Geoscopy | Geology, explained.

▶

▶ 876 ❤ 0 💬 0

Wanna buy a house in Alaska? PARODY but with real science. Alaska’s most walkable town: the whole community under one roof, fjord views, and slopes across the Sound on the move. Whittier sits at the head of Passage Canal, and most of its residents share one 14-storey tower. Fifty kilometres northeast, above Barry Arm, a slope of about 455 million cubic metres has been creeping toward the water. It moved 120 m between 2010 and 2017, as Barry Glacier thinned and pulled back from its foot. A glacier works like a doorstop: remove it and the slope has to hold itself up. A 2020 estimate put a worst-case wave at Whittier near 9 m. In 2021 the U.S. Geological Survey ran the physics with new seafloor and lidar data: waves above 200 m beside the slide, 500 m of run-up on the far wall, and just over 2 m off Whittier, 26 minutes after failure. The slope is heavily instrumented; the state’s August 2026 update lists it at activity level 1. The open question is closer: a 2024 survey found 43 moving slopes in Prince William Sound, 11 with tsunami potential, one on Maynard Mountain, directly above the town. In 1964, underwater landslides in the fjord put waves on the waterfront within minutes; 13 people died. The one action that matters: know the way to high ground and go when the warning comes. Twenty minutes is enough only if you use it. Sources: Dai, C., Higman, B., Lynett, P.J., et al. (2020). Detection and assessment of a large and potentially tsunamigenic periglacial landslide in Barry Arm, Alaska. Geophysical Research Letters 47(22). Barnhart, K.R., Jones, R.P., George, D.L., Coe, J.A., & Staley, D.M. (2021). Preliminary assessment of the wave generating potential from landslides at Barry Arm, Prince William Sound, Alaska. USGS Open-File Report 2021-1071. https://doi.org/10.3133/ofr20211071 Schaefer, L.N., Kim, J., Staley, D.M., Lu, Z., & Barnhart, K.R. (2024). Satellite interferometry landslide detection and preliminary tsunamigenic plausibility assessment in Prince William Sound, southcentral Alaska. USGS Open-File Report 2023-1099. https://doi.org/10.3133/ofr20231099 #geology #earthscience #scicomm #geoscopy #tsunami

▶

▶ 2.7K ❤ 0 💬 0

Nobody can actually prove how the Bahamas makes its sand. The argument has been running for over a century, and it's one of my favourite fights in geology. The sand in question is made of ooids, tiny limestone pearls, rarely bigger than 2 mm, built from concentric layers around a bit of shell or a sand grain. They only form in warm, shallow water that's loaded with dissolved lime and constantly moving. The Bahama Banks produce them by the trillion (sedimentologists genuinely call the place "the ooid factory"), and huge limestone formations all over the world, from Jurassic England to Triassic Germany, are made of almost nothing else. The textbook story says it’s pure chemistry. A grain rolls, picks up a coat of carbonate, gets sanded down while tumbling, and stops growing when the two processes balance out. That balance would neatly explain why they all end up the same size. Then people started cutting them open. Inside the layers there are fats, proteins and sugars, the residue of microbial films that coat every grain in those waters. So a second camp argues the microbes aren’t bystanders, they help build the thing. One team even modelled ooid growth using maths originally developed for brain tumours, and got the size limit right. A major review politely calls the whole question “highly contested,” which in the literature is fighting words. What would settle it is a sterile control, an ooid grown in a lab with no microbes present. Every attempt so far has come back inconclusive. The chef beef in the slides are made up. The argument and science is not. Sources: Diaz & Eberli 2019 (Earth-Science Reviews) · Trower, Lamb & Fischer 2017 · Batchelor et al. 2018 (Scientific Reports) · Pei et al. 2024 (Sedimentology) #geology #ooids #oolite #sedimentology #bahamas

▶

▶ 1.2K ❤ 0 💬 0

There is a volcano off Hawaii right now with its summit 975 metres underwater. It’s erupting. It has a name, Kamaʻehuakanaloa (renamed from Lōʻihi in 2021), and in a few tens of thousands of years it will surface and become the newest Hawaiian island. The system that guarantees this has been running for 80 million years. It works like a blowtorch under a moving sheet of paper. A fixed column of hot rock, a mantle plume, sits anchored in place while the Pacific plate slides over it at 7–10 cm a year, and every stretch of seafloor that passes gets a volcano burned through it. The result is a 6,100 km line of at least 129 volcanoes (Clague & Dalrymple 1987, USGS): young islands in the south, drowned peaks trailing all the way to Russia. Halfway along, the whole chain bends 60 degrees. The textbook said the plate changed direction 47 million years ago (Sharp & Clague 2006, Science). Then paleomagnetic data from the drowned peaks showed the “fixed” hotspot itself had been drifting south the entire early era (Tarduno et al. 2003, Science). Newer models say both moved at once (Torsvik et al. 2017, Nat. Comms). Still argued about. Nobody retires, either. Islands sink into atolls, atolls into flat-topped seamounts, and the eldest, Meiji, 80+ million years old, is currently first in line at the Aleutian Trench, about to be recycled back into the Earth. And measured from its seafloor base, Mauna Kea stands ~10,200 m. The tallest mountain on this planet is a mid-career member of this group. The idols are fictional. The franchise is not. Sources: Clague & Dalrymple 1987 · Tarduno et al. 2003 · Sharp & Clague 2006 · Torsvik et al. 2017 #geology #hawaii #volcano #hotspot #maunakea