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Earth of fire

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

excursions et voyages

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

To the North -east coast of Taiwan, Kueishantao island , also known as the Turtle mountain island (name of his profile view of the Big Island ), or Guieshan island, is part of a group of five small volcanic islands .

Guieshan island / Taiwan - a large area of discolored water is evidence of volcanic underwater activity - photo Chen Minming

Guieshan island / Taiwan - a large area of discolored water is evidence of volcanic underwater activity - photo Chen Minming

Composed of andesite lava flows and volcaniclastic materials, the stratovolcano rises to 401 meters above sea level. Its area is 2,841 km ².

This island is the volcano located  the most south -west along the axis of the back-arc Okinawa Trough basin , which extends north-east of Taiwan to Unzen volcano on Japanese island of Kyushu .

Its last eruption date from 1785 according to the GVP ... which corresponds to historical writings from the time of King Qianlong of the Qing Dynasty ( 1775-1795 ) , in which reference is made to the opening of the Guieshan mountain and a red blood lava pouring.

Tectonic of the block Taiwan, involving the Eurasian plate and the oceanic plate Philipinnes - doc . Angelier 2001

Tectonic of the block Taiwan, involving the Eurasian plate and the oceanic plate Philipinnes - doc . Angelier 2001

The current activity consist in vigorous underwater fumaroles (see video below) and severe discoloration of the water.

Discolouration of the waters around the island Guieshan due to underwater fumaroles - photo eng.taiwan.net.tw

Discolouration of the waters around the island Guieshan due to underwater fumaroles - photo eng.taiwan.net.tw

The underwater hot springs reflect the volcanic activity, and are a justification for a "specialized tourism " - Vimeo / Kaiyun Cheng.

The local population consisted mainly of fishermen living on a  gravel and pebbles beach, surrounding a freshwater lake. Affected by the storms , this beach was subject to changes in topography, justifying the name of the island , " a turtle wagging tail ."

They were relocated in 1977 due to difficulties related to life on the island. From 1977 to 2000, Guieshan served as a military base , it is now a nature reserve zone and a tourist destination governed by many restrictions ( maximum 350 people per day).

"Turtle Island " - Guieshan has the shape of a turtle with a prominent tail. - Photo Chen Minming

"Turtle Island " - Guieshan has the shape of a turtle with a prominent tail. - Photo Chen Minming

Guieshan - the freshwater lake and the facilities on the " pebble beach" at the tip of the island - . Chen Photo Minming

Guieshan - the freshwater lake and the facilities on the " pebble beach" at the tip of the island - . Chen Photo Minming

Sources :

- Global Volcanism Program - Kueishantao

- un article en relation : Taïwan Today / Taipei quake sparks eruption of volcano interest - link

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
Olympus Mons - seen by Viking Orbiter I / 06/22/1978

Olympus Mons - seen by Viking Orbiter I / 06/22/1978

Located northwest of the Tharsis volcanic chain , Olympus Mons , the largest Martian volcano and the largest of all known volcanoes in the solar system , has maddening measurements:

It rises to 21,229 meters above the baseline of Mars , according to the latest laser altimeter measures made by the Mars Global Surveyor ( MOLA ) - previous measurements give higher altitudes, but based on a reference level now changed - his diameter is 624 km. And it is bordered by a large scarp 6,000 meters. Despite its impressive size , the slopes do not exceed 5-10 ° ... this shield volcano is extensive , and its area is approximately 500,000 km ² ... compared to the size of France , Olympus Mons covers most of the territory.

Comparative size between Olympus Mons and metropolitan France , to the left -  to the right, Comparative size and weight  between Olympus Mons, Hawaii and Mount Everest ( height / lenght is one in ten) - click on image to enlarge size Comparative size between Olympus Mons and metropolitan France , to the left -  to the right, Comparative size and weight  between Olympus Mons, Hawaii and Mount Everest ( height / lenght is one in ten) - click on image to enlarge size

Comparative size between Olympus Mons and metropolitan France , to the left - to the right, Comparative size and weight between Olympus Mons, Hawaii and Mount Everest ( height / lenght is one in ten) - click on image to enlarge size

Its summit caldera is about 80 x 60 km wide with a depth of 2000-3500 meters. Six caldera / craters are formed over a short period , there 400-150 Ma and partially overlap.

The largest and oldest seems to have originally formed by a single lava lake . The size of this caldera reflects the size of the underlying magma chamber, estimated position at 32 km. under the floor of the caldera. Each collapse and each caldera corresponds to a phase of volcanic activity .

On its sides , we notice the presence of some impact craters.

A rebuilding of Olympus Mons with the database of MOLA - doc.Brian Russo.

A rebuilding of Olympus Mons with the database of MOLA - doc.Brian Russo.

Olympus Mons caldera - doc. ESA / DLR -FU Berlin

Olympus Mons caldera - doc. ESA / DLR -FU Berlin

Summit caldera of Olympus Mons - age of their training Ma - Doc. Robbins et al. 2011

Summit caldera of Olympus Mons - age of their training Ma - Doc. Robbins et al. 2011

A wide annular depression ( moat ) 2,000 meters deep surrounds the base of Olympus Mons , presumably in connection with the enormous weight of the volcanic mass putting pressure on the crust of Mars. This depression is deeper northwest to the southeast .

Topographic map in color of Olympus Mons, the annular depression and surrounding land - doc . NASA / JPL -Caltech / Arizona State University

Topographic map in color of Olympus Mons, the annular depression and surrounding land - doc . NASA / JPL -Caltech / Arizona State University

The main difference between the volcanoes of Mars and the terrestrial volcanoes comes from their size , ten to one hundred times greater.

Two reasons:

- on earth, hotspots are stationary , and the tectonic plates move over , forming a chain of volcanoes. On Mars, the crust remains stationary , and the total volume of lava is not shared between different structures, but can be stacked to form a gigantic volcano.

- A lowest surface gravity on Mars allows Martian lava flows , forming the shield, a longer expansion.

 

Sources:

- Nasa / JPL-Caltech / Arizona State University

- Nature -  Recent and episodic volcanic and glacial activity on Mars revealed by the High Resolution Stereo Camera - G. Neukum, R. Jaumann, H. Hoffmann, E. Hauber, J. W. Head, A. T. Basilevsky, B. A. Ivanov, S. C. Werner, S. van Gasselt, J. B. Murray, T. McCord et l'équipe de l'expérience High Resolution Stereo Camera de la mission Mars Express.

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

Three other pyroclastic formations attributed to acid magma volcanoes mark the Limagne.

A first formation , CF5 named , was observed exclusively in the area of ​​Clermont- Ferrand ( Clermont Basin , Grand Marsh Limagne - area Gerzat ) .

It is a laminated ashy cream pastel pink which is a fallout of coarse ash of rhyolite composition. The volcano - source was identified by mineralogical studies : the crater Kilian (or the Puy de Vasset ) . However, this type of Pelean volcano has a crater because its dome was beheaded by violent vertical explosions . This eruption is dated about 9500 years , by palynology at the transition to the beginning of the Boreal - Atlantic.

The Kilian is located south of the Puy de Dôme, and his trachyte provided the blocks used in the construction of the Temple of Mercury - 2nd century, at the top of the Puy de Dome

Location of volcanoes around the Puy de Dôme - doc OPGC / Observatoire de Physique du Globe Clermont- Ferrand

Location of volcanoes around the Puy de Dôme - doc OPGC / Observatoire de Physique du Globe Clermont- Ferrand

Summit of the Puy de Dome and the Temple of Mercury - photo - earth element

Summit of the Puy de Dome and the Temple of Mercury - photo - earth element

The second formation corresponds to a level of ash, very similar in nature to CF5 , discovered in the lake filling the paleo- lake Sarliève . This new fallout was called Tephra of  Sarliève .

 

A third formation named CF7 has been recognized in several stratigraphic Limagne northeast , east and south of Clermont- Ferrand .

This is centimetric angular fragments of trachyte scattered in mostly beige silt level . The morphology of these fragments suggests that they are derived from the crust of a acid lava dome  . Its attribution to a specific volcano of Chaîne des Puys is being discussed although initial analyzes ( geochemistry and analysis of radionuclides ) indicate origin as the Puy de Clierzou neighboring the Puy de Dôme, north side.

The explosive violent episode is part of a historical complex : an incomplete ascent of magma  ... during this, the trachy - andesitic lava is not emitted to the air, then an explosion that blew the lava plug formed and an infiltration of trachytic lava in the ashes and the solidification of the mixture.

The CF7 training was highlighted in archaeological levels of Sauveterrian age.(Mesolithic ) .

Puy de Clierzou and caves - photo LPJ

Puy de Clierzou and caves - photo LPJ

The habitats of Limagne have been affected by at least four trachytic eruptive episodes of the Chaîne des Puy , there are about 9500 years. This impact is dramatically changing the vision of volcanologists on these trachytic eruptions in connection with prehistoric human activity.

 

Sources :

- Eruptions trachytiques de la Chaîne des Puys (France) et leurs impacts sur les environnements - par Gérard Vernet et Jean-Paul Raynal - link

- La Formation de Marsat et le Téphra CF7, marqueurs distaux d’éruptions trachytiques violentes de la chaîne des Puys au Boréal - par Vernet et Raynal - link

Nouvelles données sur le téphra de Sarliève et le téphra CF7, marqueurs chrono-stratigraphiques de Grande Limagne (Massif central, France) D. Miallier et al., C. R. Geoscience 336 (2004).

- Guide des volcans d'Europe et des Canaries - M.Krafft & de Larouzière - éd. Delachaux & Niestlé

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

The 38th World Heritage Committee will decide soon on the registration of the Chaîne des Puys and the Limagne fault (Massif central / France) of 15 to 25 June 2014 folder.

In this context, where the Limagne is associated , research for 25 years at the foot of the volcanic area of Chaîne des Puys helped to identify four pyroclastic formations attributed to acid magma volcanoes .

The Marsat formation , identified in 1995, covers two prehistoric archaeological levels . It is related to the eruption of Puy Chopine , dated there 9479 (+ / - 49 ) years.

Massif Central - Puy des Gouttes and Puy Chopine - aerial photos paramotor / Puy de Dome, courtesy of Damien Bouyssi

Massif Central - Puy des Gouttes and Puy Chopine - aerial photos paramotor / Puy de Dome, courtesy of Damien Bouyssi

The Puy des Gouttes and the Puy Chopine are associated morphologically and historically


Puy des Gouttes gets its name from the Latin gutta , meaning source ... exceptional in the Chaîne des Puys , this volcano had two sources. One located in the iron-horse, embracing the puy Chopine has long fueled a pond, called Choupina . The other to the outside Lemptéguy , was captured in the 18th century by the Benedictines of St Alyre to fuel "Fountain of the Fathers ." These sources emerge in favor of a fault line on which eight volcanoes, from Lemptéguy to Raviole . The Puy des Gouttes - 1.134 m - in the shape of a crescent open to the north , is a cinder cone with outer gentle slopes and barrancos , radial ravines and steep inner slopes. It is dated to 30,000 years and lapilli covered a large area , among which are bombs crust . A black trachybasalt flow with olivine and pyroxene phenocrysts is effused towards the west and the village of Fontêtes .

The trachytic crater of explosion of Puy Chopine notch the Puy des Gouttes .

Puy Chopine - 1.181 m - . Forming a large pyramid of trachyte , 600 m. basal diameter and 150 m. height , dominating the puy Drops of about 50 meters. Puy Chopine consists of gray trachyte with feldspar , pyroxene and black mica , but also signs of the crystalline basement - granite, diorite , corneal - who is now 200 m. above their usual level and are especially visible on the southern slope of the needle.

Its name may come from the Latin campus , referring to farmland extending at his foot and gives Campina in 1313 . Another source comes from the Gallic Suppe or Supia designating a wetland, or a lake reported in the literature between the two wells , but now its gone ... the local pronunciation gave choupina .

Puy Chopine , seen from puy des Gouttes - photo Fcarcena .

Puy Chopine , seen from puy des Gouttes - photo Fcarcena .

 Evolution of the Gouttes-Chopine system - doc . Parc des Volcans publ . 8 / Guide volcanoes in Europe.

Evolution of the Gouttes-Chopine system - doc . Parc des Volcans publ . 8 / Guide volcanoes in Europe.

The history of the Gouttes-Chopine is written in two periods:

- There 30,000 years , a fissure eruption lets out a trachybasaltic casting , which flows westward and then, a series of explosions will form the cinder cone of Puy des Gouttes.

- There are about 9,500 years , an explosion crater opens and forms a trachytic maar 600 m. diameter , leaving only the southern part of Puy des Gouttes in crescent and a flap in the north. This will generate phreatomagmatic trachytic clouds which will cover more than 20 km ² ... the Gouttes cone is buried under deposits of clouds which descend to share its outer flanks and will dig gullies that give the characteristic appearance. At the end of the eruptive cycle , granitic basement panels slide into the crater. Degassed magma will rise like a piston in the chemney, pushing back the products that clog to build the needle of Puy Chopine ( in a similar pattern to the needle of Mount Pelee ) . The main slab of granite is 150 m. long, 100 m. wide and high ... imagine the force to lift the mass . A fumerolienne activity will close the eruptive cycle.

The Puy Chopine notching the puy des Gouttes - Winter picture / aerial photos paramotor / Puy de Dome, courtesy of Damien Bouyssi .

The Puy Chopine notching the puy des Gouttes - Winter picture / aerial photos paramotor / Puy de Dome, courtesy of Damien Bouyssi .

The history of the "man of Marsat" :

at the edge of the Mirabel strem in the Limagne fault, a hunter-gatherer camp is held in the spring / early summer.

After a rain of ashes, despite the distance, due to the collapse of the eruptive column in the Pelean phase of the eruption of Puy Chopine, a mudslide will invade the camp. The water accumulated in various dams will take rocky debris, blocks of trachyte, mixed with tree trunks, forming a destructive lahar. After the lahar, the valley is covered by a thin layer of trachyte ash.

This is the first time we watch that a Mesolithic hunting camp was a direct witness an eruption of the volcanos, though placed at considerable distance - more than 11 km - from the eruptive source.

Sources :

- Eruptions trachytiques de la Chaîne des Puys (France) et leurs impacts sur les environnements - par Gérard Vernet et Jean-Paul Raynal - link

- Domenicus malleotus - le Puy Chopine - link

- Volcan Terre d'éveil - link

- Guide des volcans d'Europe et des Canaries - M.Krafft & de Larouzière - éd. Delachaux & Niestlé

- Chaîne des Puys - le Puy Chopine - l'aiguille de protusion par B.Dichamp - link

- Les photos aériennes du Puy de Dôme - merci à Damien Bouyssi pour son autorisation de diffusion -   link

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
Yap / Micronesia - photo Conservation Strategy Fund

Yap / Micronesia - photo Conservation Strategy Fund

The state of Yap consists of four major islands , Yap , Maap , Tomil, Rumong, seven small islands and 134 atolls. They are of volcanic origin and composed of volcanic and metamorphosed ultramafic rocks , coral and mangrove mud .

Yap islands are a volcanic arc system to the eastern edge
of the Philippine oceanic plate (Yao trench) and are connected to the arc of Palau to the south, and the Izu- Mariana arc to the north. Yap is located on the edge of the microplate Carolina , subducting beneath the Philippine plate.

Volcanism ended in Yap arc at the end of the Oligocene or Miocene , with no evidence of activity then .

Tectonics Caroline Islands - doc . Geological origin of the volcanic islands of the Caroline

Tectonics Caroline Islands - doc . Geological origin of the volcanic islands of the Caroline

Yap - stone money - photo Experiencemicronesia

Yap - stone money - photo Experiencemicronesia

This is not the only feature of Yap !

She is also known for its currency : large disks usually made of calcite , cut in a doughnut form (with central hole ) , ranging from 3.5 cm. up to 4 meters in diameter. Five major types coexist : the Mmbul , Gaw , Fe ' or Rai , Yar , and Reng . Many discs comes from other islands, as far away as New Guinea , but the majority comes from Palau .

Discs of Yap looks like quartz, and historically, their value was related to their specific brillance. Apart the beauty of the rock and the story relates to the stone itself ( age , number of victims for its extraction, and his transport) , its size is also taken into account to determine the value , as well as the social status of the parties to the transaction.
As no more disc is imported or produced , the exchange remains fixed.

Today, the currency used for transactions is the U.S. dollar, and the stone discs are used for traditional or ceremonial exchange . The stones do not move, but can change ownership during marriages , transfers of title, or as compensation for damages.

Yap - transporting the stone money - photo Francis X. Hezel

Yap - transporting the stone money - photo Francis X. Hezel

Yap was populated by migrants from the Malay Peninsula , Indonesia , New Guinea and the Solomon Islands . By cons , the outer islands were by Polynesians . Historically , a tributary system existed between Yap proper and the outer islands ... in relation to the need to get goods from the Big Island , as food or wood to build boats.

The people of Yap in Micronesia is known for its traditional dances performed during festivals and special occasions like marriage of a chief. Dance of Yap, called Churu ' is transmitted from generation to generation carefully , together with historical songs . The dancers dress in leaves and flowers of coconut and coat the skin of turmeric and coconut oil to give them a golden appearance . These dances are performed in separate male or female groups. Other dances originating from the outer islands , such as the war dance highlighting the art of fighting with sticks , are performed by mixed groups of young people .

Yap - dancers dressed for the ceremony - photo Yap Day

Yap - dancers dressed for the ceremony - photo Yap Day

Sources :

- Geological origine of the volcanic islands of the Caroline - link

- Federated states of Micronesia - traditional culture - link

- Musée de la Banque Nationale de Belgique - la pierre de Yap - link

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