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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 Icelandic weekend to see the eclipse was also an opportunity to glimpse the volcanism of the south coast of the island.

Emerging from Keflavik airport, the Reykjanes peninsula offers a first contact. The volcanic system Reykjanes, southwest of the peninsula of the same name, is an extension in surface of the Mid-Atlantic Ridge, includes a wide range of eruptive fissures system, craters and postglacial small basaltic shields.


 

Lavas in the Reykjanes peninsula / Grindavik - photo © 2015 Bernard Duyck

Lavas in the Reykjanes peninsula / Grindavik - photo © 2015 Bernard Duyck

Lavas in the Reykjanes peninsula / Grindavik - photo © 2015 Bernard Duyck

Lavas in the Reykjanes peninsula / Grindavik - photo © 2015 Bernard Duyck

The greater part of the Reykjanes volcanic system is covered with lava emitted during the Holocene. Subaerial eruptions are indicated in the course of the 13th century on a group of cracks aligned NE-SW, as many underwater eruptions in the 12th century, some of which have formed ephemeral islands.

 

Volcanic centers and high temperature geothermal areas - Doc. Icelandic geosurvey

Volcanic centers and high temperature geothermal areas - Doc. Icelandic geosurvey

Volcanic and geothermal areas on parallel cracks in the Reykjanes peninsula - Local indicative sign - photo © 2015 Bernard Duyck

Volcanic and geothermal areas on parallel cracks in the Reykjanes peninsula - Local indicative sign - photo © 2015 Bernard Duyck

Gunnuhver / Grindavik is the geothermal area further west, as close as the boundary between the North American and Eurasian tectonic plates. Infiltration waters probably mixed with sea water are heated by magma, and the steam that emanates reached more than 300 ° C, making it one of the geothermal areas among the warmest on Reykjanes.

Reykjanes is subject to significant seismic activity, characterized by low magnitude swarms. Some of them have caused a slip at a crack through Gunnuhver; these ground motions have revitalized the intermittent steam field and allowed an outlet to the deep water reservoir in the form of geysers. The 1918 earthquake had formed a powerful geyser with a bubble of 5 meters, named "Hverinn 1918". Reactivated in September 1967 by an earthquake, he erupting with a throw over 12 meters high. A geothermal rilling ended its existence in 1983.

The waters acidified by gases, primarily carbon dioxide and hydrogen sulfide, altered volcanic rocks to turn today into mud pots.

The vapors from the soil have given their importance increased after the start of the industrial exploitation in 2006. From 2008 to 2010, the area was partially closed by the Civil Defense because of the danger of eruption, and destruction of the boardwalks.

 

Gunnhuver / Grindavik : hot springs and fumaroles - photo © 2015 Bernard Duyck

Gunnhuver / Grindavik : hot springs and fumaroles - photo © 2015 Bernard Duyck

Grindavik - geothermal installations - photo © 2015 Bernard Duyck
Grindavik - geothermal installations - photo © 2015 Bernard Duyck

Grindavik - geothermal installations - photo © 2015 Bernard Duyck

Gunnhuver - bridge destroyed by the activity at the beginning of the decade - photo Iceland islandsmyndir.is / Rafn Sigurbjörnsson

Gunnhuver - bridge destroyed by the activity at the beginning of the decade - photo Iceland islandsmyndir.is / Rafn Sigurbjörnsson

The name Gunnhuver derives from that of a ghost, Guðrún Önundardóttir, nicknamed "Gunna". According to a common legends about this, she was a farmer near Kirjubol, a property owned by a lawyer, Vilhjalmur Jonsson. When Gunna did not honor the payment of the rent, Vilhjalmur took away his only possession, a cooking pot. Gunna became furious and refused to drink holy water and fell dead. On the way to the cemetery, holders of the coffin noted that it was becoming strangely lighter. And when the grave was dug, people heard; "No need to dig deep, no plans long  to lie"  ... it was obviously Gunna speaking, now a hate spectrum ! The next night, the body of Vilhjalmur was found on the moor, blue and with broken bones ... the revenge of Gunna.

Another story tells that a priest named Eirikr felt capable of exorcism, and finally threw Gunna a geyser, which took his name. According to the tales of the time, you should be able to see her refusing to let it grow.

Reykjanesvitti - photo © 2015 Bernard Duyck

Reykjanesvitti - photo © 2015 Bernard Duyck

The geothermal area is close to the Reykjanes lighthouse, in Icelandic Reykjanesvitti, the oldest lighthouse in Iceland.

The octagonal original structure dates from 1878; the lighthouse was destroyed eight years after its construction by an earthquake. In 1929, the new lighthouse, in the traditional look but in concrete this time, was equipped with modern lighting, emitting a flash every 30 seconds. The focal plane is 73 meters above the level of the sea.

To follow, the volcanic system Krísuvík

 

Sources:

- Global Volcanism Program - Reykjanes

- Icelandic geosurvey - link

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

A total solar eclipse is a rare phenomenon to be observed ... 71 total eclipses occurred in the 20th century in the world. The 21st century will see 68 eclipses, and it is the 9th of this century. The shadow of the moon is projected this time on a tape that goes from the southern Greenland to the north pole, by the Faroe Islands and Svalbard. Partial Phase interested Icelandic coast in its southern portion, near the northern limit of this band.
 

 Visibility zone of the eclipse - Doc. IMCCE / Paris Observatory / P.Rocher

Visibility zone of the eclipse - Doc. IMCCE / Paris Observatory / P.Rocher

 Visibility zone of the eclipse / time of the greater eclipse - Doc. Great American eclipse

Visibility zone of the eclipse / time of the greater eclipse - Doc. Great American eclipse

I had the opportunity to see her in Vík í Mýrdal (in Icelandic : " the Bay (Vik) of the valley (dal [ur]) of swamp (MYR [i]) " or more commonly Vik) on the south coast Iceland, on March 20, 2015, where she was seen more than 95%.

The viewpoint is located on the site of Dyrhólaey, a peninsula formed partially by a submarine eruption 80,000 years ago, and made of tuff to the east and to the west of dolerite.

Considered as one of the top ten beaches in the world, it houses various rocky headlands, Litlidrangur, Kambur (height 29 m), Mávadrangur (32 m), Lundadrangur (34 m), Háidrangur (43 m), Söðulsker, Stampur, Miðsker, Skershali.

 Vik - Dyrhólaey: the observation site of the eclipse - photo © 2015 Bernard Duyck

Vik - Dyrhólaey: the observation site of the eclipse - photo © 2015 Bernard Duyck

 The eclipse in climbing max. phase - Photo © Jean-Michel Mestdagh 2015

The eclipse in climbing max. phase - Photo © Jean-Michel Mestdagh 2015

 The eclipse in downturn - photo © Jean-Michel Mestdagh 2015

The eclipse in downturn - photo © Jean-Michel Mestdagh 2015

The eclipse of March 20 seen to Vik, Iceland.
 Vik - Dyrhólaey: ambiance at the time of the eclipse - photo © 2015 Bernard Duyck

Vik - Dyrhólaey: ambiance at the time of the eclipse - photo © 2015 Bernard Duyck

Eclipses are related to the history and legends ...

The Aztecs attributed the eclipses to the fight between Quetzalcoatl, the feathered serpent, and Tonatiuh, the sun god. Among the Egyptians, the legend connected them to attack of the sun god Ra by the snake Apophis.

In Scandinavia, two giant wolves Sköll ('push') and Haiti ("Hate"), which chase the sun and the moon, and eventually devour them.
An Icelandic legend is related to site of Reynisdrangar, near Dyrhólaey :  two trolls have been surprised by the first rays of the sun while trying to thwart a three-masted on the shore and turned to stone ... these are the needles of lava eroded by the sea and the wind ... but that's another story, to be followed in a few days.
 


Sources:
Thanks to my friend Jean-Michel for his shots during the eclipse.
The various sites
- cited: IMCCE / Paris Observatory and Great American Eclipse
- or consulted in advance: Nasa - Astrosurf - INPES

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
Sinabung / Sumatra continuous activity and formation of a new lobe.

The head of the Sinabung observation station, Armen Putra, said in an interview with Jakarta Post that volcanic activity remains high and that future eruptions are expected.
He said that the events of March 5 are the most important in 15 days.

Pyroclastic flows have expanded to 4.5 km south of the volcano.
A forested area along the river Borus Lau, in the village of Berastapu, was destroyed by a pyroclastic flow.

Mt Sinabung Observation Station head Armen Putra
Mt Sinabung Observation Station head Armen Putra
Sinabung - lahar on Lau Borus river - photos endrolew@ 05.03.2015
Sinabung - lahar on Lau Borus river - photos endrolew@ 05.03.2015

Sinabung - lahar on Lau Borus river - photos endrolew@ 05.03.2015

Three districts located on the west of the volcano, Tiganderket, Payung and Kutabuluh were covered with ashes.
A flight to Singapore was canceled at the international airport in Deli Serdang

2015.03.06 Sinabung after the big erupsion in Thursday March 5. taken from Sebintun corn field. - Sadrah ps

2015.03.06 Sinabung after the big erupsion in Thursday March 5. taken from Sebintun corn field. - Sadrah ps

Observations show that a new dome quickly reforms, with some early rock falls and nighttime glow.

Sinabung - the new lava lobe on 06.03.2015 / 13h29 - photo Sadrah ps / Twitter

Sinabung - the new lava lobe on 06.03.2015 / 13h29 - photo Sadrah ps / Twitter

Sinabung - early rock falls and nighttime glow - photo endrolew@ 06.03.2015 / 21h51

Sinabung - early rock falls and nighttime glow - photo endrolew@ 06.03.2015 / 21h51

Sources :

- Jakarta Post - Mt Sinabung eruptions trigger forest fire, disrupt flight

- Photos via Twitter et Facebook / Mabah Lëwa & Sadrah Peranginangin.

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

This volcanic plateau, carved out by glaciers, is crossed by an old Roman road, from Germany and Switzerland to Spain.

In villages that dot this immensity, Nasbinals, Marchastel, Saint-Chely-d'Aubrac or Laguiole, say scary legends of lost travelers, "died of cold" or murdered by bandits or the "Beast of Gevaudan."

 

Aubrac - the Pilgrim from Nasbinal to Conques - photo Pedestria

Aubrac - the Pilgrim from Nasbinal to Conques - photo Pedestria

The ghost of the dead pilgrims on Aubrac:

The foundation of the Order of Aubrac hospital in 1120 by a noble Compostela pilgrim named Adalard Eyne, viscount of Flanders, is the subject of stories, two centuries later.

Returning from his pilgrimage with his troop of thirty knights, he crosses the Aubrac at dusk. The troop seek shelter for the night and set his heart on a cave ... they find twenty murdered travelers heads, probably also the pilgrims. Christ appeared and asked Adalard to found a hospital in this dangerous place. Adalard ended his pilgrimage and returned to base it.
 

The "Domerie d' Aubrac" - Doc. Archive

The "Domerie d' Aubrac" - Doc. Archive

Another version of the legend is shown in a tapestry of the 17th century stretched in the church: Adalard would have made his vow starting to Compostela, but had forgotten. Back through Aubrac in return he was rebuked by Christ, who brought down his mule in the snow.

A third version of 19 century: Adalard attacked by bandits on the way, vowed if he escaped them, to found an asylum here to receive and escort the pilgrims ... that he will when he return : He built a hospital, run by priests, brothers and sisters, and guarded by twelve knights to escort pilgrims. He remained there until the end of his days.

For those who want to judge the historical truth, I refer you to the site:
Saint Jacques / Aubrac
 

The "Domerie d'Aubrac" today - photo www.chemin-st-guilhem.fr

The "Domerie d'Aubrac" today - photo www.chemin-st-guilhem.fr

The "Beast of Gevaudan"

The Beast of Gevaudan is an animal
source ofa series of attacks against humans occurred between 30 June 1764 and 19 June 1767. These attacks, often fatal, among a hundred, took place mainly in the north of the former country of Gevaudan (which generally corresponds to the current department of Lozere), a breeding area.
 

"Figure of the Monster that saddens Gevaudan" engraving on copper 1764/1765 (Wikipedia / gallica)

"Figure of the Monster that saddens Gevaudan" engraving on copper 1764/1765 (Wikipedia / gallica)

The "Beast of Gevaudan" quickly passed from the stage of the news story, to the point of mobilizing many royal troops and give rise to all sorts of rumors, both the nature of this "beast" - in turn seen as a wolf, an exotic pet and even a werewolf ... or a serial killer in more recent times, as the reasons which drove to address populations - the divine punishment to the theory of the trained animal to kill.

Among the many animals slaughtered during this period, two canines are believed to be the Beast. The first is a great wolf killed by François Antoine, arquebuse holder of the King of France, on the field of the royal abbey of Chazes in September 1765. Once the wolf stuffed in Versailles, the newspapers and the Court lost interest in this case, although other deaths were deplored later. Jean Chastel, farmer from La Besseyre-Saint-Mary, killed the second beast, identified as a wolf or large dog in June 1767. According to the tradition, the animal killed by Chastel, was well the Beast of Gevaudan, past this date, no fatal attack was not reported in the province. (From Wikipedia)

 

Gevaudan wolf ... not the "beast", but a magnfique Wolf seen in the "Gevaudan's Wildlife park of Wolves" - photo Altitude Rando

Gevaudan wolf ... not the "beast", but a magnfique Wolf seen in the "Gevaudan's Wildlife park of Wolves" - photo Altitude Rando

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
The cascade of Déroc / Aubrac - she dives off a basalt flow - Photo Altitude Hiking / courtesy of its author befakali.

The cascade of Déroc / Aubrac - she dives off a basalt flow - Photo Altitude Hiking / courtesy of its author befakali.

Second  part of areas where the volcanism is revealed in Aubrac :  the waterfall of Déroc,the creek of Plèches, and the waterfall of Saltou

The waterfall and the shelter of Déroc:

In the commune of Nasbinals, the waterfall of Déroc dominates the small glacial valley of Gambaïse. The waters of the glacial Lake Salhiens sheer drop of 33 meters from the edge of a cliff consisting of a basalt flow.

Surprising landscape on the Aubrac plateau, but the highlight of the show is under the waterfall: it houses a rock ceiling shelter made of dark basalt prisms.

Discovered by Dr. Prunière, this "cave" was used, according to legend, as a refuge for bandits and cutthroats that prevailed on the old Roman roads and roads used by the pilgrims of Saint Jacques de Compostela.

 

Waterfall of Déroc - the ceiling of the rock shelter unveils beautiful of basalt - Photo Altitude Rando

Waterfall of Déroc - the ceiling of the rock shelter unveils beautiful of basalt - Photo Altitude Rando

Waterfall of Déroc - Erosion continues his work and large pieces of organs littering the floor of the shelter - visitors for scale - photo Terres & Civilizations

Waterfall of Déroc - Erosion continues his work and large pieces of organs littering the floor of the shelter - visitors for scale - photo Terres & Civilizations

To reach the cave, you must go down on wet and slippery blocks from the cliff ... that is not secure! Caution is advised.

For directions, see the website Altitude Rando / Lake Salhiens and waterfall of Déroc -
link

Basalt columns of the "Bridge of Negroes" - photo Altitude Rando

Basalt columns of the "Bridge of Negroes" - photo Altitude Rando

The prismated flow of the creek of Plèches :

Southeast of Nasbinals, downstream from the bridge of the Negroes, a basalt columnar jointing casting is visible in the bed of the stream of Fisheries.

Although eroded the columns are in the form of a "causway".

"The Plèches creek" to the "Bridge of Negroes" - photo lozerepeche.

"The Plèches creek" to the "Bridge of Negroes" - photo lozerepeche.

 Waterfall of Saltou - photo Randozone

Waterfall of Saltou - photo Randozone

Sources :

- Altitude Rando - Lac des Salhiens (1211m) et cascade du Déroc (1208m) - Monts d’Aubrac - link

- BRGM – L’Aubrac - link

- Parc Naturel régional de l'Aubrac - link

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
Landscape of Aubrac plateau - Doc. Natural Park of Aubrac

Landscape of Aubrac plateau - Doc. Natural Park of Aubrac

The issuance of FR3, "Roots and Wings" last week made us travel the Lot river, from the Garonne River to its source on the Mont Lozère, along the basaltic Aubrac plateau.

Aubrac takes its name from "Alto Braco" meaning an high, humid place, the second element "brac" may be derived from either the Gallo-roman meaning "damp, muddy" , in Old Occitan brac = mud.

Aubrac, located in the French Massif Central, is a vast basalt plateau lying NW-SE on 450 km². The thickness of the volcanic ranges from less than 100 meters on the peripheral fringe, to 300 meters below the summit, where the lava flows overlap.

According to the most recent analyzes (Goer de Herve A. & al. 1991-1993), 90% of Aubrac's lava  would have been issued on a very short time, in the order of 250,000 years between there are 8,7 million years and 6 Ma. (upper Tortonian)

The lavas of Aubrac are a poorly differentiated recurring series, silica content of 42-52% and are divided into nine chemical classes: picrites, basanites, alkali basalts and subalcalins, hawaiites and trachybasalts, mugearites, tephrites, phonotéphrites. Lavas have been issued in an effusive way in many points distributed on the plateau, before being heavily eroded by glaciers that have left lakes and bogs. (BRGM)

 

Volcanic provinces of the French Massif Central - 7 / Aubrac - map after Nehlig P. & H. Sledge / in aurelienb.

Volcanic provinces of the French Massif Central - 7 / Aubrac - map after Nehlig P. & H. Sledge / in aurelienb.

Age of volcanic sets of the French Massif Central - doc.BRGM

Age of volcanic sets of the French Massif Central - doc.BRGM

 3D map of Aubrac plateau - © Agreement Lot Valley

3D map of Aubrac plateau - © Agreement Lot Valley

The plateau consists of various rocks, granite in the north and east, gneiss, schist in the foothills, and basalt in the center, and he lets see witnesses of the volcanic activity in various sites and in various forms: a Neck to Belvezet, a dyke at Alcorn, basalt columns at the waterfall of Déroc, in the stream of Plèches and the waterfall of Saltou.
 

The neck of Belvezet - photo montsdaubrac.uniterre

The neck of Belvezet - photo montsdaubrac.uniterre

The neck of Belvezet dominates the hamlet - photo www.xn--saint-chly-daubrac-iwb.fr

The neck of Belvezet dominates the hamlet - photo www.xn--saint-chly-daubrac-iwb.fr

The neck of Belvezet:

Located halfway between the villages of Aubrac and Saint-Chely, on the way to Saint Jacques de Compostela, this hamlet is nestled at the foot of the ruins of a tower, built on the neck, an old lava chimney clearing by erosion. Volcanic rock is found all around this small village.

 

Le Truc des Coucuts to Prinsuéjois - photo Académia

Le Truc des Coucuts to Prinsuéjois - photo Académia

Le Truc des Coucuts :

Le Truc des Coucuts, which rises to 1,280 meters (not accessible) is a basaltic rock with beautiful organ, located on the village of Prinsuéjois. This ancient village has the etymology "the village in the clearing," and present traces of Gallic habitation, and Roman occupation.

This inhospitable region, den of thieves, has been cleared by the monks of the Aubarc Hospital to remove resources for the poorest.
Prisuéjois now lives from agriculture and livestock breeding.

To be continued

 

Sources :

- BRGM – L’Aubrac - link

- Parc Naturel régional de l'Aubrac - link

- Le point sur le risque volcanique en Auvergne  - link

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
The Laacher See: a lake fills the explosion crater, the maar, of the Laacher See volcano - photo Bernard Duyck

The Laacher See: a lake fills the explosion crater, the maar, of the Laacher See volcano - photo Bernard Duyck

The Laacher See differently ... a getaway among the Celts and Romans.

The eruption of the Laacher See not only disrupted the region there are approximately 13,000 years, it has also left an impressive amount of tuff and pumice.

These resources have been exploited since Roman times, here is some 2,000 years. The largest tuff mine north of the Alps, also known as the Meurin career, is located in Kretz / Eifel .


 

Römerbergwerk / Meurin - photo Hochgeladen von Schängel

Römerbergwerk / Meurin - photo Hochgeladen von Schängel

Römerbergwerk in Meurin - left, traces of peaks from the Roman era in the tuff - photo grenswetenschap.nl - to right, a block of tufa - photo FlickrRömerbergwerk in Meurin - left, traces of peaks from the Roman era in the tuff - photo grenswetenschap.nl - to right, a block of tufa - photo Flickr

Römerbergwerk in Meurin - left, traces of peaks from the Roman era in the tuff - photo grenswetenschap.nl - to right, a block of tufa - photo Flickr

The volcanic tuff was operated in dusty and dark galleries, before being brought to the surface. futuristic museum allows to visit the galleries and wells, immaculately protected.

The old mining techniques, and the life of Roman legionaries and minors are enhanced by modern tools of museology in an Archéosite.

 

Römerbergwerk in Meurin - Crane used to raise the blocks of tufa - Doc. Vulkanpark Eifel

Römerbergwerk in Meurin - Crane used to raise the blocks of tufa - Doc. Vulkanpark Eifel

What was the menu offered to the workers?

The meals consisted mostly of bread, decorated with fruits, vegetables, soup beans, cheese ... the "Moretum" consisted of fresh cheese and herbs, pine nuts and / or hazelnuts. The grain allocated to them, barley, spelled and wheat was crushed in a mortar or ground to flour in a mill, and then baked, which also heated the house.

Römerbergwerk in Meurin - Reconstitution of a kitchen of Roman times, with his mortar and flour mill - photos Vulkanpark Eifel
Römerbergwerk in Meurin - Reconstitution of a kitchen of Roman times, with his mortar and flour mill - photos Vulkanpark Eifel

Römerbergwerk in Meurin - Reconstitution of a kitchen of Roman times, with his mortar and flour mill - photos Vulkanpark Eifel

 Nickenich / Eifel - Roman Tumulus - photo Vulkanpark Eifel

Nickenich / Eifel - Roman Tumulus - photo Vulkanpark Eifel

The Romans invaded this land, inhabited by the Celts in the first century AD. To Nickenich, original Celtic name, a "tumulus" built of tufa, a Roman tomb rotunda-like documents the occupation of the city, then called Nigidiacum and its romanization.

In the fifth century AD, the Romans were removed by the Germanic tribe of the Franconian, which became the new settlers of the country.

Sources :

- Vulkanpark Eifel - link

- Zu gast rund um den Laacher See - link

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

North of the Columbia River, the Washington State has five active volcanoes, all part of the volcanic chain of the Cascades :  Mount Adams, St. Helens, Rainier, Baker and the most remote and least known of them, Glacier Peak.
 

North of the Columbia River, other volcanoes ...
Volcanoes in the Cascade Range and tectonics - a click to enlarge - Doc. USGSVolcanoes in the Cascade Range and tectonics - a click to enlarge - Doc. USGS

Volcanoes in the Cascade Range and tectonics - a click to enlarge - Doc. USGS

Resembling to the silhouette of Mt St. Helens prior to its "decapitation", he rises to 3213 meters and dominates the Glacier Peak Wilderness Area, forested. The volcano measure in reality only a little less than 1,000 meters, because it is built on a high ridge.

Twelve glaciers descend on its flanks, which earned him the name ... and obscuring its status of dacito-andesitic stratovolcano, even in the 1850's when native of northwest revealed to
the naturalist George Gibbs that "another small peak north of Mt. Rainier had issued smoke ".

Yet since the end of the most recent ice age, the volcano produced with the St Helens, the most explosive eruptions in this part of the North American continent, in at least six separate volcanic episodes.

 Glacier Peak, head in the clouds - photo Steph Abbeg / Summitpost

Glacier Peak, head in the clouds - photo Steph Abbeg / Summitpost

The summit of Glacier Peak and its shadow - photo John Schurlock / USGS

The summit of Glacier Peak and its shadow - photo John Schurlock / USGS

The volcanism of Glacier Peak, like other volcanoes in the Cascade arc, is due to the subduction of the Juan de Fuca plate beneath the North American plate.

The age of the Glacier Peak volcanic cone is uncertain ... It produces large explosive eruptions that covered the surrounding areas with
tephra deposits; they are accompanied by growth of lava domes, and pyroclastic flows and lahars in the direction of low areas near the volcano.

Primitive eruptive deposits have indeed been eroded by the last glaciation and buried by younger domes, aligned roughly north-south across the top of the volcano. The oldest lava flows, known to be issued from the north and east of the volcano, have been dated between 200,000 and 600,000 years ago.


Upstairs, eruptive history of Glacier Peak last 15,000 years - bottom map of areas at risk of debris avalanches and lahars (mainly in the west drainage) - Doc. USGS

Upstairs, eruptive history of Glacier Peak last 15,000 years - bottom, map of areas at risk of debris avalanches and lahars (mainly in the west drainage) - Doc. USGS
Upstairs, eruptive history of Glacier Peak last 15,000 years - bottom, map of areas at risk of debris avalanches and lahars (mainly in the west drainage) - Doc. USGS

Upstairs, eruptive history of Glacier Peak last 15,000 years - bottom, map of areas at risk of debris avalanches and lahars (mainly in the west drainage) - Doc. USGS

Glacier Peak north side - the exposed rocks are lava flows of the Pleistocene confined between the glaciers - photo Heither Bleick / USGS

Glacier Peak north side - the exposed rocks are lava flows of the Pleistocene confined between the glaciers - photo Heither Bleick / USGS

The top part of Glacier Peak can be divided into three parts, two false summits and the current summit, which is partially covered by the upper parts of  Chocolate glacier, which  leaves exposed to the west and south of a thick flow, high of fifty meters, a remnant of an eruption dome dated there 5500 years.

Further north, a small plateau containing the remains of a recent lava dome. A small dacitic lava flow extends from the center of the false summit to the top of Dusty Glacier, on the NE flank of Glacier Peak.

South of the present summit, Disappointment Peak, the dacite dome-casting, extends over 800 meters on the south-west / south side of the volcano. Its color varies from light gray to pink, and red; its high vesicularity and the presence of red-black prismatic phenocrysts of oxyhornblende distinguishes the dacite of Disappointment Peak from the other dacites of Glacier Peak.

 

Glacier Peak - end of a columnar jointing lava flows, blocked by ice - photo Heither Bleick / USGS

Glacier Peak - end of a columnar jointing lava flows, blocked by ice - photo Heither Bleick / USGS

Disappointment Peak, seen from the climb to Glacier Peak - photo Summitpost

Disappointment Peak, seen from the climb to Glacier Peak - photo Summitpost

 From bottom to top, glacial deposits - at the walking stick, the orange layer of ash from the eruption of Mazama (7,700 years ago) - at the top, the tephra eruptions of Glacier Peak (<7,000 years) formed by co-ignimbritic deposits from repeated  pyroclastic flows - Photo Heather Bleick / USGS

From bottom to top, glacial deposits - at the walking stick, the orange layer of ash from the eruption of Mazama (7,700 years ago) - at the top, the tephra eruptions of Glacier Peak (<7,000 years) formed by co-ignimbritic deposits from repeated pyroclastic flows - Photo Heather Bleick / USGS

North-east side of Glacier Peak - Stratified deposits of pyroclatic flows and lahars, from the collapse of a dome, dated between there 5500-5100 years - Beige rocks in the foreground are deposits altered hydrothermally of the Gamma Ridge formation, filling a small caldera that preceded the modern Glacier Peak - photo Tyson Berndt / USGS

North-east side of Glacier Peak - Stratified deposits of pyroclatic flows and lahars, from the collapse of a dome, dated between there 5500-5100 years - Beige rocks in the foreground are deposits altered hydrothermally of the Gamma Ridge formation, filling a small caldera that preceded the modern Glacier Peak - photo Tyson Berndt / USGS

Sources :

- Cascades Volcano Observatory - Glacier Peak

- Global Volcanism Program - Glacier Peak

- Geological survey – Intrusion and eruption of late Cenzoic magmas in the Glacier peak area, North Cascades, Washington -  Late episode of volcanism : Glacier peak volcano and associated rocks.

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

Near the Columbia River and Portland, a massive stratovolcano consists of several andesitic to dacitic domes, Mount Hood, is an ever present threat to the well region.

These domes were produced during eruptions in the last 730,000 years, based on an ancient volcano this for millions of years.
 

The Mt. Hood dominates the city of Portland - photo Ed Rudlledge / USGS

The Mt. Hood dominates the city of Portland - photo Ed Rudlledge / USGS

Mount Hood is covered with glaciers, and has produced during recent eruptions number of lahars, the latest, not associated with an eruptive activity, reached the Columbia River in 2006.

The volcano has experienced periods of activity of tens or hundreds of years, separated by quiescent periods lasted between hundreds of years and 10,000 years.
Pleistocene collapses produced avalanches and lahars which spread along the Columbia River to the north.

On the left, the glaciers of Mt. Hood - doc from Lidar data / USGS - right risk map - Doc USGS - A click to enlargeOn the left, the glaciers of Mt. Hood - doc from Lidar data / USGS - right risk map - Doc USGS - A click to enlarge

On the left, the glaciers of Mt. Hood - doc from Lidar data / USGS - right risk map - Doc USGS - A click to enlarge

The volcano has experienced at least four major eruptive periods since 15,000 years, including three years since 1800:

 *    Polallie (between 15,000 and 12,000 years) eruptions are contemporaneous or following the Pleistocene glaciation.


 *    Timberline (between 1,800 and 1,400 years)
 *    Zigzag (between 600 and 400 years)
During both this 2 periods, debris avalanches and lahars have borrowed the valleys of the Zigzag River and Sandy River toward the Columbia, installing a delta in the Sandy river, and moving over the Columbia River.

  *   Oldmaid (between 250 and 180 years) pyroclastic flows and lahars, generated by repeated collapses of a lava dome extruded near the current Crater Rock, the remains of the dome, have created deposits distributed between the Sandy River and the White river. Early settlers reported an eruption in 1859 and 1865 to 1866, the official date of the last eruptive activity (in GVP)

 

 Date and description of geological events in the region of Mt. Hood in the past 30,000 years - Doc. USGS

Date and description of geological events in the region of Mt. Hood in the past 30,000 years - Doc. USGS

The delta of the Sandy river, dating from the "Timberline" eruptive period of Mt. Hood - photo Willie Scott / USGS

The delta of the Sandy river, dating from the "Timberline" eruptive period of Mt. Hood - photo Willie Scott / USGS

The southern flank of Mt. Hood, with Crater Rock - photo © Jean-Michel Mestdagh

The southern flank of Mt. Hood, with Crater Rock - photo © Jean-Michel Mestdagh

Near the Timberline Lodge, Crater Rock is a remnant of the dacite dome (hypersthene-hornblende) formed there 2-300 years ago. Her measurements: 300-400 m. at its base and top of 170 m. on its south side; it is surrounded by an area of brecchia of the same composition.

Summit of Mt. Hood, with Crater Rock, less snow covered in the center-left - photo © Jean-Michel Mestdagh

Summit of Mt. Hood, with Crater Rock, less snow covered in the center-left - photo © Jean-Michel Mestdagh

Steaming altered ground of the Mt Hood's summit - James Howles USGS

Steaming altered ground of the Mt Hood's summit - James Howles USGS

A strong fumerolian activity persists today in its surroundings.

The maximum temperature of the fumaroles was measured at 92 ° C, slightly above the boiling point of water at this altitude point at the main geothermal area of the volcano is called "Devil's kitchen" ... this s 'not invented!

 

Sources :

- Global Volcanism Program - Hood

- Cascades Volcano Observatory  / CVO - Mt. Hood

- USGS - Mount Hood - History and hazards of Oregon's most recently active volcano - link

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Publié le par Bernard Duyck
Publié dans : #Excursions et voyages
Columbia river gorge / Oneonta gorge - photo Roadtripper

Columbia river gorge / Oneonta gorge - photo Roadtripper

Along the Columbia river gorge, the various tributaries had to dig the basalt established in the Miocene (between 17 and 12 Ma), to join the river.
This wooded landscape dotted with beautiful waterfalls is accessible via the Historic Columbia River Scenic Byway, a narrow and winding road, long of 113 km. Built in 1913 by Samuel C.Lancaster, it is one of the great engineering contemporary feats ... the scenic beauty has been preserved, its designer "not wanting to ruin what God had created here."

Columbia River gorge - Historic Columbia River Scenic Byway - Unblocked Tunnel in the basalt- photo Pacific northwest photoblog

Columbia River gorge - Historic Columbia River Scenic Byway - Unblocked Tunnel in the basalt- photo Pacific northwest photoblog

Columbia River Gorge - situation of the water falls and Oneonta Gorge

Columbia River Gorge - situation of the water falls and Oneonta Gorge

The highest waterfall in the State of Oregon, Multnomah Falls, viewed from the bottom- Lower Falls and part of Upper Falls / Multnomah Falls. photo David Benbennick

The highest waterfall in the State of Oregon, Multnomah Falls, viewed from the bottom- Lower Falls and part of Upper Falls / Multnomah Falls. photo David Benbennick

The Oneonta Gorge is a striking example. It owes its name to Carleton Eugene Watkins, a native of Oneonta, in the state of New York, who has traveled and photographed for the first time in 1849 during the gold rush.
Not easily accessible, it needs to get wet to get to admire the four major waterfalls that dot the route, Upper Oneonta Falls, Oneonta Middle Falls, Lower Oneonta Falls and Triple Falls, and the basalt walls covered with lichens, ferns and mosses, many of which are endemic to the Columbia gorge.

Oneonta Gorge - Triple falls - photo Oregon wallpapers

Oneonta Gorge - Triple falls - photo Oregon wallpapers

Trails maps in the Oneonta Gorge - a click to enlarge.Trails maps in the Oneonta Gorge - a click to enlarge.

Trails maps in the Oneonta Gorge - a click to enlarge.

Sportive walk to do in the summer, because of the depth of water fed by the melting snow and of his low temperature, she needs to follow the bed of the tributary, with water sometimes up to the chest.

The trail is difficult, due to natural accidents ... we must cross dams formed by tangled trunks of trees or other obstacles ... in the late 90s, the current was partially blocked by three large rocks that have tumbled into the stream. Thereafter a logjam is formed, and created a danger for hikers, which led to a fatal accident in 2011.
If you do not want to soak, there are trails and observation points accessible by land ... but the contact with the basalt will be different.

Oneonta logjam - a comparison between the situation in 1923 and 2011, with the formation of a jam difficult to cross - Doc. Wordpress

Oneonta logjam - a comparison between the situation in 1923 and 2011, with the formation of a jam difficult to cross - Doc. Wordpress

The logjam on Oneonta Gorge - dangerous crossing - photos & Tripadvisor Word of waterfallsThe logjam on Oneonta Gorge - dangerous crossing - photos & Tripadvisor Word of waterfalls

The logjam on Oneonta Gorge - dangerous crossing - photos & Tripadvisor Word of waterfalls

Sources :

- Routes et circuits routiers d’Oregon / Travel Oregon - link

- Pacific northwest photoblog - link

- Wy East blog - Let's clear the logjam at Oneonta Gorge - link

- Black Watch Sasquatch blogspot - Oneonta gorge / Columbia river Gorge - link

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