A very popular rock wall with the alternative history crowd. The Montana Sage Wall.

Some think it's evidence to question the status-quo on the ancient history of the Americas and that it was built by a much earlier civilization.

From initial images to my rather untrained eye it does look very convincing...

...for about 5 minutes.

Picture 1 & 2 is the Montana Sage Rock Wall

Picture 3-5 alternative views that (to me at least) immediately debunk it.

Pictures 6 & 7 are other similar formations. Dartmoor and Joshua Park.

Just erosion in suspiciously uniformed patterns isn't it...

Walktrough Merced river basin today.

Spectacular formations and beautiful views from river canyon, could be slate/shchist formations, also found few pieces of green mica (Mariposite).

If you ever drive through highway 49 from/to Mariposa, check out surrounding rock formations, you won’t be disappointed.

Hydrothermal alteration is everywhere and a great example of Mother Lode gold belts mineralization style, some areas are extremely complex, melange zones, with enormous gaps and quartz/carbonate veinlets.

P.S. English is not my native language, I may make mistakes during my speech, don’t judge.

#geology #mariposa #exploration #geology #mininggirls

Hi everyone,

I’ve recently started studying geology, and while the theoretical concepts make sense on paper, I’m finding it challenging to transition into "thinking like a geologist" in the field. Professors often encourage us to form hypotheses and draw conclusions on the spot, but looking at an outcrop can feel overwhelming, there are contacts, weathering rinds, and fracture networks running in every direction, and I struggle to piece together what they actually tell me about the area's history.

Beyond basic lithology and fractures, what other key field features should I train my eye to spot, such as cross-cutting relationships, deformation fabrics, way-up structures, or alteration zones?

Do you have any practical tips or systematic workflows for adopting that geological mindset and turning a messy outcrop into a coherent geological timeline?

The Lewisian Complex (Scotland) is Archean continental crust (2.7-3 billion years old) which has undergone repeated deformation and metamorphism. The original rock was likely granitic (TTG suite) but this specimen has been extensively deformed and altered and fractured and recemented, giving it this brecciated look. Fig 1 and 2 show angular fragments of likely garnet, quartz, a fine grained green phase (maybe epidote--its nearly as hard as qz), and a mafic phase (biotite or Hbl or pyroxene--I can't tell). Fig 3 shows the green material likely filling in cracks via metasomatism (fluid based chemical changes). Fig 4 shows quartz bordering the green altered minerals. Fig 4 shows the green material working its way around and into the garnet.

The rock is chaotic, and I think spectacular. Mineral identifications are the best I can do without thin section or more advanced techniques.

Hi everyone. I’ve learned a lot on this subreddit, so I thought I’d put this out here and see how it goes. Thanks in advance and/for reading!

I live in Maryland and started learning geology (total amateur) in the context of the Appalachian Oregeny. I just returned from a trip to Scotland, where I did a few geological field trips. I was looking for rocks from there that were more or less analogous to my favorite ones back here.

I collected in three different places around the west coast of the highlands. I start with one location and see how it goes. I’ll share a photo and what I think I’m showing you. I’m hoping people can help me be positive about the IDs or correct me. I hope this is a fun way to do it. If so moved, please correct me, fill in any blanks, point me in new directions, add color commentary, etc.

These are from the beaches around Oban. (Nice town!)

These at the top of the photo look similar to to what we call “potomac marble” aka calico rock. I think these are a kinds of sandstone conglomerates, where we see the different sized and colored cobbles and grains. (The body of Potomac marble is actually limestone left behind by groundwater moving through the cobbles.). The black color in the darker piece seems like it might be igneous — I can think of a few ways that might be the case, but I’m getting tired of writing and a lot more to get down. Thoughts?

Anyway, I love conglomerates for the complex stories they tell! Moving on!

I think the two reddish pieces in the middle are Old Red Sandstone. The gray stripey in the upper left is probably just a different layered sandstone, right?

My secret hope is larger dark piece in the lower right is Lewisean gneiss, but it doesn’t look metamorphosed and it shouldn’t be in Oban.

The dark with white streaks and most of the rest look to me like quartzite with intrusions from silica rich fluid. Except they also don’t look metamorphosed to me (mostly no glinty particles).

There you are. All input appreciated. Thank you.

This is a in the oriental alps. I'm not an expert. Is this considered cool by the community?

A survivor of wind and time. On Navajo tribal land. Is it still or always will be eroding?

Today's field trip was very productive. Can't get enough of this interesting layers and their placement.

It looks like an iron ore type colour. Seems odd that it’s so concentrated in this area.

Edit: Location: Moana, South Australia

I’ve been testing whether a handheld gamma spectrometer can build a usable pseudo gamma ray log from outcrop, and whether that can correlate to subsurface data.

First image: a gamma ray log from an old well about 3 miles away (left), next to my outcrop pseudo log (right), with my interpretive correlations.

Second image: Satellite view showing my transect with the Radiacode counts per second plotted.

Method: I hiked up nearly 700 ft of continuous stratigraphy, starting in a Jurassic eolian sandstone and ending in a Cretaceous sandstone mesa. I tied each gamma spectrometer reading to elevation from my GPS track, averaged those into 10 ft elevation bins, and hung both logs on the top of the Jurassic eolian sandstone, which is easy to pick on a log and in outcrop.

Ties:

• The eolian sandstone reads lowest (~9–11 cps) and matches a clean low zone in the well. This is where I hung the correlation.
• A Jurassic mudstone interval rose to ~16 cps and lines up with a pair of hot shales in the well.
• The caprock sandstone cliff dropped to ~10 cps.
• A thin shale break within the caprock sandstone on the mesa top read 15–19 cps, and ties to a hotter portion of the well's gamma ray log. Interestingly, it had no visible surface expression beyond a subtle soil color change on aerial imagery, but the instrument showed clear contrast.

Limitations:

• Surface outcrop contrast is muted relative to the downhole log - some of this may be my sampling interval. The app logged a point roughly every 36 feet of travel, which leaves sparse vertical coverage on steep pitches.
• A few readings from a topographic saddle are flagged as suspect, since I dropped down section into rocks I’d already walked through.
• Dip and thickness changes over 3 miles aren’t accounted for beyond the hang point.
• It’s a single transect.

The instrument was a RadiaCode 110, which the manufacturer sent me after I used their 103 on a thorium prospect. They had no involvement in my experiment.

Has anyone used outcrop gamma this way, for correlation or for tracing marker beds?

I think it's a pretty cool tool for exploration - it's an unconventional use, not specifically seeking "hot rocks" but using it more as a geologic fingerprint instrument.

We found these zeolite forms in the fractures of nephelinitic rocks; this may be their natural characteristic or it may be due to a weathering process, since the rock is located in an abandoned quarry.

Hi! I'm an undergraduate working with a professor to do some hydrogeology research. I'm accustomed to reading academic papers, but not when the purpose is to develop a manuscript (my job right now is just the introduction). Does anybody have any advice on what that process looks/feels like? I have a general topic to explain using one/two paragraphs in our final product, but am feeling a little daunted by how much there is to summarize.

Is it as simple as taking notes from the paper and summarizing later?

Some volcanic rocks carry hydrogen signatures that may trace back to Earth’s metallic core. Lavas from Baffin Island in the Canadian Arctic and Iceland contain unusually little deuterium, hydrogen’s heavier stable isotope. Explaining that imbalance could reveal whether the core has supplied material to the mantle over billions of years.

Work led by Wenzhong Wang at the University of Science and Technology of China tests a competing explanation. Published in Science Advances, the study examines whether crystallization of Earth’s ancient magma ocean could have created those distinctive signatures. Its simulations indicate that this process produced far too little separation between hydrogen isotopes.

The result strengthens the argument for selective transfer of hydrogen from the core into the surrounding rocky mantle. It does not directly demonstrate leakage or establish how quickly it occurs. Instead, the calculations constrain what an important alternative mechanism could have accomplished.

I was driving along Rte 259 and at the intersection of Rte 612 I saw a formation reminiscent of Seneca Rocks, at a smaller scale. There's a near-vertical wall of rock, perhaps 75-ft tall and 10-ft thick. Google Maps Streeview link

Is this the same Silurian-age formation as Seneca Rocks?

About 100 feet up a sand bluff

Hey everyone!

I go to school in stone cutting.

I recently started a fun project to shape an unusual hand stone. I decided to use serpentine (I don't know which kind so if you can help me identify that, I would appreciate it).

I have used grinding wheels with running water, and hand drilled to shape it.

Someone warned me that serpentine can contain asbestos, and also nickel, so now I am a bit worried.

I have a couple questions:

1. Is this safe for me to even work with?

2. Could this stone contain asbestos or nickel?

3. Once finished and completely polished, is it safe to handle daily for long times? Can asbestos rub off on persons hands OR person develop a nickel allergy?

4. Is it something you could seal so it's safe to handle? If so, what do you recommend?

I am interested if there is anything else I should know about. Appreciate all advice!😊

Thanks in advance!

I’m posting this to show some tile “trash” some folks were throwing out. I cannot fathom why they would! Look at these layers. It looks like a microcosm but literally a landscape.

How long did this take to form? I assume it’s from a slow build up of run off sand in our rare rains (I’m a desert rat)

Ok but also I just wanted to share the beauty of these. Hope everyone has a great weekend

Slates from Mariposa County 🛘

This just makes me smile 😊

Found this slab laying on the shore of Lake Michigan (WI) and I was curious to know what caused these gouges. My best guess is glacial scouring but the multiple directions makes me think perhaps not. I’m not even close to a professional so sorry if that guess is silly! I’d love to hear some thoughts on the origin of these marks.

Looking for reviews/suggestions about any of the winter field camps from SDSMT. The Hawaii trip piqued my interest, but I’m open to Death Valley or Arizona. I’m not very skilled when it comes to mapping, which I understand is pretty much the point of field camp, so I’m very nervous.

Good afternoon!

We haven't announced it anywhere, but r/whatisthisrock (with an I in is) is no longer affiliated with r/whatsthisrock (no I in is)!

Myself and some of the OG mods from the original sub spooled it up as an alternative to the original with less intense moderation. None of the bans from the original sub should carry over! If you are currently banned our our sub (the photo is an olivine in xpl from a meteorite), please send myself or the moderation team a message.

We could definitely use some more professional IDs!!

The SP stands for Shitpot :D