(note: if you’re reading this in an RSS reader, you’ll probably be missing out on the artwork I did for this post. Make sure you click through to get the full visual experience)

Venus

A world of beauty, or a galactic volcano in sediment’s clothing? Only Hypocentre of Hypo-thesis can distil the ancient doom of the Cambrian on Venus!

Something catastrophic may (or may not*) have happened during the Cambrian on Venus.

Maria Brumm of Green Gabbro gives cibophobics another reason to fear cakes, as she compares a plum clafoutis to Venetian impact craters in What Planet is my Clafoutis From?

Like so many moments of culinary inspiration, this plum clafoutis is nothing like what I was thinking of prior to actually wandering into the kitchen to make dinner.

Earth

The Earth. A pale blue dot suspended in a sunbeam. The target of jealous and tyrannical alien invaders. And impacts! Geology Happens relays the shocking facts about Impacts from Space!

I am cheating somewhat since my post is about a phenomenon that happens here on earth as well as in space. That is the idea of impact craters.

Tuff Cookie from Magma Cum Laude tells of impactors too in Rocks in from space. Could this be the first wave of yet another alien invasion?

Anyway, spending so much time at the museum – around the meteorites, among other things – was one of the reasons I became a geologist.

Mars

The constant, unending invasions from Mars during the 1900s should have been horrifying enough, but now SamStag from cryology and co. makes us quiver in fear at the prospect of Rockglaciers from Mars !!! Will the red menace ever be defeated!?

From all planets and minor objects of the solar system, most similarities to features of periglacial regions on Earth can be found on the red neighbour – Mars.

And if the thought of glacial processes on Mars didn’t send shivers down your spine, Brian from Clastic Detritus informs us of Fluvial Deposits on Mars! Walk for your lives!

High-resolution mapping of planet surfaces (including Earth) from orbiting spacecraft is revealing the beauty and complexity of erosional and depositional landforms.

The Asteroid Belt

The inner Solar System could have bore five terrestrial planets. The smoldering remains of planet 4.5 are what make up the asteroid belt, where material unchanged since the dawn of the Solar System remains. Though there’s no perceived threat of alien attack from the asteroid belt, who can really be sure? Silver Fox of Looking for Detachment discusses Mining the Asteroid Belt, in what can only be described as a preemptive attack to deprive potential invaders of potential resources. Potentially.

But first off, mining in space – in the asteroid belt or anywhere else – is not likely to happen anytime soon, IMO. Numerous people, however, have been looking into it, perhaps at least as long as we have been actively exploring space, beginning with our 1960′s race to the moon.

Jupiter

The gaseous bully of the Solar System offers up intrigue for the bravest of volcanologists. And Dave Schumacher of Geology News gives us the terrifying details of Extraterrestrial Volcanism on Io! Will the space bound geo horrors never cease!?

What is all the lava that erupts on Io composed of? Scientists do not know for certain the composition of the lava, but based on spectrometer data, Io’s surface is covered with a mix of hot, basaltic or ultramafic silicates and a sulfur dioxide frost.

Saturn

The unfolding story of Titan should surely serve as a warning! Peter Polito over at Geology News regales us with tales of Titan Channels: What we know four and half years later.

One of the most fascinating things about the surface of Titan is that five years ago we knew nothing about it.  But with the arrival of Cassini and Huygens that has all changed.

Lockwood of Outside The Interzone also contemplates the channels of Titan and low temperature freeze-ray geology, as well as details of the moons of Enceladus, Europa and Miranda in A Fine Piece of Ice:

We knew there was a chance a chance of methane/ethane preciptation, we knew there was a chance of liquids on Titan. But the idea that dendritic drainage might form at 178 below zero Celsius never crossed my mind.

Pluto

Disregarded as a fully qualified planet, could the menace of an atmosphere make Pluto a body of geological interest? Yes! And Chris from Pools and Riffles heralds in the new threat of the Geology of Pluto.

The hardest thing about studying the geology of Pluto is the distance. Pluto is at a minimum 4.28 billion km from earth. A little to far for a rock hammer. At that distance, even satellites have problems.

The Entire Solar System

Cosmochemists (as I could claim to be), like the big picture. The REALLY big picture. Chuck at Lounge of the Lab Lemming tells us of the radioactive horrors that endured when the solar system was dragged kicking and screaming into the galaxy, in Isotope Park.

When’s the last time your non-geological friends told you their 6 year old loves ⁶⁰Fe?

The Entire Universe

MJC Rocks of Geotripper contemplates scarring the children of today with thought of the universe-sized scorpions and bears, but not as part of some sort of dome, in Done with Domes.

The ancients thought of the cosmos this way, and they made stories to go with the random arrangements of stars that formed bears and hunters and scorpions.

And speaking of space in its entirety:

You have read it. You cannot unread it. Stay tuned for more exciting geological tales in next month’s Accretionary Wedge. Your very survival could depend on it!

For those wondering, no I didn’t manage to get my thesis in on time. I’ve got a 4 week extension, though, so it’s not far off.

In the title comic book cover, illustrations of the Earth split in twain, the characters floating in space, and the terrifying martian are from various covers of the comic book series Mystery in Space and © DC Comics.

Just a reminder that posts for the Accretionary Wedge #13 are due this Thursday (or Friday), your time (25th or 26th of September). Check out the original post for submission details and get those little space themed articles rolling on in!

You may also want to check out the upcoming and previous hosts of the Accretionary Wedge here.

It’s my turn again to host the geoblogosphere’s blog carnival, The Accretionary Wedge. This month for the Wedges thirteenth edition the theme, as chosen by me, is:

Geology in Space (pronounced Geologeeeeee in Spaaaaaaaace).

Geology doesn’t just happen here on Earth, it’s happening everywhere there’s a small amount of silicates being drawn together by gravity. This month, give yourself a few hours, pick a body within the solar system, and tell the world about the geology that goes on there. You could talk about yardangs on Mars, the extreme tectonics of Venus, the enormous equaitorial ridge on Saturn’s moon Iapetus, what the HED meteorites tell us about 4 Vesta, or anything else that may tickle your geological interest.

The Earth is so huge and varied geologically, just think about what else is going on, on the other 7 planets and thousands of other bodies in the solar system.

I’ll be handing my MSc thesis (which deals with the formation of the solar system) in on the 25th of September, so that’s the date for everyone to get their submissions to me on the weird and wonderful things that have happened since. Either email me (chris (-then the usual symbol-) goodshist.com), or post a link in the comment thread of this post.

Happy writing!

Pictures and maps of all the volcanoes involved as well as links to more information will follow my retelling. My colloquial version of the Maori Legend for how Taranaki got where it is goes a little something like this:

Te Maunga o Taranaki (Mount Taranaki) once lived in the Central Plateau with the other volcanoes Ngarauhoe, Ruapehu and Tongariro. No doubt they often caught up and played cards with Taupo, Rotorua, Tarawera, and the countless other subariel volcanoes in the area and all was well and merriment ensued. However, the drop-dead gorgeous maiden Pihanga, also a shield volcano, had caught the eye of all the mountain gods (the large mountains) and they were all deeply in love with her (suckers!).

Going by the legend, she was quite something, draped in her green cloak of forest. Peace predictably didn’t last, as the unspoken volcanic law of not letting on who you’re hot for was broken by Taranaki as he made an advance old super-lovely Pihanga. This was quite extraordinary, and Tongariro got pretty angered. So annoyed was he, that a battle ensued between the two mountains (can you imagine that!? Holy crap that’d be awesome to watch!), and the earth itself shook, trembled and ruptured as the two gods battled, darkening the skies with ash.

When the dust settled (well, ash, pyroclastic flows, lava flows, lahars, collapsed ash columns, you name it), Tongariro, reduced in size greatly due to the engagement, stood close to Pihanga. Basically in volcanic terms, that meant the two were shaking up. Taranaki was quite annoyed and bitter that things hadn’t worked out his way. Tearing himself from his very roots, he left his home, running towards the setting sun to the location he now sits. Along the way his mumbling and grumbling gouged out the Whananui River and the Pouakai Ranges, which remains a barrier between Taranaki and the Central Plateau.

The frequent cloud cover over Taranaki is said to symbolise the mountain weeping for his lost love. In human terms, Taranaki is either a hopeless romantic or far too emo for anyone’s good.

Here’s a google map of the area with the volcanoes of interest mapped out:

View Larger Map

Here’s a few photos and paintings of Taranaki and co., just to help enhance the art theme:

[Show as slideshow]

Wikipedia links to information on the mountains in question:

• Tongariro,
• Taranaki,
• Pihanga

And finally, I’d just like to extend my congratulations to the geoblogosphere for reaching double figures in issues of its carnival. Next up: the Accretionary Wedge’s first birthday on the publishing of number 12 in August.

Episode 5 of the podClast is ready for download. You can grab the mp3 here (19.1 Mb, 33:18), or subscribe through iTunes here.

Today’s show discusses The Mars Phoenix Lander,

Participants

Chris – goodSchist

Jess – Magma Cum Laude

Show Notes

Notes on taming volcanoes with limestone and dolomite

There’s images from the Phoenix showing grains from the Martian surface.

Big Earthquakes Spark Jolts Worldwide? We had a discussion about that.

Ice quakes are a topic you may like to read about.

I managed to digress into talking about the ANDRILL project.

There’s the Geotimes article and the AAPG article about geoblogging. And Chris has a list of all the active geobloggers over at Highly Allacthonous. There’s also Aiden’s post about it all.

And here’s the link to the call for posts for the Accretionary Wedge #10.

Jess was right with her first guess, it was Tambora that caused the year without a summer (not Krakatoa). And the artist we couldn’t remember the name of was James M. W. Turner

del.icio.us/podclast

We have a del.icio.us account which can be found at http://del.icio.us/podclast. All the web pages and resources we’ve found and used in the discussions on the podclast can be found here. A conveniant way to browse per episode is to go to, for example, http://del.icio.us/podclast/episode5 (for this episode).

If you find a link to a topic that you’d like to hear discussed on the podclast, or have a link to a topic that’s already been discussed, you can add links to the podclast page through your own del.icio.us account.

When saving a link, include the tags for:podclast and episodeX (where X is the episode number – for example episode5). You can add more than one episode tag if the link applies to multiple episodes.

Next Episode

We like to have a new episode of the podClast every fortnight, so the next episode will be recorded on Saturday the 21st of June at 2300 GMT.

Contributing

If you’re keen to hear a specific topic talked about, or would like to join the discussion during the next episode (we’d really like a few more voices in there), either leave a comment below or email chris [the at symbol] goodschist.com. You’ll probably also do well reading the details on joining the podclast. If you don’t have the time to join us but would like to contribute a 3-5 minute audio clip to the show simply record it, make sure it’s an mp3, and send it to the address above [I'll add more thorough instructions at a later date]

Credit

The intro and exit music was Roots Fi Cool by Burning Babylon.

The splash image on the homepage is a section of the painting “The Fighting Téméraire tugged to her last Berth to be broken up” by J. M. W. Turner and the album art is from NASA.

Geologists normally have a slightly unfriendly attitude towards floral biota. It is, after all, one of the major obstacles normally preventing the viewing of outcrops. Geologists are also the people who look for, find and then think up fantastic new ways of mining petrological resources, like petroleum, natural gas and coal. The use of these products normally releases CO₂ and other greenhouse gases into the atmosphere, and unless this is your first interaction with the modern media in the last 20 years, I’m sure you’ve heard why this is problem. In a way, geologists have made it easier to use these products. But I’m hardly going to start laying blame for climate change, because this is a positive article. This is how I think geologists, scientists in general, and everyone else can help save the world. And it comes down to a single problem.

The Biggest Problem

The biggest problem with climate change and what’s causing it is very simple. The solution is also very easy (objectively). You literally don’t have to do anything. It’s a topic that no one (including the IPCC, overview here) seems to want to talk about. The main problem with climate change and the biggest problem currently facing the biosphere of the Earth is there are too many human beings. The solution is for humans to stop having so many children. It’s that simple. And I’m hardly the first to suggest it. With a universal one-child attitude and over a mere four or five of generations, we could quarter the human population (through absolutely non-violent means) to a more sustainable level. This would help to ensure the continuation of the species. Want to save humanity? Stop it from growing in size.

Suggesting this as a political goal or by the way of policy would be nothing short of political suicide, unless you’re at the helm of a totalitarian communist state (and even then, it doesn’t really work). The only way to achieve this is to make having one child the universal fashion (and keep it that way for a few centuries) and that somewhat runs against basic human nature.

The political problems surrounding that suggestion, have placed it firmly into the “too hard” box (no double entendre intended). But if you look at the problem objectively, the overpopulation of the planet is the root cause of the problem, and that’s one of the many fronts it should be tackled from (in a fair, humane manner, mind you. I’m a humanist after all and am most often in utter awe of some of humanity’s achievements and disgusted by its ill deeds).

During The Chronicles of Riddick, the petroleum-inspired Vin Deisel‘s sequel to Pitch Black, the story concentrates on a planet called Crematroia. So extreme are the conditions on this planet that I couldn’t pass up the opportunity to give it a once over with a geological eye.

To Vin’s credit, the movie is specific with its measurements including temperature, and the metric system seems to prevail (Vin’s character talks of grams and kilometres). The Crematoria field trip involves breaking the basic laws of physics. But if you can overlook that little problem and ignore heat dissipation as a naturally occurring phenomena there’s some alright, extreme geology to be had.

Figures

[Show as slideshow]

Crematoria – The Conditions

The portrayed gravity and atmospheric conditions require Crematoria to be an Earth-sized planet. The extreme temperatures of 700°C (973 K) on the day side and  -300°C (-26 K, below absolute zero) on the dark side, would require an orbital distance from its star (assumed by me to be sun-like), closer than that of Mercury’s (0.30 – 0.47 AU). That’s a diurnal temperature variation of 1000 degrees with a change of 200 – 700 degrees observed to occur over several seconds. That’s a hell of a lot of energy loss during the short (~3 hour) night.

In the movie the planet’s surface is dark, black, volcanic-looking rock, which bears a striking resemblance to your common basalt. Andesite would be possible, but not common given the slim change of crustal stability and the lack of plate tectonics causing hydration-melting of subducted slabs (and generating andesitic melts).

With Vin Diesel and other characters running over the jagged surface without breathing gear, it’s also a planet I’ll presume to have ~1 atm of atmospheric pressure, which undoubtably contains Oxygen, Nitrogen and other terrestrial gases (how could they breathe otherwise? Magic!?)

The Physics

I’m not a thermal physicist, but from what I understand, dropping 1000 K over the course of a few hours seems rather unlikely, especially when the lowest temperature is below absolute zero (this is, of course, impossible). A temperature drop of that magnitude in a heat-retentive atmosphere like the Earth’s is simply not going to happen. Case-in-point, last night, here at 41° South, the temperature fell to 14°C from 22°C during the day. And that was from ~8 hours facing and radiating heat into the cold, dark abyss of space. But let’s just assume for the case of the geology (won’t somebody please think of the rocks?), that all of this atmospheric physics is given a pass and we instead take a look at the rocks on the surface.

The Good Geology

Magma lakes would definitely be a feature on the surface (Fig. 5). Some basaltic magmas have been measured at temperatures as low as 750°C (in lava lake of Kilauea, Hawai’i)[1]. That’s a little above the maximum temperature cited in the movie with 700°C being the temperautre at the top of the volcanic clouds, rather than the bottom of the columns. The thermometer seen in the movie (Fig. 1) has a maximum reading of 700, so the temperature on the actual surface could be anything. You’d also get radioactive heating on a planet of that size, as well as an accumulation of heat energy and conversion of kinetic energy from the planet-consuming pyroclastic flows seen erupting along the planet’s terminator (Fig. 3 & 7). With that kind of heat energy, it’s a surprise the surface of the planet isn’t a magma ocean, but then again, that’d ruin the action sequences.

Speaking of those pyroclastic flows, I was delighted to see ash falling on the movie’s protagonists as they scurry across the surface during the night (Fig. 2). That kind of extreme temperature change probably would cause explosive surface volcanism, especially if there’s water and other volatiles around (as you get with a terrestrial atmosphere). Millions of cubic kilometres of ash would have to fall during the impossibly cool night, which is odd,considering most of the cooled material seen is not covered in white ash.

And on the topic of pure metals, when a space ship is exposed to the direct heat of the star, its metal partially melts (Fig. 8). Pure Aluminium has a melting point of 660°C, Titanium melts at a more hardy 1668°C, so it’d probably be a good idea for the bounty hunters who own the ship to re-plate it at some point.

The Bad Geology

This is a hell-like planet. It puts the conditions thought to have been common during the Hadean or on Venus (average temperature of ~460°C) to shame. However, despite the erosive power of planet-wide explosive volcanism occurring every 3 hours, jagged rocky outcrops and cliffs appear on the surface (Fig. 3, 4 & 5). Given that the gentle pitter pattern of rain over a few million years will eventually erode the Himalayas flat as they did to their predecessors [2], high, columnar basalt cliffs and wild jagged features are not likely to survive the erosive power of a massive volcanic explosion every 3 hours.

Despite their best efforts (to reasonably good effect), and ignoring the physics problems, Crematroia would be flat and covered in metres-deep ash deposits in the places it wasn’t a magma ocean.

References

1. http://www.minsocam.org/MSA/collectors_corner/arc/tempmagmas.htm
2. http://www.sciencedaily.com/releases/2003/10/031006071157.htm

All images used in this article, including the splash image on the front page/archives are © 2004 Universal Pictures.

In the image, from south to north are Mt Ruapehu, Mt Tongariro and Ngauruhoe, the volcanics associated with Lake Taupo (a caldera lake), the volcanics associated with Lake Rotorua, White island and then a string of sub marine and sub aerial volcanics that make up the Kermadec arc. All of these are marked with red stars. The white arrow-line shows the subduction trench that’s the result of the Pacific subducting underneath the Australian plate. The orange triangle is the outline of the Taupo Volcanic Zone. Then there’s Mt Taranaki marked with a “?“. It is this particular andesitic volcano that makes me, and many, many others go “hmmm”.

[Show as slideshow]

It’s a rather large feature (see satellite imagery above. The dark green is the rough outline of the surrounding national park), having produced a classical almost-circular flank. It’s still active (last eruption, though minor, was around 1800), and it’s young, having commenced eruptive activity ~130 Ka. The really weird part is, it’s not geographically in-line with the rest of the TVZ volcanics, being ~100 Km west of the TVZ (even Maori legend makes note of this). And it’s not geochemically linked with the TVZ, being enriched in Potassium and other Large Ion Lithophile Elements. For a volcanic zone that’s popped up through an established continent, it’s also rather lacking in enriched, assimilated continental material, resulting in a fractionated elemental makeup (Here’s a thorough Journal of Petrology article detailing Taranaki and contrasting it with Ruapehu). But the big question that really gets to me, and one I haven’t found a satisfactory answer to is; why is Taranaki there at all?

You can check out other “geohmmms” at this month’s Accretionary Wedge.

Images in this article were taken from Google Maps and Wikipedia.

These are the often seen but rarely thought about scenes in countless movies where someone sinks into lava and the idea that the Earth below the continental and oceanic crust is mostly liquid. Like a big pot of caramel being brought to the boil by a radioactive hotplate. Since there’s two topics, I’ll split this article into two sections, each tackling a single misconception.

That Sinking Feeling
You’ve seen river folk (Fig. 1) and terranauts (Fig. 2) befall the same fate. Tripping, falling and/or just plain sinking into lava. It’s not so much a silly misconception as it is applying common experience to an unknown situation with poorly thought-through variables. Lava is a liquid, after all, and when the producers of multi-million dollar movies or fantasy novel trilogies get to thinking about the last time they sat and washed themselves, likely in the bath all those months ago, it dawns on them that they pretty much tend to sink into the water, which is also a liquid.

Figure 1: Gollum sinks into the lava of Mt Doom trying to save the one ring. Notice the low viscosity of the lava. Screenshots are © Copyright 2003 New Line Cinema.

Figure 2: A member of “The Core” Terranaut team sinks, nay, splashes into lava, in a geode, thousands of Km beneath the crust. Sigh. Screenshots are © Copyright 2003 Paramount Pictures.

The above screen shots show lava, which is not water, and creatures sinking into that lava which are mainly water. This is a problem because the material they are sinking into is liquid rock with a density of at least twice that of water. Forget for a moment that the cause of death would be extremely rapid combustion, or that you probably couldn’t see the bodies sinking due to the smoke they’d generate. The problem with these scenes is that you’d float, very easily, on a body of liquid with a density of ≥2.5 g cm³. The Dead Sea has a density of ~1.25 g cm³ due to it’s extremely high salinity. Just to illustrate how easily you sink in a liquid this dense, here’s a picture of a dude floating on his back reading the newspaper in that body of water;

Now that’s how you relax at 300-odd metres below sea-level. From Wikipedia.

The human in that image has a density of ~1 g cm³, so therefore won’t sink into a liquid of higher density (1.25 g cm³). This, of course, is a very simple explanation, and completely disregards the fact that lava is hundreds of thousands of times more viscous than water – which would further reduce the ability of endoskeletal animal to sink. What is possible, however, is for lava to roll over the top of you, so don’t think you’re low density is going to save you should a lava flow come slithering your way. That’d just be highly dense on your part.

Fountains of Fun
Continuing on the theme of lava and it being liquid, let’s take a look at this impressive shot of a lava fountain from Hawai’i;

A 10 m fountain of delicious lava at Pahoeoe, Hawai’i. From Wikipedia.

You’ve seen lava flowing out of the ground, flowing from volcanoes, flowing here there and everywhere. So as someone who’s not studied the finer inner workings of the science of geology, you’ve likely extrapolated your observations and concluded that the mantle is liquid too. Well, you’d be wrong there. The mantle is solid, but has the unique ability to flow in the solid state.

The reason we know this is the same reason we have a pretty good idea of the structure of the Earth; seismology. Seismic waves come in two major forms when you’re studying deep structures, S-waves, which look like the letter S, and P-waves, which are bands of varying pressure. We know the density of the Earth, we know the speed at which S- and P-waves travel through materials of those densities and we can tell how far away an earthquake was by measuring the time between the P-waves arriving and the S-wave arriving. We can also measure how and where these waves refract over different layer boundaries (Fig. 5). We can do this because the mantle is predominantly solid, which is good, because S-waves can’t travel through liquids. This is the same reason we know we have a liquid outer core; S-waves from large earthquakes don’t make it through the core. This is also frustrating, because it means we can’t see the basic structure of the inner core – which we presume to be mostly solid iron and nickel.

Figure 5: Paths of the waves from a large seismic event refract and are measured at various locations around the Earth. From Wikipedia.

So next time you think “I wonder how great it’d be to swim down through the mantle in a flame retardant suit”, stop and think again. Because not only would you have a hard time sinking into the lava, you’d also hit a solid wall, as it were – the mantle.

The splash image used on the front page for this article was source from http://www.volcanos.ms/

First up is Andrew Alden from About:Geology who proudly display two of his favourites;
A Multiply Fractured Mudstone

A cherty mudstone was fractured and invaded several different times by mineral-depositing solutions, then nicely rounded in the Pacific surf.

and a Serpentinite Boulder

Photos can’t capture all the color and textural appeal of this serpentinite specimen, polished by deep movements in the California Coast Ranges.

Next up, Chris Rowan from Highly Allochthonous gives us a desktop full of Komatiite;

I’ve been meaning to discuss this one for a while: even though it’s not the prettiest in my collection, it tells a very interesting story about the early Earth.

Kim from All My Faults are Stress Related gives us a deskcrop with dizzy feldspars

If you want to know just how a rock changed shape, it helps to have a way to tell apart pure shear and simple shear. Generally, you need to find some kind of object that has tracked the movement – and this rock has one.

Brian over at Clastic Detritus gives us a trio of his favourites, a couple of which are from the Permian (!), which I’m chronologically jealous of;

Stopping along Highway 62/180 in between Guadalupe Mtns National Park and Carlsbad Caverns is a favorite for geology field trips of any kind. At this location, you are not in any national park and can smash and grab as much of this rock as you want.

A submission from Ron Schott gives us Bushels of Deskcrops;

See how many of the deskcrops you can identify on your own – when you recognize one you can “Take a Snapshot” and add a comment.

Jim Repka from Active Margin has a fulgurite sample to tell us about. And to be honest, fossil lightning sounds amazingly cool;

The subject of fulgurites, or fossil lightning, came up and I explained that quartz has a melting point of about 1600 degrees C, a temperature easily achieved in the near surface, though in very wet soils the charge can be dissipated pretty rapidly.

Lab Lemming gives us a rundown of their Trophy rocks;

My first trophy rock is a 4 kg boulder of the Lavras conglomerate from the Tombador formation of the mid-Proterozoic Espinhaço Supergroup.

And to round out the deskcrop theme, here’s all of the deskcrops described by thermochronic from Apparent Dip;

• An early Cambrian shale
• Some mantle xenoliths
• and ventifacts from Death Valley

Thanks a lot to everyone who’s participated.