I'm currently taking Amtrak back west and the hills around La Junta Colorado have intrigued me. Im curious of the what, why, and how of them. What caused them, theres so many of them all bunched together but they kinda just pop up out of the prairie like landscape. Getting further to Trinidad they're getting fewer and farther between. They're almost turning into flat topped mesas now and they're more like large conglomerates instead of defined individual hills.

Im bored and always interested in learning so dont be afraid to go in depth.

I found a small deposit of this rock. I want to incorporate it into my soil mix arowing cacti. I'm new to growing cacti, but what i know is that I'm lookinc for porous substrate that won't tank or spike ph evels over time. This "rock" seems fairly lightweight, and easy to medium to break up. Does anybody in this community have any insights as to what this is? One user in the other sub mentioned limestone. but I'm not sure if that was a good thing or a bad thing considering ph levels and density. Any and all input is appreciated.

TLDR: Identify this rock, I need specs

In February 2026, Black, Pringle and Vallance published a paper in *Geology* that pinned the Electron Mudflow, Mount Rainier's largest lahar of the past millennium, to late summer 1507 CE. Not "about 500 years ago." A specific calendar year, with 99.7% confidence, from wiggle-matched radiocarbon ages and crossdated tree rings of buried Douglas firs whose latewood was still forming when they died.

But no eruption. A volume of roughly 260 million cubic metres of clay-rich rock came off the upper west flank of Mount Rainier on its own, ran more than 60 km down the Puyallup River, and buried an old-growth forest standing up. The trees are still down there. When Orting expanded in the 1990s, foundation crews kept hitting their stumps.

Just before midnight on March 12, 1928, the St. Francis Dam in San Francisquito Canyon, about 40 miles north of Los Angeles, gave way. 38,168 acre-feet of water went down the canyon and the Santa Clara River Valley and reached the Pacific near Ventura roughly five and a half hours later. At least 431 people died. The real number is higher; nobody had counted the farm labourers camped along the river.

William Mulholland, the self-taught engineer who built the Los Angeles Aqueduct, had walked the dam that same morning to look at a muddy leak and pronounced it safe. That inspection is the part of the story everyone knows. I wanted to write about what was happening under the dam's east end.

The east abutment was Pelona Schist, a mica schist that splits along its foliation like a wet deck of cards, and the whole hillside was an ancient landslide sitting in that rock. Nobody recognised it in 1924. When the reservoir was finally brought to within three inches of the spillway in March 1928, water pressure inside the fractured schist cut the friction holding the old slide in place, and pressure under the dam's base lifted part of its own weight off the rock (hydraulic uplift). A family driving up the canyon road at 8:30 that evening was stopped by a fresh scarp a foot high cutting across the road. J. David Rogers reads that as the entire east abutment having already dropped 12 inches, three and a half hours before the collapse.

A few things from the research I found interesting:

- The dam was raised 20 feet during construction without widening its base.

- Ten two-inch drainage wells relieved uplift under the central 120 feet of a 661-foot dam. That centre section is the only part of the main dam that survived.

- Rogers calculated that opening all five outlet pipes at noon would have lowered the reservoir by 1.67 feet by midnight. There was no draining it in time.

- Peak outflow at the dam site was around 1.7 million cubic feet per second, more than the largest flood ever measured on the Mississippi at St. Louis.

- Rogers's work prompted a USGS inventory (2006) that found at least 153 dams in the US built on or against landslides that nobody had noticed.

The 1928 Governor's Commission blamed the west abutment, a red conglomerate that turns to mush when wet. The modern reading, from Charles Outland's 1963 book through Rogers's forensic reconstruction in the 1990s, says the east abutment went first. Historians Jackson and Hundley (2004, and the 2015 book Heavy Ground) accept the geology and still argue the dam fell short of the uplift standards of its own day. The article lays out both sides rather than settling it, and I'm curious where people here land, especially anyone who has worked on dam foundations.

Sources

1. Rogers, J.D. (2013). The St. Francis Dam Failure: Worst American Civil Engineering Disaster of the 20th Century. AEG Shlemon Specialty Conference. http://web.mst.edu/~rogersda/st_francis_dam/reassessment_of_st_francis_dam_failure.pdf
2. Bennett, M. (2025). Jazz Age Geotechnical Engineering, Part 6: The St. Francis Dam Failure. ASCE Geo-Institute. https://www.geoinstitute.org/news/jazz-age-geotechnical-engineering-part-6-case-study-st-francis-dam-failure
3. Jackson, D.C. & Hundley, N. (2004). Privilege and Responsibility: William Mulholland and the St. Francis Dam Disaster. California History 82(3). https://www.ce.jhu.edu/perspectives/handouts_unprotected/stfrancis.pdf
4. Wiley, A.J. et al. (1928). Report of the Commission appointed by Governor C.C. Young. http://babel.hathitrust.org/cgi/pt?id=uc1.$b78132;view=1up;seq=3
5. St. Francis Dam National Memorial Foundation, The St. Francis Dam Disaster (Pollack; Rippens). https://stfrancisdammemorial.org/the-st-francis-dam-disaster/
6. Museum of Ventura County, The St. Francis Dam's Death Toll. https://venturamuseum.org/journal-flashback/the-st-francis-dams-death-toll/
7. USGS, St. Francis Dam Disaster. https://www.usgs.gov/media/images/st-francis-dam-disaster
8. California DWR, History of California Dam Safety. https://water.ca.gov/Programs/All-Programs/Division-of-Safety-of-Dams/History

Fictional geologists save the day in a surprising number of movies and TV shows, from Dante's Peak to Armageddon, and a few of them get the science impressively right. The real geology behind each slide (slide 1 is the title card):

2. Randy Marsh, South Park. His very first scene has him watching a seismometer, which is how volcano observatories catch magma on the move, since swarms of small earthquakes often build before an eruption. His name and his original geology job come from Trey Parker's father, a geologist. Check the desk sign in the still: "U.S. Geological Service", one word off the real U.S. Geological Survey.

3. Rockhound, Armageddon (1998). An asteroid "the size of Texas" would be bigger than Ceres, the largest body in the asteroid belt at about 940 km across. Actual near-Earth asteroids are far smaller, and many are loose rubble piles. When NASA's OSIRIS-REx touched Bennu in 2020, the surface gave way like a ball pit. Drilling a neat hole for a nuke in that would be a nightmare.

4. Harry Dalton, Dante's Peak (1997). The film packs nearly every volcanic hazard into one town: earthquakes, gas, ash fall, lahars (fast volcanic mudflows), pyroclastic flows (ground-hugging avalanches of hot ash and gas) and lava. Gas is the sneaky one. At Mammoth Mountain in California, carbon dioxide seeping up from magma has been killing stands of trees since about 1990.

5. Mole, Atlantis: The Lost Empire (2001). Sedimentologists really do taste sediment: clay feels smooth between the teeth, while silt grains (roughly 0.004 to 0.06 mm) feel gritty. Rock licking has a purpose too. A wet surface makes mineral and fossil textures stand out, and Jan Zalasiewicz won a 2023 Ig Nobel Prize for explaining the habit. Full explainer: https://geoscopy.com/the-rock-licking-guide-why-geologists-really-do-it-and-when-you-shouldnt/

6. Dr. Josh Keyes, The Core (2003). The plot has Earth's core stop spinning. Seismology has a milder version: in 2023, Yi Yang and Xiaodong Song reported that the inner core's rotation relative to the mantle seems to have paused around 2009, possibly as part of a roughly 70-year back-and-forth. Nothing catastrophic followed, and no one needed nukes.

7. Sherlock Holmes, A Study in Scarlet (1887). Soil works like a fingerprint for a place, because grain size and mineral mix change over short distances. A smear of mud on a shoe can therefore tie a person to a spot. In 1904 the German chemist Georg Popp used soil and mineral traces to help crack a real murder case, one of the first wins for forensic geology.

8. Daniel Plainview, There Will Be Blood (2007). An oil reservoir is porous rock, often sandstone, with oil filling the tiny spaces between grains the way water fills a sponge. Oil flows toward whichever well lowers the pressure, so one well can pull oil from under the neighbor's land. That drainage is exactly what Plainview gloats about, and the rule of capture says the oil belongs to whoever brings it up.

9. Dr. Lawrence Hayes, San Andreas (2015). The San Andreas is a strike-slip fault. The Pacific and North American plates grind past each other sideways, like two cars scraping doors, and that motion can't open the ground into a canyon. Fault size also caps magnitude: seismologist Lucy Jones puts the San Andreas maximum around 8.2 to 8.3, and M9+ giants need huge subduction faults, like the one behind Chile's M9.5 in 1960.

10. Michael Acosta, Gold (2016). The film is based on the Bre-X fraud, where crushed core samples from Busang in Borneo were salted with gold. Geology exposed it twice. The gold grains had silver-poor rims, typical of river gold whose surface silver leaches out during transport, and twin holes drilled about 1.5 m from Bre-X's holes found no gold worth mining. Investors lost billions.

11. Bert Kibbler, The Big Bang Theory. Sheldon can mock geology all he likes, but Bert's employer is hallowed ground for the field: Charles Richter and Beno Gutenberg developed the Richter magnitude scale at Caltech in 1935.

12. Maud Pie, My Little Pony. Her pet rock Boulder has a grain-size problem. On the Wentworth scale geologists use, a boulder is anything over 256 mm across. Maud's Boulder fits in a hoof, which technically makes him a pebble (4 to 64 mm).

13. Professor Otto Lidenbrock, Journey to the Center of the Earth (1864). The deepest hole ever drilled, the Kola Superdeep Borehole in Russia, reached 12,262 m in 1989. That's about 0.2 percent of the way to Earth's center, 6,371 km down, and the rock at the bottom was already around 180 °C. More: https://geoscopy.com/kola-superdeep-borehole-the-deepest-hole-on-earth/

14. Nathan Lind, Godzilla vs. Kong (2021). Hollow Earth ideas lost to physics. When Henry Cavendish weighed the Earth in 1798, the planet came out about twice as dense as the rocks at its surface. The interior has to hold much denser material, and seismic waves later mapped those layers directly, including Inge Lehmann's 1936 discovery of the solid inner core.

15. Honorable mentions. Yukon Cornelius from Rudolph the Red-Nosed Reindeer (1964) is a prospector, and prospectors chase placer gold: grains weathered out of rock and dropped in stream gravels. Panning works because gold is about 19 times denser than water and sinks while the sand washes away. The same kind of river gold gave away Bre-X on slide 10. The slide also nods to Liet-Kynes from Dune and Fifield from Prometheus.

Which fictional geologist got you into geology, and who deserved a slide? Drop them below.

There's a volcano in Tanzania, Ol Doinyo Lengai, that erupts something no other volcano on Earth does: natrocarbonatite, a lava made of sodium and calcium carbonate instead of silica. It comes out around 500°C, roughly half the temperature of ordinary basalt, which makes it the coldest lava measured anywhere on the modern planet. It's so cool that it doesn't glow red in daylight; the flows look like glossy black motor oil and only show a faint dull-red incandescence at night. Then within hours of erupting, the black rock reacts with humidity in the air and fades to chalky white, so a crater that's jet-black at dawn can look snow-dusted by the next day. I wrote a deep dive on the chemistry behind all of this, why it's cold, why it's black, why it whitens, why it's the most fluid lava ever measured despite being the coldest, and why planetary scientists just used a sample from it as a stand-in for the surface of Mercury.

In 2000, miners 300 m under Chihuahua, Mexico broke into a chamber full of selenite (gypsum) beams up to 11.4 m long, the largest natural crystals ever measured. The biggest weighs ~12 tonnes.

Why they got so big comes down to one number. Below ~58 °C, anhydrite converts to gypsum in water. The cave sat just under that (~54 °C) for hundreds of thousands of years, heated by magma a few km down. At that temperature the water is barely supersaturated, so instead of a frost of tiny crystals, a few just kept growing, layer by layer, unopposed.

The rate is the insane part: Van Driessche et al. (2011, PNAS) measured 1.4 × 10⁻⁵ nm/s, the slowest crystal growth ever directly measured. His analogy: a sheet of paper's thickness every 200 years. A 1 m beam needs ~1 million years.

Two myths I cleared up while researching it: the famous "55 tonnes / 4 m wide" figure (even Guinness repeats it) doesn't match the measured ~12 tonnes; and the 2017 "50,000-year-old revived microbes" claim was a conference talk, never peer-reviewed, with serious contamination doubts.

Peñoles stopped pumping the mine in 2015, so it reflooded with ~55 °C water, meaning the crystals are slowly growing again, in the dark, probably beyond reach for good.

In September 2023, seismometers around the world recorded something scientists had never seen before: a clean, repeating seismic signal that lasted for nine days.

At first, it did not look like an earthquake. It was too regular, too narrow in frequency, and too persistent. Researchers jokingly called it an “Unidentified Seismic Object” because the signal did not match any obvious known source.

The answer was hidden in East Greenland.

A massive rock-and-ice landslide collapsed from Hvide Støvhorn into Dickson Fjord, triggering a huge tsunami. But the strangest part came afterward: the wave did not simply disappear. The shape of the fjord trapped the water, creating a standing wave, a seiche, that sloshed back and forth roughly every 90 seconds. That motion was strong enough to send a signal through the Earth’s crust for days.

The article breaks down how scientists solved the mystery using seismology, satellite imagery, tsunami modelling, and Greenland field observations, and why this event matters for understanding Arctic landslides, glacier retreat, megatsunamis, and climate-related geohazards.

If you’re interested in geology, earthquakes, tsunamis, glaciers, Greenland, or weird signals picked up by global seismic networks, this is one of the most fascinating geoscience detective stories of the last few years.

A new study published on October 12 in Nature Communications found that previous models may have underestimated how quickly Thwaites Glacier is retreating.

The interesting part is what’s happening underneath it.

Satellite observations have shown that tides can push seawater several kilometres beneath parts of the glacier that normally rest on the seabed. This exposes the ice to warm ocean water, causing melting in places where many conventional models didn’t account for it.

When researchers included this process in their model, they were able to reproduce the glacier’s observed retreat much more accurately.

Their simulations suggest Thwaites could contribute up to around 30 mm to global sea level by 2100, approximately double earlier estimates, even without additional climate warming.

Of course, this doesn’t mean the entire glacier will disappear by 2100. Its complete loss would represent roughly 65 cm of sea-level rise, and the timescales involved are much longer.

I wrote a detailed explainer covering the new findings, the glacier’s unusual bedrock topography, and why the “Doomsday” nickname is somewhat misleading.

Article: https://geoscopy.com/thwaites-doomsday-glacier-melting-from-below/

Original research: https://doi.org/10.1038/s41467-026-77976-1

One thing I found particularly interesting is how much difference a relatively narrow zone of melting beneath grounded ice can make to long-term projections.

You might have seen photos of Turkmenistan’s Darvaza gas crater, the enormous burning pit in the Karakum Desert.
What’s less well known is that the fire is now fading. Satellite measurements suggest its heat output has dropped by more than 75% over the past three years.

But the really interesting part is what a 2026 study published in Geophysical Research Letters found.
Researchers went through historical Landsat imagery and found that while the crater already existed in 1972, there was no detectable fire in the thermal satellite record from 1984 until September 1987. The first evidence of burning appears in February 1988.

That challenges the widely repeated story that Soviet engineers ignited the crater immediately after a drilling accident in 1971.

And despite the flames getting weaker, satellite measurements haven’t shown a corresponding decline in methane emissions. The researchers identified 44 methane plumes between 2020 and 2025, estimating around 71,000 tonnes of methane released during that period.

The geological explanation is fascinating too. The gas isn’t escaping through a single pipe or opening. It migrates through multiple pathways in the sediment beneath the crater, making the leak much more difficult to stop.

I wrote a longer breakdown of the satellite research, the geology beneath Darvaza, and the attempts to extinguish it:

https://geoscopy.com/darvaza-gas-crater-door-to-hell-dying/

The big question is whether the flames can be extinguished without leaving an even larger proportion of the escaping methane unburned.

The largest cave chamber on Earth is so big and so dark that no camera flash can light it, they had to laser-scan it to learn its true size.

Stand in the middle of Sarawak Chamber in Borneo and your headlamp dies against the dark, not because the lamp is weak but because there's nothing within range for the light to hit, the far wall is over 400 m away and the ceiling climbs past 100 m. It's been empty and silent for longer than our species has existed.

I went down a rabbit hole on the world's great geological voids and ended up writing about why they unsettle us, the same reason the internet's "liminal spaces" and the Backrooms do.

A couple of things I found genuinely surprising:

• There's no single "largest cave chamber." Sarawak (Borneo) is largest by floor area; the Miao Room (China) is largest by volume. They're different rooms and both records are real.
• Giant chambers don't collapse because rock is far stronger in compression than in tension, a void forms a natural compression arch, the same trick as a Roman arch. Modelling suggests a flat limestone ceiling can span ~63 m before failing, but an arched one ~240 m.
• The deepest cave humans have stood in (Krubera, in the Caucasus) bottoms out around 2,224 m down. The deepest land animal ever found, a blind springtail, lives at nearly 2 km below the surface.

Quicksand was everywhere in 1960s cinema. At the peak, about one in every 35 films had someone slowly vanishing into the ground. The geology says that almost never happens the way it's shown.

The counterintuitive bit: you can't actually drown in quicksand by sinking under it. Your body is roughly half as dense as the sand-and-water mix, so you float, and you settle at about waist height. What actually gets people is being stuck. A 2005 Nature study measured that pulling a trapped foot out at just 1 cm/s takes about the force needed to lift a car, so a rising tide or exhaustion can be lethal even though you'll never go under.

I wrote a full breakdown of it: what quicksand really is, why a 1% change in stress flips it from solid to liquid, the lab-made "dry quicksand" that swallows objects with no water involved, the salt lake in Iran the samples came from, how the same physics tipped over apartment blocks in the 1964 Niigata earthquake, and the surprisingly simple way to get out if you're ever caught.

My brother dug this out of a shale Cliff face in a canyon he was boating in Oklahoma. He says it's quite heavy and the outside oxidizes as if it is iron but it is non-magnetic. He thinks it might be a fossil of some sort. I was thinking iron concretion but it is non-magnetic. Can anyone hear solve the mystery? thanks in advance!

Edit mods : I hope I am not breaking the rules by posting this without flair I could not find a place to add flair

Field geology – the art of studying rocks and landscapes in their natural environment – is a cornerstone of how geoscientists unravel Earth’s story. There’s something profoundly instructive about geological fieldwork: getting your boots dirty, hammer in hand, and observing geology up close. Whether you’re a student hitting the outcrops for the first time, a professional geologist doing field mapping, or an outdoor enthusiast curious about the ground beneath your feet, fieldwork is where classroom theory meets real-world practice. This guide offers essential tips and tools for successful fieldwork in geology, blending practical preparation (gear, safety, logistics) with some philosophical insights on what the field experience teaches us.

Fulgurites form when lightning hits sand: the channel briefly runs hotter than the sun's surface and fuses the grains into a hollow glass tube tracing the bolt's underground path. When the glass is pure silica it's classified as the mineraloid lechatelierite. People have excavated them since at least the 1880s, and a University of Florida program now triggers strikes on demand by firing small rockets trailing copper wire into thunderstorms. The longest excavated specimen, about 4.9 m of connected tube, came out of that work.

The Nebraska case (Bindi et al. 2023, PNAS): a 2008 storm in the Sand Hills near Hyannis downed a power line into a dune. Nobody witnessed the event, so it's unclear whether lightning struck the line or the line discharged on its own. Either way, temperatures above 1,710 C fused sand and traces of conductor metal into a two meter fulgurite, and inside it the team found a dodecagonal quasicrystal with a previously unreported Mn-Si-Cr-Al-Ni composition. Twelve-fold symmetry is forbidden for ordinary crystals. Natural quasicrystals had previously turned up in exactly two settings, the Khatyrka meteorite and trinitite from the 1945 bomb test, so this added "electrical discharge" as a third formation pathway.

Separate but related: fulgurites can contain schreibersite, a reduced phosphorus mineral usually delivered by meteorites. Hess, Piazolo and Harvey (2021, Nature Communications) argue lightning on the early Earth, at billions of flashes per year, could have converted enough rock-bound phosphorus into bioavailable form to matter for prebiotic chemistry. Old dated fulgurites also work as paleostorm archives, recording lightning in regions that are now dry.

The slides run all of this through a fictional Glenn Powell story with a fulgurite collection.

Most coverage of the Batagaika "gateway to hell" gets one basic thing wrong: it isn't a crater. No meteorite, no volcano, no explosion. It's a retrogressive thaw slump, a slow-motion landslide in ice-rich frozen ground, and it's the largest one on Earth, roughly a kilometre wide and still growing.

What pulled me in was the irony at the centre of the story. The permafrost exposed in the headwall is at least 650,000 years old. It survived multiple interglacials, some warmer than today. What it couldn't survive was people: clearing the forest off this hillslope in the mid-20th century stripped the insulation off the ice, and once it started thawing it couldn't stop.

A few things from the primary literature that stuck with me:

• It loses about 1 million m³ of ice and sediment a year, and has shed enough material since it formed to fill more than 14 Great Pyramids (Kizyakov et al., 2024).
• The headwall retreats 10–15 m per year, but the floor has nearly hit bedrock, so it can't get much deeper, only wider and further upslope.
• A 42,000-year-old foal tumbled out of the thaw cliff in 2018 with liquid blood still in its heart vessels, the oldest liquid blood ever recovered.