Miguel - the massive Agua de Pau - photo Hansueli Krapf

The Agua de Pau, a central stratovolcano :

The oldest subaerial rocks
of Agua de Pau, dated of Pleistocene, include a dome of trachyte (181,000 years) on the south coast, a trachyte flow near the top (121,000 years) and trachytic tuffs (one unit 103.000 year old).

The main building consists of trachytic lava domes and pyroclastic deposits, dated between 100,000 and 40,000 years ago.
 

São Miguel, caldera Agua de Pau :  Lagoa do Fogo - photo Geoparque Azores

São Miguel, caldera Agua de Pau : Lagoa do Fogo - photo Geoparque Azores

São Miguel, the center of the island - The Agua de Pau central stratovolcano : the outer caldera, dotted / the inner caldera, bounded by stars - doc. in Three Late Quaternary Geology of stratovolcanoes on Sao Miguel, Azores - by R.Moore

São Miguel, the center of the island - The Agua de Pau central stratovolcano : the outer caldera, dotted / the inner caldera, bounded by stars - doc. in Three Late Quaternary Geology of stratovolcanoes on Sao Miguel, Azores - by R.Moore

The outer caldera, 4,000 of 7,000 meters, is dated from 26,500 to 46,000 years.
The inner caldera, 2500 to 3000 meters, was formed 15,000 years ago.

Activity post-caldera concerns
lava domes, which are set up on the northern and western flanks of the volcano and the caldera, where one of the largest eruptions in the Azores - VEI 5 - is dated 2990 BC ., characterized by the deposition of pumice of 3 km ³ (Fogo-A Plinian-fall deposit). The most recent caldera features a lake, Lagoa do Fogo. Cinder cones dot radial and concentric cracks.

The last trachytic explosive eruption took place in 1563, at the Cerro Qurimado vent on the side of the caldera NO. Hot springs, located on the side of NO., suggest the presence of magma or rocks
heated by it, associated with eruptions of the Pleistocene / Holocene near the surface.

São Miguel, caldera Agua de Pau :  Lagoa do Fogo, from Miradouro da Serra da Barrosa – photo Luis Silveira

São Miguel, caldera Agua de Pau : Lagoa do Fogo, from Miradouro da Serra da Barrosa – photo Luis Silveira

Sources :

- Geology of Three Late Quaternary Stratovolcanoes on Sao Miguel, Azores – by R.Moore - link

- Global Volcanism Program - Agua de Pau

- Geoparque Azores - Sao Miguel

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
Terceira / Azores - the massive of Santa Barbara - photo Geoparque Azores.

Terceira / Azores - the massive of Santa Barbara - photo Geoparque Azores.

 Terceira / Azores - Caldera Santa Barbara - photo Geoparque Azores

Terceira / Azores - Caldera Santa Barbara - photo Geoparque Azores

The west of Terceira home to the stratovolcano Santa Barbara. The massive of Santa Barbara, which occupies almost the entire terrain of western third of the island requires the shoreline look like a nearly perfect semicircle.

The volcano is truncated by a caldera complex on 1,900 of 2,700 meters, almost filled by seven trachytic domes.

On their sides, domes and domes-flows of trachytic lava, sometimes with obsidian, as Misterios Negros, one of the eruptive centers of the eruption of April 1761, or on the west side, the thick streams of Ponta do Raminho and Ponta do Queimado, near the lighthouse Serrata.

Santa Barbara, after a quick episode of lilited summit collapse, maintained, if not increased its overall volume by the contribution of domes and flows of trachyte.

Terceira / Azores - Santa Barbara Natural Reserve - photo Parques Naturais

Terceira / Azores - Santa Barbara Natural Reserve - photo Parques Naturais

Terceira / Azores - Thick trachytic flows west side of Santa Barbara - photos Geoparque Azores
Terceira / Azores - Thick trachytic flows west side of Santa Barbara - photos Geoparque Azores

Terceira / Azores - Thick trachytic flows west side of Santa Barbara - photos Geoparque Azores

Terceira / Azores - Volcano Misterios Negros - photo João Carlos Nunes - Governo dos Açores

Terceira / Azores - Volcano Misterios Negros - photo João Carlos Nunes - Governo dos Açores

The eruption of the oceanic volcano Serrata :

The submarine eruption off Terceira, in 1998-2000, was analyzed by the EVS - European Volcanological Society.
On 18 December 1998, Terceira's fishermen alert the authorities : a "column of white smoke" come out of the ocean at 9 km. NW. of the lighthouse of Serreta. The emission point, located at a depth of 500 meters, is close to the bench of Serreta, where an underwater eruption occurred in 1867.

To the left, location of floating blocks and bubbles marking the eruption Serrata, off Terceira (cross: January 1999 - triangles: February 1999 - rectangle: March 1999 - location of eruptions in 1867:Black circles) Courtesy of the Center of Volcanology of the Azores University (CVUA). - To the right, "lava balloons" from the dorsal Serreta - courtesy of CVUA - 1999 To the left, location of floating blocks and bubbles marking the eruption Serrata, off Terceira (cross: January 1999 - triangles: February 1999 - rectangle: March 1999 - location of eruptions in 1867:Black circles) Courtesy of the Center of Volcanology of the Azores University (CVUA). - To the right, "lava balloons" from the dorsal Serreta - courtesy of CVUA - 1999

To the left, location of floating blocks and bubbles marking the eruption Serrata, off Terceira (cross: January 1999 - triangles: February 1999 - rectangle: March 1999 - location of eruptions in 1867:Black circles) Courtesy of the Center of Volcanology of the Azores University (CVUA). - To the right, "lava balloons" from the dorsal Serreta - courtesy of CVUA - 1999

Terceira / Azores - The "lava balloons" from the dorsal Serreta float to the surface and produce white steam - courtesy of CVUA - 1999.

Terceira / Azores - The "lava balloons" from the dorsal Serreta float to the surface and produce white steam - courtesy of CVUA - 1999.

This volcano, called oceanic volcano Serreta was active until March 2000, along faults oriented NE-SW. and NW-SE., affecting an area of ​​several square kilometers.

Volcanic activity was intermittent, alternating periods of quiet little bubble emission and other characterized by blocks of basalt pillow smoking, and marked by a "migration of the vents."

Persistent emission of lava pillow floating and vesicular - lava balloons - sometimes filled with fluid lava and exploding in arriving in surface, before sinking after a few minutes is an unusual event ! (revised since then in the Canary Islands during the underwater eruption south of El Hierro, and called
"Restingolitas" )

This eruption involved a gas-rich basaltic magma; chemical analyzes made ​​by the Nordic Volcanological Institute confirm that they are alkaline basalts, od basaltic composition defined in the Azores.

Petrography reveals phenocrysts of pyroxene, olivine and feldspar in a glassy mass containing microliths including oxides.

The eruption was defined as serretyan type, a type preceding the surtseyan eruptions or "
Capelinos kind".

 

Sources :

- Geoparque Açores - Terceira

- Global Volcanism Program - Terceira

- SVE - société volcanologique Européenne - Ocanic volcano Serrata

 

 

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages

Located at 27 º 12 'west longitude and 38 º 40' north latitude, and vaguely elliptical Terceira has an area of ​​381.96 km ²; maxima its dimensions are 29 km long 17.5 km wide.

A low-relief plateau dominates the eastern part of the island. The central area is characterized by low and large crater of Caldeira Guilherme Moniz and all elevations of the Serra do Labaçal, which has its highest peak Pico Alto (808 m). To the west, takes place on the vast crater of the Serra de Santa Bárbara, where the highest peak of the island (1,021 m) mountain system.

 

Terceira / Azores - the port and the city of Angra do Heroismo, dominated by the cone of Monte Brasil - photo travelpost.noble-caledonia.co.uk

Terceira / Azores - the port and the city of Angra do Heroismo, dominated by the cone of Monte Brasil - photo travelpost.noble-caledonia.co.uk

Terceira is a massive island formed by three close calderas: the caldera and the massif of the Serra do Cume, Guilherme Moniz caldera and the mountains of the Serra do Moriao and the caldera and the massive Santa Barbara.

Santa Barbara, the latter, the younger, included a complex caldera filled with trachytic lava domes. On the outer slopes, these domes have the appearance of large masses extended by flows channeled into spectacular lifted.

The presence of a graben in the northeast of Terceira, which amended the slopes of a large stratovolcano, belongs to the WNW-ESE tectonic features of the Mid-Atlantic Ridge at the latitude of the Azores. The evolution of the archipelago will go through an analysis of the geomorphology diving.

 

Terceira / Azores - map of the various volcanic massifs and trachytic flows west and north - doc. Instituto Geografico

Terceira / Azores - map of the various volcanic massifs and trachytic flows west and north - doc. Instituto Geografico

The center of Terceira

Guilherme Moniz caldera forms a depression 4,300 meters on 2,300 m, dated 23,000 years, which is filled with pyroclastic and recent lava flows, such as those issued by the cinder cone Algar do Carvão.

This cone, 629 meters high, has the distinction of having the chemney of its crater remained open to a depth of 80 meters, hole in the bottom of which a lake of 400 sqm built. It can be accessed through the arrangements made ​​by cavers of Terceira: an artificial lateral tunnel avoids the vertical well, and gives access to a room where the ceiling is composed of andesitic rocks. Infiltration waters crossed the dross of the outer cone by undertaking elements and form white stalactites fifty cm., and spread and massive stalagmites of amorphous silicic kind.

Terceira / Azores - chemney of thecinder cone Algar do Carvão and its lake - photo Geoparque Azores.

Terceira / Azores - chemney of thecinder cone Algar do Carvão and its lake - photo Geoparque Azores.

Terceira / Azores - Siliceous Stalactites of the cinder cone Algar do Carvão - photo PatriciaR

Terceira / Azores - Siliceous Stalactites of the cinder cone Algar do Carvão - photo PatriciaR

 Terceira / Azores - Cross sectionof the  cinder cone Algar do Carvão Terceira / Azores - Cross sectionof the  cinder cone Algar do Carvão

Terceira / Azores - Cross sectionof the cinder cone Algar do Carvão

Southwest of the volcanic complex of north-central, we see a set of domes-flows and Strombolian cones, one of them has at its top a depression 100 meters in diameter, called Furnas do Enxofre: fifteen mouths emit hot sulphurous vapor that keep rocks at 80-100 ° C. Various vents, sulfur was deposited on needles 1 to 5 cm in length. These are the only witnesses of the latent present volcanism on Terceira.

 

Terceira / Azores - Furnas do Enxofre - photo José Luis Ávila Silveira / Pedro Noronha e Costa

Terceira / Azores - Furnas do Enxofre - photo José Luis Ávila Silveira / Pedro Noronha e Costa

 Terceira / Azores - Furnas do Enxofre - photo Geoparque Azores

Terceira / Azores - Furnas do Enxofre - photo Geoparque Azores

Pico Alto is a polygenetic volcano with a young caldera, almost completely filled by domes and flows, including Biscoito Rachado and Biscoito da Ferraria. A new high temperature geothermal area, measured between 200 and 230 ° C; was discovered in the area in 2004 following an exploration program and drilling by GeoTerceira.
 

Terceira / Azores - Domes and geothermal installation in the caldera of Pico Alto - photo Geoparque Azores

Terceira / Azores - Domes and geothermal installation in the caldera of Pico Alto - photo Geoparque Azores

South, Monte Brasil is a good example of a peninsular cone. This Surtseyan tuff cone  result of a basaltic underwater eruption ; with its largest diameter of 1.500 m and height of 205 m the highest point, there is an element of Angra do Heroismo site, which established its port behind this natural shelter. An isthmus, corresponding to an old cast down from the center of Terceira, then covered with different levels of projection, connects it to the island.

Silveira Bay, west of Monte Brasil, lets observe a succession linked to its history; down, the andesitic complex massif of the Serra da Ribeirinha and trachytes of the side of the Serra do Moriao followed basalts forming the core of the peninsula joining the Monte Brasil to the body of Terceira (visible under the castle 17th century). Thick ash levels trachytic, yellow color come after, covered with dark gray basalt tuffs of Monte Brasil, which include ankaramites, torn from deep bedrock of the island.

 

Terceira / Azores - Monte Brasil - photo audioanalogicodeportugal.

Terceira / Azores - Monte Brasil - photo audioanalogicodeportugal.

Near Angra, Pico do Gaspar is a Strombolian cone, resulting from a secondary eruption of the Serra de Santa Barbara, dated in the year 1200. His form in "nest" and the steeply inclined slopes are characteristic of a basaltic scoria cone consolidated.
 

Terceira / Azores - Pico do Gaspar

Terceira / Azores - Pico do Gaspar

Tomorrow, the west of the island and the last eruption.

 

Sources:

- Geoparque Açores - Terceira - link

- Onservations géomorphologiques à l'île volcanique de Terceira - par Gérard Mottet - link

- Global Volcanism Program - Terceira

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
Pico / Azores - Gruta das Torres - photo by Ana Janeiro / SAMI.arquitectos.

Pico / Azores - Gruta das Torres - photo by Ana Janeiro / SAMI.arquitectos.

The island of Pico, the second largest in the archipelago of the Azores, one of the most recent - 300,000 years old - houses, due to the composition of its lava flows, the largest number of lava tubes, about 80.

Gruta das Torres form a group of interconnected tunnels of lava. It is located in the pahoehoe and aa lava flows, issued from the parasite cone Cabeço Bravo, at various times between 500 and 1500 years ago. Wide of 50 cm to 22 meters, high from 1.1 m to 15 m, they have been explored scientifically only in 1990. With an estimated 5,200 meters (about 3,300 m and explored), it is the most large lava tube known in the Azores.

Pico / Azores - Stalactites in the lava tube of Gruta das Torres - photo Mike Norton

Pico / Azores - Stalactites in the lava tube of Gruta das Torres - photo Mike Norton

Pico / Azores - Lava tube of  Gruta das Torres - photo Mike Norton

Pico / Azores - Lava tube of Gruta das Torres - photo Mike Norton

These tunnels are a formidable drainage system of lava, as shown by the presence of more than seven levels on the walls, with benches and ledges, "lavacicles" (a generic term for stalactites and stalagmites in a lava tube).

 Pico / Azores - Gruta das Torres, carved by lava - photo Geoparque Azores

Pico / Azores - Gruta das Torres, carved by lava - photo Geoparque Azores

Gruta das Torres has two inputs, the first in a skylight, the other is protected by a building which houses the Visitor center, in harmony with the volcanic environment.

 Gruta das Torres - the Visitor Center - photo by Ana Janeiro SAMI.arquitectos.

Gruta das Torres - the Visitor Center - photo by Ana Janeiro SAMI.arquitectos.

Gruta das Torres - the Visitor Center, the perforated wall outside - photo by Ana Janeiro SAMI.arquitectos.

Gruta das Torres - the Visitor Center, the perforated wall outside - photo by Ana Janeiro SAMI.arquitectos.

Gruta das Torres - the Visitor Center, the perforated wall inside - photo by Ana Janeiro SAMI.arquitectos.

Gruta das Torres - the Visitor Center, the perforated wall inside - photo by Ana Janeiro SAMI.arquitectos.

A perforated stone wall, a "volcanic lace" is at the junction of the building and the lava tunnel itself ... filtered light streaming naturally to illuminate the interior. The rest of the building is lined with an impermeable black finish in harmony with the color and texture of the vitrified lava in the tube.

Gruta das Torres - the furnished lava tunnel portion - photo by Ana Janeiro SAMI.arquitectos

Gruta das Torres - the furnished lava tunnel portion - photo by Ana Janeiro SAMI.arquitectos

Gruta das Torres was chosen with 17 other lava tubes in Pico, for inclusion in a set of 30 tubes proposed for inclusion in the list of Unesco World heritage.

 

Sources :

- Geoparque Açores - Pico - Gruta das Torres - link

- Caves and pits from the Azores, with some comments on their geological origin; distribution and fauna - by P.A.V.Borges & al.

- Archdaily - Gruta das Torres Visitor Centre / SAMI-architectos - link

- ENS Lyon - l'intérieur des tunnels de lave - Açores : Gruta das Torres

- Amigo dos Açores - Volcanic caves

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages

Pico Island, immediately adjacent to Santa Maria which it is separated only by a shallow sea arm, is dominated by the volcano of the same name. Its area is 445 km ² and is 42 km by 15.2. Discovered before 1439, it was first called all São Dinis, before being colonized from 1460.
 

Pico / Azores - the Montanha do Pico - photo Geoparque Azores.

Pico / Azores - the Montanha do Pico - photo Geoparque Azores.

The Montanha do Pico, or Ponta do Pico, is a stratovolcano which rises to 2,351 meters above sea level. The dominant basaltic volcano was built on the volcanic complex Montanha, a former elongated volcano slopes more sweet, consisting of basaltic lava flows and adventitious cones.

He wears a summit crater 500 meters wide and 30 meters deep, in which there is a small cone with steep walls 70 meters high: Pico Pequeño or Piquinho, one of the few peaks of the Azores to be covered with snow in winter.

The top of the Piquinho present a permanent degassing consisting of water vapor at a temperature between 50 and 75 ° C (depending on the boiling temperature settings  function of altitude and barometric pressure)

 

Pico / Azores - the top of the Montanha do Pico, with the Pico Piquinho and snowy high slopes

Pico / Azores - the top of the Montanha do Pico, with the Pico Piquinho and snowy high slopes

Pico / Azores - the Montanha do Pico - the summit crater - photo Unukorno

Pico / Azores - the Montanha do Pico - the summit crater - photo Unukorno

Pico / Azores - the Montanha do Pico - Pico Piquinho - photo Unukorno

Pico / Azores - the Montanha do Pico - Pico Piquinho - photo Unukorno

Historical eruptions are located on the slopes of Pico and in the east rift zone dotted with pyroclastic cones Hawaiian / Strombolian type:  the Sao Roque Piedade volcanic complex.

In 1562-64, the rift area southeast produced lava flows that reached the north coast; near vent is responsible for a lava flow joining the sea on the south coast. The flank eruption of 1718 fueled flows that reached the both coasts.

The last eruption, located on the SE flank at 400 meters, is dated 1720.

Left, Pico - the lava flows of historical eruptions - doc Padang & al - right, the relief of the island, with Montanha do Pico and cones dotting the East Rift Zone - doc. Governo Regional dos Açores - a click to enlargeLeft, Pico - the lava flows of historical eruptions - doc Padang & al - right, the relief of the island, with Montanha do Pico and cones dotting the East Rift Zone - doc. Governo Regional dos Açores - a click to enlarge

Left, Pico - the lava flows of historical eruptions - doc Padang & al - right, the relief of the island, with Montanha do Pico and cones dotting the East Rift Zone - doc. Governo Regional dos Açores - a click to enlarge

To the west of Pico, in the channel of Faial, the Ilheus da Madalena, 52 and 59 meters high, are the remains of a volcanic underwater apparatus destroyed by wave erosion and tectonic forces. They consist of palagonitised tuff ,of phreatomagmatic origin.

 Pico / Azores - the Ilheus da Madalena - photo from Wikimedia commons

Pico / Azores - the Ilheus da Madalena - photo from Wikimedia commons

Seen from Pico, Ilheus da Madalena and in the background, the island of Faial - photo Carlos Luis MC da Cruz

Seen from Pico, Ilheus da Madalena and in the background, the island of Faial - photo Carlos Luis MC da Cruz

The vineyards of Pico and the Currais :

The vineyards of Pico form a landscape listed by UNESCO in 2004.

Vines are planted in a rich, dark volcanic soil in small plots surrounded by walls facts in lava rock (from mopping the soil at walls implantation). These walls, reaching the waist, called " Currais or Curraletas ", have a protective function against salt spray near the ocean, and recovery and storage of heat returned to the grapes during the night.

Grapes of exceptional quality produce excellent sweet wine, the Verdelho do Pico, "bronze and aristocratic."

"Basalto", "Lajido" and "Terras de Lava" are designations of Pico wines that refer to a human-nature relationship that the islanders are honored. The wine cooperative of Pico Island, to Areia Larga, focused the local production, which adopted new varieties, and can be visited.

Other local delicacies: eaux-de-vie of fig and loquat, honey of Pittosporum flowers, cheese soft dough of Pico.

 

Museu do Vinho do Pico, curraletas of vinha - photo José Luis Ávila Silveira / Pedro Noronha e Costa

Museu do Vinho do Pico, curraletas of vinha - photo José Luis Ávila Silveira / Pedro Noronha e Costa

Sources :

- Geoparque Açores - Pico - link

- Global Volcanism Program - Pico

- Siaram - Visitazores - le patrimoine - link

- Le Monde - "Aux Açores, sur les pentes du Pico - une île noire, enivrante" - link

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages

The island of Faial, an irregular pentagon of 21 km. x 14, is a well-known stage for sailors crossing the Atlantic and coming anchor and refuel in the port of Horta, the capital.

Peter's bar is the favorite benchmark of  thirsty crew.

Discovered in the first half of the 15th century, it was designated as Ilha da Ventura / Island adventure, before being called Ilha de São Luís / island of Saint Louis.

The current name Faial comes from the Portuguese "Faia", designating an abundant originally shrub, Myrica faya (Firetree).
It is nicknamed the "Blue Island", because of ubiquitous hydrangeas, boosted by an humid and temperate climate.

 

Hydrangeas of Faial - photo naturalland treakearth

Hydrangeas of Faial - photo naturalland treakearth

Map of the island of Faial and its various volcanoes

Map of the island of Faial and its various volcanoes

From a geological point of view, the island concentrates the different volcanic formations:

- A shield volcano, the volcano Riberinha in the extreme northeast, which is the origin of the proto-Faial Island. Since then, he has been largely destroyed by erosion and tectonic forces, causing the graben Pedro Miguel.

- A stratovolcano, with the volcano Caldera, with a central position.

This polygenic building has since 15,000 years, 14 subpliniennes eruptions, including two very violent, dating from the year 340 - 350 and from 800 -  810 AD,  at the origin of ignimbritic deposits exposed on the northern flank.

The current caldera, steep-walled, measuring 2,000 meters in diameter and 400 m deep. Classified as a nature reserve, the descent into the caldera is prohibited.

Its flat floor features small buildings, including Capelo, a diameter of 150 meters and a height of 30. It houses small temporary lakes.
 

Faial / Azores - the caldera of the volcano Caldera, and Capelo, a post-caldera cone (in the center of the photo) - Photo Geoparque Azores.

Faial / Azores - the caldera of the volcano Caldera, and Capelo, a post-caldera cone (in the center of the photo) - Photo Geoparque Azores.

 Faial / Azores - into the caldera - photo Geoparque Azores.

Faial / Azores - into the caldera - photo Geoparque Azores.

- Monogenetic volcanoes of basaltic origin, scattered on the Horta's platform and the Peninsula Capelo.

The Horta's platform houses the
Monte das Moças, the Monte Queimado et the Monte da Guia.

The latter, of submarine origin, consists of a Surtseyan tuff cone open to the sea by two twin craters; the cone is connected by an isthmus of dune to Monte Queimado.

 

Faial / Azores - Monte da Guia - the twin craters seen from the top of the tuff cone - photo Geoparque Azores.

Faial / Azores - Monte da Guia - the twin craters seen from the top of the tuff cone - photo Geoparque Azores.

 Faial / Azores - right, Monte da Guia - left, the harbor of Horta - photo océans-évasion

Faial / Azores - right, Monte da Guia - left, the harbor of Horta - photo océans-évasion

The peninsula do Capelo consists of a linear chain of basaltic volcanoes, the seat of major eruptions in historical times: the Cabeço do Fogo, in 1672-1673, and Cabeço dos Capelinhos in 1957-58.

We see it in detail later.

 

  Faial / Azores -  Peninsula do Capelo - photo Geoparque Azores

Faial / Azores - Peninsula do Capelo - photo Geoparque Azores

South-west of the island, the Morro do Castelo Branco is a trachyte dome, covered by pyroclastic deposits from the volcano Caldera.

His name, Branco / white, come from the light colored clay deposits present in the upper part. Strong marine erosion has left high cliffs.

Azores - Faial island - 1.

Sources :

- Geoparque Açores - Geossitios Faial - link

- AGU - American geophysical union : "Azores hotspot deep signature"
- ATA  - Association turismo Açores.

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages

While some cards mention its existence from the 14th century, it is considered that the Santa Maria island was discovered by Portuguese sailors in the 15th century and the first of the populated islands forming the archipelago of the Azores, to 1430-1450 .

Sometimes called "yellow island" because of wild yellow flowers that bloom there in the month of February, she also called "Island of the sun", because of its drier climate over much of the island, and weather conditions more favorable than its neighbors throughout the year ... but it is also characterized by many other colors !

Santa Maria / Azores - organs of Ribeira do Maloás - photo Verdeazores

Santa Maria / Azores - organs of Ribeira do Maloás - photo Verdeazores

Santa Maria / Azores - organs of Ribeira do Maloás - photo Verdeazores

Santa Maria / Azores - organs of Ribeira do Maloás - photo Verdeazores

In the bed of the Ribeira do Maloás, 220 meters from its source, a waterfall of 15-20 meters showcases the prismation of a basaltic lava flow from the complex Pico Alto.

The prisms, UHF dimensions, form, at the top and bottom of the fall, a polygonal pavement  type Giants Causway.

Santa Maria / Azores - organs of Ribeira do Maloás - at the bottom of the fall, a polygonal pavement of erosion - doc. Wikiloc.

Santa Maria / Azores - organs of Ribeira do Maloás - at the bottom of the fall, a polygonal pavement of erosion - doc. Wikiloc.

Santa Maria / Azores - organs of Ribeira do Maloás detail - photo Paulo Henrique Silva

Santa Maria / Azores - organs of Ribeira do Maloás detail - photo Paulo Henrique Silva

In the extreme south of Santa Maria, Pontado do Castelo, a rocky promontory overlooking the sea.

The stratigraphic sequence includes marine sedimentary rocks, some with fossils, and submarine and sunaerian volcanic rocks. You can also see the vein intrusions.
 

Santa Maria / Azores - Pontado do Castelo - photo Geoparque Azores

Santa Maria / Azores - Pontado do Castelo - photo Geoparque Azores

Poço da Pedreira is an old quarry, where old basaltic scoria were exploited.

Consolidation over time of pyroclastic and red color of slag earned him the name of Pico Vermelho / red peak.

 

Santa Maria / Azores - Poço de Pedreira - photo Geoparque Azores

Santa Maria / Azores - Poço de Pedreira - photo Geoparque Azores

To Pedreira do Campo, a underwater sequence, old of 5 million years, is exposed, composed of marine sedimentary rocks rich in fossils at the base, and covered by basaltic hyaloclastite and pillow lavas.

These places are included among the 57 spots of the Azores Geopark.


 

Santa Maria / Azores - Pedreira do Campo - Photo Geoparque Azores

Santa Maria / Azores - Pedreira do Campo - Photo Geoparque Azores

Sources:

- Geoparque Açores - geossitios - link

- Verde Azzore - Vulcanismo Santa Maria - link

- Os Açores, ilhas de geodiversidade: o contributo da ilha de Santa Maria - João Carlos Nunes & al.

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages

When the weather seems to settle in the north, for some reason I think of the Azores !

Geodiversity of the Azorean archipelago is the result of the installation of the geotectonic micro-plate that supports, at the point of the Azores triple junction between the North American, Eurasian and African plates.

This geological diversity comes in many forms: cinder cones, maars, pit crater, calderas, domes and trachytic lava, volcanic organs, fumeroliens fields, pahoehoe lava fields, called "lajidos", delta of lava, called lava "fajãs", lava tubes, pillow lavas, obsidian, dykes and necks ... all the qualifier vocabulary goes!

 

Geotectonic pattern of the Azores - doc.adapté Nunes et al. 2006

Geotectonic pattern of the Azores - doc.adapté Nunes et al. 2006

In this context, the most southerly island of the archipelago, Santa Maria, has a special place:
- It has indeed the oldest of the group of islands rocks.
- Many outcrops of sedimentary rocks, including limestone, conglomerates and sandstones, characterized by the presence of many fossils are another feature.
- It is also the only island where you can see large outcrops of pillow lavas, in addition to various volcanic structures, some of which are part of geosite classified Azores.

 

 The island of Santa Maria - two morphological entities and major bays

The island of Santa Maria - two morphological entities and major bays

 Santa Maria / Azores - Baía de São Lourenço - photo Siaram.azores.gov

Santa Maria / Azores - Baía de São Lourenço - photo Siaram.azores.gov

Tectonics of the micro-plate of the Azores:

The raised floor of the Azores plateau is interpreted as being the result of the interaction between a mantle plume (Azores hot spot) and the MAR / Mid Atlantic Ridge, which took place there 85 million years. This interaction has migrated northward along the axis fault following the movements of the African plate to the SSE in a direction roughly parallel to the axis of March

The formation of the plateau of Azores have started there 20 Ma, to finalize there 7 Ma.
The entire plateau, after the decrease in volcanic activity has been affected by the rifting of the Mid-Atlantic Ridge.

The case of Santa Maria:

The oldest island of the archipelago, with formations dated 8.12 Ma, is characterized by a basaltic substrate, deformed by a series of NW-SE oriented fractures.

The presence of limestone and fossil deposits associated with marine formations, show a surtseyan past activity, and periods of flooding before the final output above sea level.

The soils of the western region mainly consist of red clay, the result of an alteration of pyroclastic deposits in hot and humid climate of Paleocene, when the sea level was 100 meters lower than the current level.

Santa Maria / Azores - Barreiro da Faneca, also known as the "Red Desert" because of the color of the clay formed by pyroclastic. - Photo Carlos Luis MC da Cruz

Santa Maria / Azores - Barreiro da Faneca, also known as the "Red Desert" because of the color of the clay formed by pyroclastic. - Photo Carlos Luis MC da Cruz

Santa Maria / Azores - Pico Alto - photo Ruben JC Furtado

Santa Maria / Azores - Pico Alto - photo Ruben JC Furtado

 Facho-Pico Alto volcanic complex formation is characterized by intense volcanic activity and submarine eruptions beginning there 5 Ma, and pillow lavas extensive production.

We find these pillow lavas, at an altitude of 180 meters above present sea level; they are responsible for the expansion of the island to its current size. Return below the sea level has resulted in a period of subaerial volcanism between 5 and 3 Ma.

Two main areas of different morphology can be distinguished:
Dry clay plain occupies two-thirds west of Santa Maria. The impermeability of the soil makes the arid region.
The eastern third consists of eroded hills and mountains, interspersed with valleys, and covered up by a thick vegetation or pasture. Highlights are the Pico Alto, with 590 m, Cavacas with 491 m, and Caldeira, with 481 m. This region is more humid, with strong winds, precipitation and fog, promoting vegetation rich in endemic.

The coasts are lined with cliffs, the highest of which are 340 m, Rocha Alta. They are interspersed with bays and sandy beaches protected or guarded by rocky islets.

Santa Maria / Azores - The Aveiro cascata, on the coast south of Santa Maria, unveiled by its erosion different sets of pillow lavas -. Visitazores Photo

Santa Maria / Azores - The Aveiro cascata, on the coast south of Santa Maria, unveiled by its erosion different sets of pillow lavas -. Visitazores Photo

Santa Maria / Azores - The early port of Calhau da Roupa - photo Carlos Luis MC da Cruz

Santa Maria / Azores - The early port of Calhau da Roupa - photo Carlos Luis MC da Cruz

Tomorrow, the site of Ribeira do Maloás.

 

Sources :

- Os Açores, ilhas de geodiversidade : o contributo da ilha de Santa Maria - João Carlos Nunes & al.

- The marine fossils from Santa Maria island - Patrícia Madeira & al.

-  " Interaction between the Mid Atlantic ridge and the Azores hot spot during the last 85 Myr. Emplacement and rifting of the hot spot-derived plateaus " par P.Gente & al. - CNRS 2003 in G³ electronic journal of the earth science.

- AGU - American geophysical union : "Azores hotspot deep signature"
- ATA  - Association turismo Açores.

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