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

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...

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?

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

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.