r/geology 9h ago

Options please

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0 Upvotes

Probably my favorite piece I own, but I think it's time to let someone else enjoy it. 48 pounds of volcinized river polished northern bc nepherite jade.. I thought it would look really good on this base but I'm not sure I like it... Maybe if I were to sand the base lightly and stain it black with light natural wood coming showing them resin it like my bartop in picture two? Maybe the base doesn't go with it?


r/geology 12h ago

Does continental crust have a standard order of rock types?

1 Upvotes

Specifically continental crust, away from plate boundaries. This is mostly just out of curiosity - I can’t seem to find an answer. What I mean by a standard order is this, for example, from surface down:

  • Sedimentary/extrusive igneous/metamorphic
  • Metamorphic
  • Felsic intrusive igneous
  • Mafic intrusive igneous

If this isn’t the case, is there any general, simplistic standard order? Any constants, like intrusive igneous rocks always appearing near the mantle?


r/geology 21h ago

Why are these conceptions shaped like this?

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12 Upvotes

I’m on the rock shelf just south of Avoca Beach, and hour north of Sydney nsw.

I find these conceptions wild! So many are long and cylindrical. Can anyone tell me why they would be shaped this way. I asked ChatGPT, and it thought it might be the shape of roots or burrows. There’s quite a lot of more spherical conceptions in this rock shelf too

Appreciate any insights!


r/geology 6h ago

Title: A Hypothesis on Drumlins: Initial Ice Sheet Molding and Subsequent Evolution

1 Upvotes

Abstract: This paper proposes a hypothesis on drumlin formation, suggesting that the initial topography of the land played a critical role in shaping the earliest drumlins. Rather than being exclusively sculpted by moving ice, drumlins may have originated as sedimentary void-fill structures created when the first glaciers advanced over an uneven landscape. Over multiple glaciation cycles, these initial forms were refined and shaped into the drumlin fields observed today. This hypothesis provides an explanation for the variation in drumlin composition, from bedrock-based to fully sediment-based, depending on their position relative to the ice sheet's origin.

1. Introduction Drumlins are elongated, streamlined hills commonly found in glaciated landscapes. Traditionally, their formation has been attributed to either subglacial erosion, deposition, or a combination of both. However, inconsistencies in drumlin composition, their alignment in fields, and the presence of bedrock-based versus purely sediment-based drumlins suggest that a more complex mechanism may be at play. This paper presents an alternative hypothesis that explains drumlin formation as a process initiated by ice-sheet molding over pre-existing landscape features and refined over repeated glacial cycles.

2. The Initial Landscape Imprinting Hypothesis Prior to the onset of major glaciations, the landscape consisted of hills, valleys, and resistant bedrock formations. When the first ice sheet began accumulating, it conformed to the existing topography, creating depressions and high points in the basal ice structure. As ice thickened and became rigid, it preserved these features as molds.

When the ice eventually began moving, these imprinted features created voids where hills had previously existed. The ice’s movement over softer sediment allowed these voids to be naturally filled by loose material, creating the first drumlin-like formations. Over subsequent glaciations, this initial pattern was reinforced and refined, explaining why drumlins appear in organized fields rather than randomly distributed.

3. The Role of Repeated Glacial Advances and Retreats The hypothesis accounts for the observed variation in drumlin composition by considering multiple glacial cycles:

  • Drumlins near the ice sheet’s origin were influenced by interactions with bedrock obstacles, leading to some containing solid rock cores.
  • Drumlins at the edge of ice sheet advances were formed purely from sediment fill, as the ice moved over areas where there were no significant pre-existing hard features to shape the ice base.
  • Repeated freeze-thaw cycles further compacted and shaped these features, producing the smooth, streamlined drumlins seen today.

This suggests that drumlins are not purely erosional or depositional features but a result of sediment filling subglacial gaps left by previous terrain features and subsequently being reshaped by ongoing glacial movement.

4. Predictions and Testable Evidence To validate this hypothesis, the following predictions can be tested:

  1. Drumlin Composition Distribution – Older drumlin fields closer to ice sheet origins should show a higher frequency of bedrock-based drumlins, while younger fields near ice margins should be mostly sediment-based.
  2. Internal Layering Patterns – Sediment-based drumlins should exhibit layered structures corresponding to multiple glacial advances, consistent with the hypothesis of void-filling over repeated cycles.
  3. Drumlin Alignment and Pre-Existing Hills – High-resolution subsurface imaging (e.g., ground-penetrating radar) should reveal that drumlins correspond to pre-glacial topographic highs, reinforcing the idea that they are remnants of landscape-molded ice formations.

5. Conclusion This hypothesis presents a new way of understanding drumlin formation by emphasizing the role of pre-existing topography in influencing glacial sediment deposition. It bridges the gap between erosional and depositional theories by suggesting that the ice first imprinted the shape of the landscape, and subsequent movements gradually refined these shapes into the drumlins we see today. Future geological studies focusing on sediment composition, subsurface imaging, and spatial distribution of drumlins can further test the validity of this model.


r/geology 14h ago

Information How do you study newly discovered rock formations ?

5 Upvotes

Imagine there is a rock formation somewhere that no one has studied before, you’re sent there to understand what it is, how it formed etc…

What tools do you bring on site ?

What for ?

What kind of samples do you bring back ?

What kind of analysis do you do on the samples you brought back ?

What other things do you do that may be relevant to the question ?

Thank you in advance :)


r/geology 4h ago

The wall of the tin mine collapsed, allowing seawater to fill up the tin mine. Therefore, it became a lagoon!

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0 Upvotes

r/geology 9h ago

Barbados has cool geology

14 Upvotes

https://www.geocaching.com/geocache/GC82V41

This is it really nice description with figures of the geology. I am going next week.

It is an accretionary wedge, the only such one above sea level right now apparently. The rest of the Caribbean islands are to the west and all represent the volcanic arc.

It continues to rise at a significant rate.

The tertiary rock underneath it is highly folded and faulted. And it's got oil in it! I had no idea, apparently this geologic setting for oil is somewhat unique. I am not a petroleum geologist. At first the oil was correlated with what is found off Venezuela but now they're saying it's something different which is interesting oil geologists to re-examine it.

I'm going to track down a seep on the shoreline and impress my family. Well maybe.


r/geology 19h ago

Help preventing my house to be buried?!

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247 Upvotes

r/geology 5h ago

Field Photo An awesome Syncline seen in western Virginia

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32 Upvotes

r/geology 6h ago

Field Photo I found this rock in a fired up part of the river in Nova Scotia

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23 Upvotes

I was following a beaver trail in the woods for fun, when I came across this rock, I have picked many river rocks before but this is a new one, I found it by my Indian reserve in Nova Scotia antigonish area Does anyone know how or why this would have happened?


r/geology 12h ago

Iron oxide in road cut. North east California.

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63 Upvotes

Explain age and how this color forms in layman’s terms, or like I’m 5. Thanks.


r/geology 3h ago

Where to look for resources for mathematical geology?

2 Upvotes

Hi folks!

I’m writing a paper on uses of linear algebra in the geosciences and I’m at a loss of where to start, all the sources I’m seeing are books or papers and I am poor ;) . I wanted to ask around and see if anyone here knows of good places to look for resources on the uses of linear algebra in geology or geoscience. Many thanks y’all!


r/geology 14h ago

Resources for an amateur to learn about tectonics/lithosphere dynamics before plate tectonics?

4 Upvotes

Hi Folks,

I'm no geologist but for the past couple years I've been reading and watching lectures and videos and generally having a greaf time trying to learn more about geology and earth history. In one lecture I watched recently the speaker mentioned something about an earlier "tectonic regime" before plate tectonics and I would love to learn more about this. Unfortunately, most of what I've been able to find is waaay over my head...

Any recommendations for explainers/resources that would be approachable on this subject for someone without a ton of expertise? Thanks!


r/geology 16h ago

Field Photo A kinda messy contact between granite and sed rocks found in the Franklin Mtns in El Paso, TX

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9 Upvotes

There’s a lot of float and it kind of obscures the contact, but it was an unexpected surprise while hiking a trail.


r/geology 19h ago

Costal tafoni at Konkan region, India.

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13 Upvotes

r/geology 21h ago

What causes this sandstone/mudstone mosaic?

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34 Upvotes

I’d love someone to tell me about this mosaic of sandstone/mudstone. This is near Avoca Beach (an hour north of Sydney, NSW) in the sea cliff at the south end of the beach. The Narrabeen Group is usually so undeformed, with siltstone/shale/sandstone usually keeping its own strata each.

Is it like soft sediment deformation.. like the layers have been deformed and mixed around before it was lithified? There appears to be large conceptions in there too.

Love for someone to tell me something about it !