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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 Jarvis Island, close to the new seamount discovered in August 2014 / link, is part of the Line islands, also called equatorial Sporades, a chain of seamounts, atolls and volcanic islands extending over 4,800 km in the central Pacific basin and surrounded by seabed over 5,000 meters.
Only twelve underwater volcanoes reach the level of the sea to form low islands and atolls, now lined with narrow fringing reefs extending only 1.5 km. maximum.

Some seamounts form atolls with lagoons with a pass opening to the ocean, like Fanning, Palmyra and Caroline Islands. Others form low and flat islands, like Jarvis, Vostok, Flint ... the Christmas and Johnston Islands, the highest, have only dunes up to 12 m.

Jarvis Island - the coral island and its fringing reef - note the shallow ocean shelf on the right - photo Nasa 2005

Jarvis Island - the coral island and its fringing reef - note the shallow ocean shelf on the right - photo Nasa 2005

Position of the Line islands among the Pacific island chains. - Doc. Tulane University

Position of the Line islands among the Pacific island chains. - Doc. Tulane University

The Line Islands are part of United States Minor Outlying Islands, and the Kiribati group. Geographically, they are divided into Northern, Central and Southern Line Islands.

On ten islands and atolls, only three are currently inhabited: Christmas, Tabueran and Teraina, for a total of about 9,000 inhabitants.

Maps of Jarvis island - a clic to enlarge.Maps of Jarvis island - a clic to enlarge.

Maps of Jarvis island - a clic to enlarge.

Jarvis island - bathymétrie multibeam 3D - doc.PIBHMC / Hawaii Manoa University..

Jarvis island - bathymétrie multibeam 3D - doc.PIBHMC / Hawaii Manoa University..

Unlike most of the atolls, only exposed at low tide, Jarvis Island has a "dry" reef platform , where large deposits of guano are accumulated.

This coral island has an area of 4.5 km ², and its highest eight meters above water level issue.

The soil consists mainly of coral sand, and is home to only rare grasses and low shrubs. The outside edges of fringing reefs are bordered by steep slopes, except on the East Coast, where a shallow plateau (less than 20 meters) extends from 500 to 1000 meters. The habitat is favorable for wildlife and seabirds. The island has no fresh water point, or port.

Jarvis sign prohibiting the enter - Jarvis island Wildlife refuge.

Jarvis sign prohibiting the enter - Jarvis island Wildlife refuge.

Jarvis island - above: Coral / Jarvis Island National Wildlife Refuge - Photo credit USFWS, Jim Maragos - - below: Porites colony, massive and fingered corals, biobuilders, involved in the construction of reefs. (in the insert, rings of growtj) - doc.http: //www.lgt.lt
Jarvis island - above: Coral / Jarvis Island National Wildlife Refuge - Photo credit USFWS, Jim Maragos - - below: Porites colony, massive and fingered corals, biobuilders, involved in the construction of reefs. (in the insert, rings of growtj) - doc.http: //www.lgt.lt

Jarvis island - above: Coral / Jarvis Island National Wildlife Refuge - Photo credit USFWS, Jim Maragos - - below: Porites colony, massive and fingered corals, biobuilders, involved in the construction of reefs. (in the insert, rings of growtj) - doc.http: //www.lgt.lt

Discovered in 1821 by Captain Brown, commander of the ship Eliza Francis, owned by the Jarvis family, it was proclaimed in 1856 by the United States in the Guano Act, a federal law that allows American citizens to take possession of the uninhabited and unclaimed guano islands... but giving no obligation once the operation stopped. The guano deposits were mined from 1857 to 1879. Annexed by the British in 1889, it was claimed in 1935 by the United States. It is not permanently inhabited, and the few settlers were evacuated during the second world war. The only remnants of the occupation are a small lighthouse and the remains of the  Guano tramway. In 1974, Jarvis Island National Wildlife Refuge, including 5.15 square kilometers of land and 1,734 square kilometers of marine area, was created and integrated in 2009 in the Pacific Remote Islands Marine National Monument.

Jarvis Island: left , the lighthouse on the west coast / Joann94024 - right photo: remains of the Guano tramwayJarvis Island: left , the lighthouse on the west coast / Joann94024 - right photo: remains of the Guano tramway

Jarvis Island: left , the lighthouse on the west coast / Joann94024 - right photo: remains of the Guano tramway

White tern / Jarvis island

White tern / Jarvis island

Jarvis is home to 14 species of breeding seabirds including boobies, masked,brown or red-footed, frigates, brown and blue noddies, shearwaters, tropicbirds of  whiteTern ... not to mention the small waders, curlews, plovers and turnstones. Its colony of sooty terns is one of the largest in the world, with one million people.

 

Sources:

- Geology and geochronology of the line islands - Schlanger - 2012 - Journal of Geophysical Research  Solid Earth (1978–2012) -

- Center for coastal and ocean mapping / Joint Hydrographic center – Line islands - link

- Pacific Remote Island Area (PRIA) - link

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

The massive of Kondyor form, seen from space, a perfectly circular crater 8 km. in diameter, the peripheral ring peaks between 1200 and 1400 meters, and overlooks of a few hundred meters the Aldan Shield, in the extreme east of Siberia, near the Sea of ​​Okhotsk. A river flows from the north side of the massif, fed by rainwater collected in the crown; it cuts the massif by a present before the first fruits of its flow channel, called  "superimposed topography" phenomenon.

The massive of Kondyor - Doc. Credit: Jesse Allen. Data courtesy of GSFC / METI / ERSDAC / JAROS and the US / Japan Aster Science Team

The massive of Kondyor - Doc. Credit: Jesse Allen. Data courtesy of GSFC / METI / ERSDAC / JAROS and the US / Japan Aster Science Team

The massive of Kondyor - Landsat

The massive of Kondyor - Landsat

It is, however, neither a volcanic caldera , neither an impact crater !

His crown result of the erosion of a dome of sedimentary rocks metamorphised at high temperature, the apex of a mantle diapir that would have crossed the lithosphere to reach the Earth's surface. A field campaign, organized by the team of Jean-Pierre Burg, ventures between INSU and ETH-Zürich, confirmed this translithospheric diapirisme.

Mineralogical composition evolves from a core composed of dunite, olivine-rich rocks dominant in the upper mantle, until a halo of rocks where pyroxene dominates.

 The massive of Kondyor, seen from helicopter - photo Mcvld at ru.wikipedia

The massive of Kondyor, seen from helicopter - photo Mcvld at ru.wikipedia

 Geological map of cross section of the massive of  Kondyor - according Orlova (1992)), Zemlyanukhin & Prikhodko (1997) and Burg et al (2008)

Geological map of cross section of the massive of Kondyor - according Orlova (1992)), Zemlyanukhin & Prikhodko (1997) and Burg et al (2008)

This amazing natural landscape proves to be source of platinum and gold, operated by Russian mining companies. Large crystals of a Pt-Fe alloy, gold coated, are a feature of the deposits.

Furthermore, the presence of konderite, a mineral containing copper, platinum, iridium, rhodium, lead and sulfur, allowed the geologists to deduce the formation processes.

 

Massive of  Kondyor - Platinum nugget - photo Alchemist-hp

Massive of Kondyor - Platinum nugget - photo Alchemist-hp

Analysis of zircon crystals allows a dating reflecting a long evolution of the platinum-bearing dunite, between 2477 Ma and 143 Ma. Age of ancient zircons indicates an age of metamorphism at the edge of the Archean and Proterozoic (about 2.5 Ga). The age of the youngest zircon is linked to tectonico-magmatic activation of the Aldan shield at the time.

This structure would not be a simple curiosity of nature, according to the study of the CNRS, but the witness of a more general process, perhaps related to the initiation of rupture of continents.

 

Sources :

- Nasa Jet Propulsion Laboratory - Photojournal - Kondyor massif Russia

- Journal of Petrology - Translithospheric Mantle Diapirism: Geological Evidence and Numerical Modelling of the Kondyor Zoned Ultramafic Complex (Russian Far-East)  - par J-P. Burg & al.

- CNRS - Quand le manteau remonte à fleur de Terre en Sibérie

 - The age of Kondyor massif dunites (Aldan Province, Russia): First U-Pb isotopic data – par K.N.Malitch & al

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
Suwanose-jima, for the NE - left of the photo, Sakuchi caldera (center of the island) - right, the volcano Tondashidake - photo H. Seo / Geological Survey of Japan

Suwanose-jima, for the NE - left of the photo, Sakuchi caldera (center of the island) - right, the volcano Tondashidake - photo H. Seo / Geological Survey of Japan

Suwanose-jima in fact consists of the coalescence of four volcanic body, often seen and referred as volcanoes :  Tondashi-dake, Suzaki, O-take-dake and Negami, oriented in a NE-SW axis. They form a long island, 9 km on its longest axis, peaking at 799 meters.

Although it is unknown to the general public, he is one of the most active volcanoes in Japan, like its neighbor, Sakura-jima.

 

Suwanos-jima, southern view - photo H. Seo / Geological Survey of Japan

Suwanos-jima, southern view - photo H. Seo / Geological Survey of Japan

South of the island, a sequence presents rhyolitic pumice deposits 3 m thick, and a pyroclastic deposit from a height of 15 meters, both having an insular source. They have over 23,000 years, as they are covered by the "ashes AT" from the eruption of Aira caldera, located well north (and encompassing the modern Sakurajima).

These ancient eruptions are superior in magnitude
to that historical time, characterized by frequent but moderate eruptions of slag. They concern andesitic-basaltic lavas of andesitic nature.
 

Suwanos-jima - to the left, simplified map of the volcanic units / Photovolcanica - to the right, topographic map with the different craters, whose Otake (Oc) and caldera Sakuchi - doc Taketo Shimano 2008 - one click to enlarge Suwanos-jima - to the left, simplified map of the volcanic units / Photovolcanica - to the right, topographic map with the different craters, whose Otake (Oc) and caldera Sakuchi - doc Taketo Shimano 2008 - one click to enlarge

Suwanos-jima - to the left, simplified map of the volcanic units / Photovolcanica - to the right, topographic map with the different craters, whose Otake (Oc) and caldera Sakuchi - doc Taketo Shimano 2008 - one click to enlarge

In 1813-1814, the eruption "Bunka", of VEI 4, is characterized by significant tephra deposits on the island, issuing of two andesitic flows starting from the crater SO, that have elapsed until to the west coast. At the end of the eruption, a sector collapse won the NE summit crater "Otake", created a huge debris avalanche and formed the caldera ironhorse shaped Sakuchi, which extends to the east coast. After the eruption, the island was abandoned for 70 years.

The eruption 1884-85was less powerfull, resulting in an outpouring of lava, known as Meiji casting, which reached the East Coast.

Suwanose-jima: Sakuchi caldera and Otake crater in 2005 - photo H. Seo / Geological Survey of Japan

Suwanose-jima: Sakuchi caldera and Otake crater in 2005 - photo H. Seo / Geological Survey of Japan

Since 1985, eruptions have as seat the summit crater northeast, the O-take and are Strombolian to Vulcanian kind. The most recent in 2001-2003 and 2004-2014 ... JMA reported explosions in June 2014.

Access to the top of Suwanose-jima is regulated by the park administration, and often banned because of the risk of ballistic projectiles and electrostatic discharge. A closet marks the entrance to the restricted area. The access path, abandoned, is severely eroded in places and covered with vegetation.

Suwanose-jima - and eruption plume 05.07.2009 - Doc. NASA MODIS Aqua

Suwanose-jima - and eruption plume 05.07.2009 - Doc. NASA MODIS Aqua

Ryukyu volcanic arc - 4 - Suwanose-jima.
Suwanose-jima - November 5, 2009 - phot N. Geshi / Geological Survey of Japan

Suwanose-jima - November 5, 2009 - phot N. Geshi / Geological Survey of Japan

Suwanose-jima - strombolian activity - photo Thorsten Boeckel / December 2009-January 2010

Suwanose-jima - strombolian activity - photo Thorsten Boeckel / December 2009-January 2010

Sources :

- Geological survey of Japan – Suwanose-jima

- Global Volcanism Program – Suwanosejima

- Photovolcanica - Suwanosejima

- Thorsten Boeckel – Japan : Kyushu and Tokara islands 25.12.2009/09.01.2010 - link

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
 Dawn on Nakanoshima - phot 名古屋 太郎

Dawn on Nakanoshima - phot 名古屋 太郎

Further south in the Tokara Islands is Nakano-shima, a volcanic island 9 km out of 5, surrounded by coral reefs.

The older Sakiwaridake volcano, south of the island is separated by a narrow plateau, with an elevation of 200 meters, from the active andesitic cone On-take, which forms the northern half of Nakanoshima
.

.
 

Nakanoshima and volcano On-take, under an umbrella of cloud - in the background, Kuchinoshima volcano - photo H. Seo / Geological Survey of Japan

Nakanoshima and volcano On-take, under an umbrella of cloud - in the background, Kuchinoshima volcano - photo H. Seo / Geological Survey of Japan

The rocks component Nakanoshima consist in andesites Serikazi to SE (dated 1.75 +/- 0.22 Ma), in andesites Nanatsuyama to E, in andesites Sakiwaridake and Shiizaki to SW, in andesites Nigoriura (dated 0.14 +/- 0.06 Ma) and Negamidake and the formations of the old and young volcano Otake. Dating rocks is therefore up to the start of the activity in the Pleistocene.

 Nakanoshima - the On-take volcano - photo H.Seo / Geological Survey of Japan 2005

Nakanoshima - the On-take volcano - photo H.Seo / Geological Survey of Japan 2005

Nakanoshima - the summit crater of the volcano On-take - photo H.Seo / Geological Survey of Japan 2005

Nakanoshima - the summit crater of the volcano On-take - photo H.Seo / Geological Survey of Japan 2005

The On-take stratovolcano has a summit crater, 500 meters wide, which is partially filled with water in the rainy season.

Single eruption reported during the historical period, a small phreatic eruption marked the summit crater in January 1914. An ash plume is indicated, subject to reserve, in October 1949.

Solfataras are present at the top and in the explosion crater on the side of NE. Sulfur deposits have been exploited until late 1944.
Hot springs are welling up in three places to Funakura.

The crater of the volcano Otake Nakanoshima - photo 名古屋 太郎

The crater of the volcano Otake Nakanoshima - photo 名古屋 太郎

 Nakanoshima - solfatara on the side of One E-take - photo H.Seo / Geological Survey of Japan

Nakanoshima - solfatara on the side of One E-take - photo H.Seo / Geological Survey of Japan

Nakanoshima - Emissions of bubbles off the island testify to the volcanic activity of this area - photo Geoff H / Scubaboard

Nakanoshima - Emissions of bubbles off the island testify to the volcanic activity of this area - photo Geoff H / Scubaboard

Sources :

- Geological Survey of Japan – Nakanoshima

- Global Volcanism Program – Nakanoshima

- Journal of Geoscience – Osaka University – Volcanic geology and rocks of nakanoshima, Tojara islands – by Masahiro Daishi.

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
The volcanic arc and the Ryukyu Trench - Doc. Google earth annotated

The volcanic arc and the Ryukyu Trench - Doc. Google earth annotated

Kuchino-shima is located in the north of the islands forming the Ryukyu volcanic arc, between Nakano-shima and Kuchinoerabu-shima.

 

The small population is concentrated in the north of this tiny land 3 km. on 7, in the villages of Nishinohama and Kuchinoshima.
 

Kuchino-shima - photo H. Seo / Geological Survey of Japan

Kuchino-shima - photo H. Seo / Geological Survey of Japan

Two andesitic stratovolcano and a chain of lava domes, oriented NW-SE, characterize it. The composite dome Maedake highest point 628 meters, stood at the east of the summit of the flat roof  stratovolcano Yokodake top of 501m.

The Global Volcanism Program reports only four eruptions, in 6750 BC, in 900 BC, in 750 and one in 1190. In 2001, discoloration of the ocean indicate always thevolcanic activity.

Kuchino-shima - Lava Dome Maedake seen from E (Toshiri-Kaigan). - Photo S.Nakano / GSJ

Kuchino-shima - Lava Dome Maedake seen from E (Toshiri-Kaigan). - Photo S.Nakano / GSJ

Kuchino-shima - in the center, the lava Dome Maedake seen from north , the stratovolcano Yokodake on the right - photo S.Nakano 2005 / GSJ

Kuchino-shima - in the center, the lava Dome Maedake seen from north , the stratovolcano Yokodake on the right - photo S.Nakano 2005 / GSJ

Among the many domes, the dome Moedake has an explosion crater still emitting fumaroles.

Kuchino-shima - the explosion crater of the dome Moedake seen from the  N - photo H. Seo / GSJ

Kuchino-shima - the explosion crater of the dome Moedake seen from the N - photo H. Seo / GSJ

 Kuchino-shima - Activity fumaroles in the crater of explosion of dome Moedake - Photo S. Nakano / GSJ

Kuchino-shima - Activity fumaroles in the crater of explosion of dome Moedake - Photo S. Nakano / GSJ

The island is home to indigenous cattle in small number, retaining the characteristics of the oldest breeds of Japan described in ancient documents, the Kuchinoshima Ushi. They are thin (300-400 kg), small sizes, with a broad chest and a tiny waist.

 

Sources :

- Geological Survey of Japan - Quaternary volcanoes - Kuchino-shima

- Global Volcanism Program - Kuchinoshima

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

Back to the south of the Nippon archipelago and the islands Tokara, starting with the island of Kuchinoerabu-jima, which is illustrated on August 3 with a brief and violent eruption.

The site of the eruption was the Shin-dake crater. The eruption lasted about ten minutes, characterized by rising of an ash plume to 1,500 meters and a pyroclastic flow on the western flank of the volcano, characterized by hot gases and steam that burned vegetation ...  index of a likely phreatic nature eruption . The volcanic seismicity and tremor began to drop on August 5, leaving a small steam plume above the crater rim. (JMA)

 

Eruption of Kuchinoerabu-jima on 03/08/2014 - the pyroclastic cloud is surmounted, on the left, by the eruption plume - photo Kuchi-erabu.org

Eruption of Kuchinoerabu-jima on 03/08/2014 - the pyroclastic cloud is surmounted, on the left, by the eruption plume - photo Kuchi-erabu.org

Kuchinoerabu-jima - Above,the trace of the pyroclastic flow is visible on the left, between the top and the sea - It cuts a circular route - on the plate bottom, a vegetation area burned - photos Japan Coast Guard 06.08.2014
Kuchinoerabu-jima - Above,the trace of the pyroclastic flow is visible on the left, between the top and the sea - It cuts a circular route - on the plate bottom, a vegetation area burned - photos Japan Coast Guard 06.08.2014

Kuchinoerabu-jima - Above,the trace of the pyroclastic flow is visible on the left, between the top and the sea - It cuts a circular route - on the plate bottom, a vegetation area burned - photos Japan Coast Guard 06.08.2014

Kuchinoerabu-jima - Crater on 06/08/2014 at an aerial survey by the Japan Coast Guard

Kuchinoerabu-jima - Crater on 06/08/2014 at an aerial survey by the Japan Coast Guard

The eruption opened a crack on the top of the Shin-dake, observed on August 6 during an aerial survey by Japanese volcanologists.

 

Kuchinoerabu-jima - pictures during an overflight  : above, on 06/08/2014 and down, o, 19.12.2011, show the opening of a summit crevasse - Doc. Japan Coast Guards

Kuchinoerabu-jima - pictures during an overflight : above, on 06/08/2014 and down, o, 19.12.2011, show the opening of a summit crevasse - Doc. Japan Coast Guards

The island of Kuchinoerabu consists of different age spread buildings.

Although the beginning of the eruption is unknown, the first building is the Gokyo volcano that emerged 580,000 years ago. The volcano Jogahana, a contemporary of Gokyo is exposed on the north coast of the island., while Ban'yagamine, dated about 200,000 years, shaped the northwest. Then the more recent volcanoes formed the east-central part of Kuchinoerabu: they call Takadomori (100,000 years), Kashimine, Noike, Hachikubo, Furudake and Shindake. Two large pyroclastic eruptions are involved in the formation of volcanoes and Noike Furudake between 15,000 and 11,000 years ago.

The latter three are responsible for the volcanic activity during the Holocene; Shindake focuses on the historical activity.

Kuchinoerabu-jima - photo Geological Survey of Japan

Kuchinoerabu-jima - photo Geological Survey of Japan

Kuchinoerabu-jima - location of various volcanoes - doc.Geological Survey of Japan

Kuchinoerabu-jima - location of various volcanoes - doc.Geological Survey of Japan

Kuchinoerabu-jima - the most recent craters and lava flows - doc.Geological Survey of Japan

Kuchinoerabu-jima - the most recent craters and lava flows - doc.Geological Survey of Japan

The Shindake:

The Shindake began to build in the escarpment of the partial collapse of Furudake, dating back thousands of years. The volcano consists of lava erupting during the 9 and 11 centuries, and a summit pyroclastic cone of explosion breccias,  products of a vulcanian and a phreatic to phreatomagmatic activity at the summit crater.

The central crater is surrounded by some satellite craters, some of which were opened during the eruption of 1930. In 1931 and 1933 to 1934, violent eruptions were accompanied by lahars spread along the river Mukaehama. A crack 500 m long, oriented NS, opened on the east slopes of Shindake, and was the seat of the eruptions of 1945 and 1980.

 

Evolution of volcanoes Furudake and Shindake between 13,000 years BP and today - doc.Geological Survey of Japan / AIST

Evolution of volcanoes Furudake and Shindake between 13,000 years BP and today - doc.Geological Survey of Japan / AIST

Kuchinoerabu-jima - Shindake crater and fissure of the eruption 1980 - doc.JMA

Kuchinoerabu-jima - Shindake crater and fissure of the eruption 1980 - doc.JMA

 Kuchinoerabu-jima - fisssurale Eruption of Shindake - photo 10.10.1980 / doc.JMA

Kuchinoerabu-jima - fisssurale Eruption of Shindake - photo 10.10.1980 / doc.JMA

In September 1980, a short and very powerful explosion produced a small plume and ash falls, mainly over the sea; it was followed by emissions of white vapor during a few days.

Since 1980, an increase in seismic and thermal activity around the summit crater was reinforced by the rise of hydrothermal fluids from a reservoir located 500 meters below the summit.

Seismic swarms and inflation were observed in January 2005; the inflationary source is located several hundred meters below the crater. The fumarolic activity has been increasing since.

 

Sources :

- Geological Survey of Japan / Active volcanoes of Japan - Kuchinoerabu-jima

- Global Volcanism Program -  Kuchinoerabujima  

- JMA - Kuchinoerabujima

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

The production of stamps through theme by the Azores archipelago is large and diverse, as is the case for most of the islands.

By focusing on the theme of volcanoes, here are some examples created in recent decades.

- The fiftieth anniversary of the eruption of the
Capelinhos - 2007

Stamp and commemorative plate from the eruption of Capelinhos 1957 - 2007 issue

Stamp and commemorative plate from the eruption of Capelinhos 1957 - 2007 issue

Stamps from the eruption of Capelinhos 1957 - 2007 issue

Stamps from the eruption of Capelinhos 1957 - 2007 issue

Faial, eruption of Capelinhos - Espólio do T. C. José Agostinho- Museu de Angra do Heroísmo - Siaram

Faial, eruption of Capelinhos - Espólio do T. C. José Agostinho- Museu de Angra do Heroísmo - Siaram

Stamp and commemorative plate from the eruption of Capelinhos 1957 - 2007 issue

Stamp and commemorative plate from the eruption of Capelinhos 1957 - 2007 issue

- The fajãs, Portuguese term refers to platforms or deltas built above the tide level by landslide and / or lava flows, are widely distributed in the Azores, especially on the island of São Jorge.

Fajãs : Caldera de Santo Christo / São Jorge - 2012 issue.

Fajãs : Caldera de Santo Christo / São Jorge - 2012 issue.

 fajãs : Fajã dos Cubres / São Jorge -  2012 issue.

fajãs : Fajã dos Cubres / São Jorge - 2012 issue.

Fajã dos Cubres / São Jorge - photo Alberto Garcia

Fajã dos Cubres / São Jorge - photo Alberto Garcia

- The geothermal areas and geothermal exploitation were also honored.

Hot spring on São Miguel -  2005 issue.

Hot spring on São Miguel - 2005 issue.

São Miguel - caldera das Furnas : source chaude - photo Geoparque Azores

São Miguel - caldera das Furnas : source chaude - photo Geoparque Azores

Exploitation of geothermal energy - issue 1983

Exploitation of geothermal energy - issue 1983

- Nature is also being honored with this endemic bird of the laurel forest of São Miguel : the "Priolo", the Azores Bullfinch / Pyrrhula murina.

 Priolo,  endemic bird de São Miguel -  2008 issue.

Priolo, endemic bird de São Miguel - 2008 issue.

 The Azores Bullfinchphoto Ciência / Portugal

The Azores Bullfinchphoto Ciência / Portugal

Sources :

- Catawiki

- Delcampe.net

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
Flores / Azores - Baia Alagoa Cedros - photo Angrense

Flores / Azores - Baia Alagoa Cedros - photo Angrense

The island of Flores, 10 km. 5, was formed during the Pleistocene, with the growth of a submarine volcano, and explosive activity associated with the formation of small calderas and many cones and craters.
After a long rest period of 200,000 years, young craters of phreatomagmatic eruptions and lava flows were produced during the Holocene.

Flores / Azores - Rocha dos Bordes - photo siaram casacacorianas

Flores / Azores - Rocha dos Bordes - photo siaram casacacorianas

Flores / Azores - Rocha dos Bordes, under evening light - photo Visitazores

Flores / Azores - Rocha dos Bordes, under evening light - photo Visitazores

One of the most famous natural monuments Azores, the Rocha dos Bordões, is a set of vertical basaltic organs. This disjunction prismatic, in relation to a mugearite flow, dated 570,000 years, suddenly appeared on top of an elevation. Partially covered with mosses, lichens and other vegetation, the basalt stone changes colors during the day ... to see these changes, the Rocha dos Bordões requires repeated visits at different times of day.

 

Flores / Azores - The Lagoa Funda & Rasa - photo Helena Rodrigues / Açores.net

Flores / Azores - The Lagoa Funda & Rasa - photo Helena Rodrigues / Açores.net

Calderas Rasa and Funda de Lajes were formed there 3150 years.These depressions are two explosions craters associated with hydromagmatic eruptions based in the mountains of southern sector of Flores. They are occupied by lakes and located at different altitudes. The eruption of the caldera Funda, a tuff ring, was accompanied by lava flow towards the southeast, reaching the coast at Lajes.

 Flores maps - in the center, the caldera Branca, Seca, Comprida and Negra - south, the calderas Funda & Rasa - a click to enlarge.  Flores maps - in the center, the caldera Branca, Seca, Comprida and Negra - south, the calderas Funda & Rasa - a click to enlarge.

Flores maps - in the center, the caldera Branca, Seca, Comprida and Negra - south, the calderas Funda & Rasa - a click to enlarge.

More central to the "Island of Flowers", there are four calderas, deriving from explosions of maars, in connection with hydromagmatic eruptions on the central plateau: the calderas Branca, Seca, Comprida and Negra.

Except caldera Seca, they are occupied by lakes. The caldera Negra is 108 meters deep which makes its waters dark, and earned him his name. Caldera Comprida, a tuff ring in the caldera Seca, is dated of 2,900 years. It produced a lava flow, heading north-west,  joined the coast to Faja Grande.

Isolated from others, Caldeira da Lomba is surrounded by a small rise and bouquets of hydrangeas.
Agua Quentes is a collection of hot and sulfur springs.



Flores / Azores - Caldera Seca - photo Geoparque Azores

Flores / Azores - the calderas Negra and Comprida - photo Geoparque Azores

Flores / Azores - the calderas Negra and Comprida - photo Geoparque Azores

 Flores / Azores - Caldera Seca - photo Geoparque Azores

Flores / Azores - Caldera Seca - photo Geoparque Azores

Craters, lakes and rivers mark the island landscape. The river water short quietly on the surface of the central plateau, or cascade in many falls and winds along broad and deep valleys. Before flowing into the ocean, it gives strength to the various hydroelectric turbines on the island.

Area of  Faja Grande - Fajãzinha is one of the most beautiful coastal landscapes of the Azores. On the vast green wall that borders this area can be observed almost twenty waterfalls, including that of Ribeira Grande, which rushes a jump of 300 meters. At the base of the slope, there are various permanent water bodies, such as
Poço do Bacalhau or Poço da Alagoinha, also known as Duck Lake.

Flores / Azores - Faja Grande - photo Geoparque Azores

Flores / Azores - Faja Grande - photo Geoparque Azores

Flores / Azores - Faja Grande - photo Geoparque Azores

Flores / Azores - Faja Grande - photo Geoparque Azores

Countless islands, points, shoals, inlets, coastal caves, disjunctions prismatic, waterfalls and shady valleys are some of the features offered by the coastal strip of Flores. TheFajã Nova, to Ponta da Rocha Alta, and Fajã de Lopo Vaz form the high cliffs of the south coast, accessible by a footpath that runs along the cliff.

The north side of the island, and linear low coastal cliffs between Ponta Delgada and Ponta do Albarnaz gives way to impassable reliefs of the north-east coast, only crisscrossed by hiking trails, such as the one from the lighthouse to Albarnaz to Ponta da Faja, a difficult journey rewarded with spectacular views ..

Conversely, in the lava fajãs Santa Cruz, Lajes and
Fajã Grande, sea softly embraces the low rocky peaks of black lava and lets see, in calm weather, the wildlife of the seabed.

Near the promontory of Ponta da Caveira, Gruta dos Enxaréus forms a cavity 50 meters long and 40 m high, including 15 m underwater.

 

Flores / Azores - landscape of fajãs / lava deltas

Flores / Azores - landscape of fajãs / lava deltas

Flores / Azores - Gruta dos Enxaréus - photo time to go

Flores / Azores - Gruta dos Enxaréus - photo time to go

The Ilhéu de Monchique, 1.5 km. off, form the ultimate point of Europe to the west, before the expanses of the Atlantic. At the time when navigation depended solely on astronomical data, the island was an important point of reference for the calibration of instruments of  marine navigation.
 

Flores / Azores - the Ilheu do Monchique - photo Dreizung

Flores / Azores - the Ilheu do Monchique - photo Dreizung

Sources :

- Geoparque Azores - Flores

- Global Volcanism Program - Flores

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

The small island of Corvo is located north of Flores in the western part of the archipelago.
With an area of ​​17.12 km ², it is inhabited by some 500 people, mostly gathered in the city of Vila do Corvo, to the south.

Albeit isolated, Corvo has been the target of attacks by pirates and privateers. In exchange for protection, the island has allowed them to find a place of supply, care for the crews and repair of vessels. It was nevertheless sacked by English privateers in 1587.

 

Corvo / Azores - the south side of the island with Vila do Corvo - photo Dreizung

Corvo / Azores - the south side of the island with Vila do Corvo - photo Dreizung

These two islands emerge from the same submarine bench oriented NNE-SSW, anchored on the North American tectonic plate, to the west of the Mid-Atlantic Ridge.

Corvo, a volcano central type, began to emerge from 730,000 years; the central cone was estimated to peak at 1,000 meters before its collapse there 430,000 years ago.


 

Tectonic Sitauation of Flores-Corvo group west of the Mid-Atlantic ridge.

Tectonic Sitauation of Flores-Corvo group west of the Mid-Atlantic ridge.

The subaerial activity phase is first marked by a basaltic volcanism, before moving to trachytic eruptions, most explosive, including some linked to the formation of the caldera. Then, the activity return to a basaltic volcanism, with Hawaiian and Strombolian eruptions. The most recent episodes form the cinder cone of Coroinha.

Corvo / Azores - the Caldeirão Monte Gordo - photo Angrese.

Corvo / Azores - the Caldeirão Monte Gordo - photo Angrese.

Corvo / Azores - the Caldeirão Monte Gordo - cultivated fields lining the inner walls of the caldera - photo José Luis Ávila Pedro Noronha e Silveira Costa

Corvo / Azores - the Caldeirão Monte Gordo - cultivated fields lining the inner walls of the caldera - photo José Luis Ávila Pedro Noronha e Silveira Costa

Monte Gordo sees its western edge truncated by wind and marine erosion. A cliff of 700 meters is forming above the ocean.
Its caldera, the Caldeirão, off 2,000 meters is occupied by cinder cones, intrusion vein, two permanent lakes and other ephemera.

 

permanent lakes and other ephemera. Corvo / Azores - the Caldeirão - photo Geoparque Azores

permanent lakes and other ephemera. Corvo / Azores - the Caldeirão - photo Geoparque Azores

Corvo / Azores - the Caldeirão - photo Geoparque Azores Corvo / Azores - the Caldeirão - photo Siaram

Corvo / Azores - the Caldeirão - photo Geoparque Azores Corvo / Azores - the Caldeirão - photo Siaram

 Corvo maps - a click to enlarge  Corvo maps - a click to enlarge

Corvo maps - a click to enlarge

The slopes of the volcano are partially preserved in the east and south, where secondary cones are preserved from erosion. Morro da Fonte,  Grotão do Castelhana and Coroa do Pico are responsible of basaltic flows that formed the fajã lavica, a lava delta high of 10-60 meters.
 

Corvo / Azores - Lava Delta / fajã lavica, to  the south of Corvo, houses the airstrip and houses - photo Geoparque Azores

Corvo / Azores - Lava Delta / fajã lavica, to the south of Corvo, houses the airstrip and houses - photo Geoparque Azores

Northwest of the island, small ilets,  ilhéu dos Torrais and Ilhéu do Torrão, and submerged reefs make the navigation perilous near the coast.
 

Corvo / Azores - Ponta do Marco - photo Geoparque Azores

Corvo / Azores - Ponta do Marco - photo Geoparque Azores

Corvo landscape is characterized by dark stone walls dividing the properties. Paillers walls of basalt, used for storage of feed and tools, enhance the dark and austere landscape appearance and earned the nickname of Corvo, "the black island" . Green pasture is combined with the color of juniper and grain plantations.

To Ponta Negra, south of Corvo, small windmills, conical trunk, deploying sails and dot the horizon of white. The wooden dome can be rotated to orient the wings depending on the wind direction. They are used to grind grain and corn.


 

Corvo / Azores - the basalt walls - photo ATA

Corvo / Azores - the basalt walls - photo ATA

Corvo / Azores - moinhos to the south of the island- in the background, Flores Island - photo Moinhos açorianos

Corvo / Azores - moinhos to the south of the island- in the background, Flores Island - photo Moinhos açorianos

Sources :

- CVARG / Centro de Vulcanologia e Avaliação de Riscos Geológicos - link

- Geoparque Azores - link

- Global Volcanism Program - Corvo

- DIAS, J. (2001) – Geologia e tectónica da ilha do Corvo (Açores-Portugal): Contributos para o ordenamento do espaço físico. - Tese de Mestrado. Universidade de Coimbra.

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

Located in the central area of ​​the Volcanic Complex dos Picos, characterized by 200 cinder cones and a fissural volcanism, Gruta do Carvão is the largest lava tube on São Miguel, with a total length of 1,250 meters, in two separate sections.

This tunnel extends within a basalt flow, north-south, and reaching the sea west of Ponta Delgada.
 

Azores - São Miguel - Gruta do Carvão - photo page Facebook / Gruta do Carvão

Azores - São Miguel - Gruta do Carvão - photo page Facebook / Gruta do Carvão

Map of volcanic areas of São Miguel - the dos Picos Volcanic Complex is colored gray with the position of the various caves / lava tubes (black triangles and points)

Map of volcanic areas of São Miguel - the dos Picos Volcanic Complex is colored gray with the position of the various caves / lava tubes (black triangles and points)

Its average height is 2-3 meters, with passages reaching more than 5 meters. Its width varies significantly, with a maximum above 10 meters, particularly at the intersection of several branches.

A stretch of 200 meters is characterized by the superposition of two tunnels having sinkholes. In some sections, runoff waters deposited sediment, with an average height of one meter.

Azores - São Miguel - Gruta do Carvão - photo Diogo Caetano / Amigos dos Açores - amigosdosacores@amigosdosacores.pt

Azores - São Miguel - Gruta do Carvão - photo Diogo Caetano / Amigos dos Açores - amigosdosacores@amigosdosacores.pt

Azores - São Miguel - Gruta do Carvão - photo page Facebook / Gruta do Carvão

Azores - São Miguel - Gruta do Carvão - photo page Facebook / Gruta do Carvão

Azores - São Miguel - Gruta do Carvão - photo page Facebook / Gruta do Carvão

Azores - São Miguel - Gruta do Carvão - photo page Facebook / Gruta do Carvão

Lava stalactites hang from the ceiling, sometimes covered with a whitish hue brought by runoff. The walls have "bolhas de gás", bubbles that have burst under the pressure of gas.
 

 Azores - São Miguel - Gruta do Carvão - photo Diogo Caetano / Amigos dos Açores - amigosdosacores@amigosdosacores.pt

Azores - São Miguel - Gruta do Carvão - photo Diogo Caetano / Amigos dos Açores - amigosdosacores@amigosdosacores.pt

Azores - São Miguel - Gruta do Carvão - photo Guardar foto - Siaram

Azores - São Miguel - Gruta do Carvão - photo Guardar foto - Siaram

Basaltic lava is oxidized, giving it a reddish-orange hues along the cracks and areas of infiltration.

Azores - São Miguel - Gruta do Carvão: color of oxidized basalt - azoresphotos.blogspot.be

Azores - São Miguel - Gruta do Carvão: color of oxidized basalt - azoresphotos.blogspot.be

The age of this lava tube is between 5000 and 12000 years according to Carbon 14 dating and according to the analysis of deposits of pyroclastic material (ash and lapilli), possibly emitted by the volcano Sete Cidades of the Fogo, covering this cave.

 

Sources :

- Amigos dos Açores - associaçoa ecologica -link

-  Gruta do Carvão - Paim - link

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