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#lava

2 posts2 participants0 posts today
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Ð's©🇮🇸

Red is not dead !

Après avoir grimpé la montagne qui jouxte l'Hitarvatn, j'ai trouvé une piste qui relie ce lac à un autre. La route était 50% confortable (terre fine et sèche)/50% chaotique (roches, trous). À mi-chemin, fin du trajet : la piste est encore sous une épaisse couche de neige. Pour avoir roulé sur certains paquets, c'est comme de la boue : tu "pati-niques" et tu te dis que ce sera plus safe en mai.

Seul au monde. Et les paysages sont toujours aussi BEAUX. :hakase:

Vue générale de l'Hitarvatn depuis une petite montagne verte couverte de mousse et de végétations. Des chaînes de montagnes partiellement enneigée entourent l'étendue d'eau. Le ciel est complètement dégagé.
Vue en direction de l'Hitarvatn avec la petite montagne verte qui le jouxte. Au premier plan, le sommet d'un ancien volcan avec de la roche rouge/ocre rouge. À droite du lac, un petit volcan brun et vert. Au fond, des chaînes de montagnes. Dans l'axe de la montagne verte, de l'autre côté de la montagne qui se termine en pointe, il y a un autre grand lac. À gauche, un ancien champ de lave. Si vous zoomez, vous pourrez apercevoir en contrebas mon véhicule.
Même sommet sous un autre angle. Le versant est très rouge et contraste avec le reste : montagne brun-vert, mousse végétale, neige et ciel bleu.
Toujours le même sommet. Secteur ou la piste s'arrête à cause de la neige. Un immense montagnense termine en pointe. Au centre, on devine un petit volcan. L'autre lac se situe vers la droite, de l'autre côté du col entre les deux petites montagnes enneigées.
#iceland#lava#lake
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Ð's©🇮🇸

Je poursuis mon exploration loin des grands axes et globalement, ça me réussit bien. Hier, ce fut l'extase. J'ai découvert par hasard une piste au bout d'une route secondaire (539) dans le secteur de Borgarnes et qui mène à un grand lac : Hitarvatn.

Je pense que c'est la plus belle piste que j'ai empruntée depuis que je vis ici. Les couleurs et les paysages m'ont collé un eyegasm permanent ! :hakase:

Obligé d'y retourner demain ou lundi pour débuter une série de randonnées magnifiques !

Une piste rouge (roche volcanique) traversant un ancien champ de lave. Ce dernier est recouvert d'une mousse végétale vert pâle. Au fond à droite, une petite montagne d'un vert pâle différent : Holmur (364 m alt). À gauche, des rocheuses encore bien enneigées aux sommets. Le ciel est complètement dégagé.
Une petite montagne avec des reflets rouges et ocre jaune : Rauðakula (259malt). L'autre montagne à droite présente un vert un peu terne : Fossabjörg (351m alt). Le paysage aux alentours est désertique avec une teinte majoritairement brun-ocre jaune. 3 petits nuages sur la droite.
Vue d'une partie du lac à la fin de la piste. Les montagnes enneigées au fond au milieu et à droite se reflètent dans les eaux plutôt calmes.
#iceland#roadtrip#lake
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Nicole Sharp

Reclaiming the Land

Lava floods human-made infrastructure on Iceland’s Reykjanes peninsula in this aerial image from photographer Ael Kermarec. Protecting roads and buildings from lava flows is a formidable challenge, but it’s one that researchers are tackling. But the larger and faster the lava flow, the harder infrastructure is to protect. Sometimes our best efforts are simply overwhelmed by nature’s power. (Image credit: A. Kermarec/WNPA; via Colossal)

Aerial view of lava overflowing a road and the surrounding landscape in Iceland.
#fluidDynamics#fluidsAsArt#geophysics
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MediaFaro News Digest

Icelandic fishing village evacuated as lava spews from volcanic eruption.

Iceland's famous Blue Lagoon spa also closed after the Sundhnúksgígar volcano started spouting lava on Tuesday and the village Grindavík was evacuated, apart from eight residents who refused to leave.

mediafaro.org/article/20250401

Le Monde · Icelandic fishing village evacuated as lava spews from volcanic eruption.By Le Monde
#Iceland#Volcano#Lava
Continued thread
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Giuseppe Bilotta

Why does this all matter for #lava flow #modeling? Because most probably lava is non-Newtonian. This means that in our wish to determine how its viscosity depends on the chemical and physical properties of the melt, we're not looking for ONE functional relationship (the viscosity coefficient), but multiple ones: for example, assuming a Herschel–Bulkley model we'd need to find THREE such functional relationship: one for the yield strength, one for the exponent, and one for the coefficient. All of these measured on the actual lava flows across different volcanoes at different times and in completely uncontrolled conditions.

As you can see, not exactly the simplest of tasks.

And of course, if we don't have these functional relationship we can't actually model lava flows.

Or can we?

8/

Continued thread
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Giuseppe Bilotta

So, I mentioned already that we cannot really model #lava flows. The main reasons for that is that we don't actually know how lava behaves, at least not in sufficient detail.

Of course, lava is a fluid, and a (very) viscous one at that, so we know that it follows the Navier–Stokes equations. We also know that its behavior is heavily dependent on temperature, so we know that we also need the heat equation, with both kinds of boundary conditions (conduction to ground, and radiation on the free surface).

And that's all we know. Seriously.

OK, not really, but everything else is extremely uncertain. When modeling a viscous fluid (like lava, or any other geophysical flow for the matter), the first thing you need to know is what the viscosity is. And for lava, we don't know. There's a lot of things we do know, but not enough.
For example, we know that the viscosity depends on temperature, chemical composition, degree of crystalization, amount and types of volatiles in the melt, and so on and so forth. But we don't exactly know the laws relating the viscosity to all of these chemical and physical properties.

2/

#NavierStokes#NavierStokesEquations
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Giuseppe Bilotta

I'm going to take advantage of the current #eruption on Mt #Etna to discuss some of the challenges of #modelling #lava flows. Buckle up (or just silence me) because this is going to be a long thread.

First of all, why do we want to model lava flows? The answer most definitely isn't «because we can», since —as I'm going to explain momentarily— we actually cannot. Still having an idea about how lava flows and sets in place is a powerful tool for the assessment (and possibly mitigation) of the associated #hazard and #risk: if we can tell how lava flows, we can tell which areas are going to be reached by the lava, and hopefully also improve the design of tactical and strategic actions that can be taken to minimize the damage.

(Of course, whether or not those actions will then be taken is an entirely different matter, but that's mostly politics, not science.)

1/

#MtEtna#simulation#CFD
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💧🌏 Greg Cocks

Atop The Oregon Cascades, [Research] Team Finds A Huge Buried Aquifer
--
eurekalert.org/news-releases/1 <-- shared technical article
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doi.org/10.1073/pnas.241515512 <-- shared paper
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usgs.gov/centers/oregon-water- <-- shared USGS technical article, 2011, ‘McKenzie River Source Water Study’
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youtu.be/6R8e5HwGMwU?si=sniW4b <-- shared media video overview
--
#GIS #spatial #mapping #model #modeling #water #hydrology #Oregon #Cascades #CascadeMountains #PNW #PacificNorthwest #volcanic #rocks #aquifer #waterresources #watermanagement #climatechange #snowpack #drought #spatialanalysis #CriticalZone #geohazards #geology #engineeringgeology #landscapes #weathering #bedrock #holocene #groundwater #structuralgeology #orogeny #remotesensing #geophysics #sampling #drilling #porosity #permability #tomography #lava #spring #seep #breccia #discharge #streams #runoff #precipitation #climate #rainfall #recharge

photo - Scientists examine a large-volume spring in young volcanic rocks of the McKenzie River watershed on the west side of the Cascade topographic crest that was monitored as part of this study. Credit: Benjamin Nash
map, photo and charts - (A) Electrical resistivity tomography of Olallie North Spring, which emerges along a flow contact of _25 ka Scott Mountain lava flows. Lateral variations correspond to spring discharge points along the lava flow basal breccia such as depicted in (B) (photo: Benjamin Nash). (C) Mean of total yearly range in discharge _Q divided by mean annual flow Qavg versus average upstream age for springs and streams. The horizontal line defines “spring-” versus “runoff-” dominated. (D) SD of yearly average summer discharge (June–September), normalized by Qavg, with CZ state shift labeled.
maps and chart - (A) Distribution of geothermal drill holes. Thin black circles’ radii scale with total logged length, and colors indicate the fraction of length for which dT=dz < 20_C/km (implying downward flux of meteoric water). Red circles are the fraction with inverted gradients (dT=dz < 0_C/km). The purple contour indicates bedrock ages <2 Ma, while stars mark Holocene age phreatomagmatic eruption vents. (B) Two example temperature-depth logs from deep wells in old and young bedrock. (C) Porosity (blue) and resistivity (orange) in the Santiam Pass drill hole SP 77-24. Dashed lines indicate low porosity at high measured resistivity. (D) Chemical weathering tracked by oxidation state of iron in the Santiam Pass drill hole. The green box indicates range of Quaternary High Cascades lavas (SI Appendix), indicating that much of the SP 77-24 hole has been oxidized.
maps and cross section - Oregon Cascades study site. (A) Topography, rivers (from USGS blue lines), stream gauges, lakes, and faults. Olallie North Spring (ONS) and HJ Andrews Experimental Forest (HJA) are labeled. (B) Surface bedrock ages (18), geothermal drill holes, and Quaternary volcanic vents (19). Labeled vents exhibited Holocene phreatomagmatic activity: Sand Mountain volcanic field (SMF), Blue Lake Crater (BLC), Twin Craters (TC). Gray areas are mapped as “Sedimentary deposits and rocks” in ref. 18. (C) Cross-section of swath topography and surface bedrock ages (N-S average of _4 km from Santiam Pass, pink box in panel A), with subsurface structures based on published geologic maps (SI Appendix). The proposed Critical Zone (CZ) state shift and physiographic “Western” and “High” Cascade provinces are labeled. (D) Temperature gradient versus depth in drill holes from panel (C). Near-isothermal or inverted temperature gradients define the “rain curtain.”
Public
Ð's©🇮🇸

Jour 19 : pierre

Ma plus belle prise volcanique de ces derniers mois : une part de lava cake dénichée tel quel lors d'une randonnée au bord de la coulée de l'éruption de décembre dernier (Sundhnúkur, secteur nord-est de Grindavik).

Une roche volcanique en forme de part de gâteau. On y voit 3 strates de couleur différente : gris foncé en bas, gris-mauve au milieu et gris clair en haut. La partie supérieure correspond en réalité à la couche inférieure d'une coulée de lave après durcissement. Autour de cette roche, d'autres morceaux de lave d'éruptions précédentes comme le Meradalir à gauche (août 2022) et le Litli-Hrutur à droite (juillet 2023). Derrière, un petit bouquet de pommes de pin, de la laine de mouton ou encore une coquille d'un oiseau sauvage.
#iceland#lava#eruption
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berndandeweg

After a month of increased #seismic activity in #Ethiopia, rumours of a #volcanic #eruption spread. From videos (eg links below) it is clear that heat is close to the surface, leading to boiling mud and steam appearing and a #mud #volcano, comparable to eg. Icelandic sites. No real #volcano with erupting #lava. Yet?
youtube.com/watch?v=KY2pfo5LqD youtube.com/watch?v=GZxp-wZ1IF

YouTubeThousands evacuated in Ethiopia due to volcanic activityBy Associated Press
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