Zoltán Sylvester

I am actually interested in rivers that are relatively unaffected by humans - e.g., zsylvester.github.io/post/counter...

It’s pointing up / to the north

Thick black line is the centerline of the Beni River in Bolivia. Circles that are tangent to the centerline represent the radius of curvature ag the location. Smaller circles = higher curvatures.

In this version the circles are colored according to the curvature; brighter colors = higher curvatures.

I have been experimenting with different ways of visualizing the curvature of meandering rivers. Plotting curvature in the context of the meanders themselves helps QC-ing the curvature data ⚒️🧪

BEFORE/AFTER the Dharali village debris flow today! 😱

Source: Manas Kabadwal

YouTube video by Nature lover ek pahadi JAI BABA KEDAR THARALI UTTARKASHI CLOUD BURST .

A catastrophic debris flow (not, as widely reported, a flood) has struck the village of Tharali in Uttarkashi, northern India. The video is truly terrifying. Very initial reports suggest there have been four confirmed fatalities and about 50 people may be missing.
www.youtube.com/watch?v=pVFn...

Spent some time in the Dolomites/Alps (to get away from everything for a while). The weather was far from perfect but having some constantly evolving low clouds around the mountains is not always bad

Rare ceratosaur fossil sells for $30.5 million | CNN A Ceratosaurus fossil that is one of only four known to exist has sold for $30.5 million at auction.

Another day, another dinosaur auction.

A world where dinosaur skeletons can fetch tens of millions of dollars within a few minutes at auctions is not a world where dinosaurs will long be accessible to educate and inspire everyone.

My thoughts for @CNN

www.cnn.com/2025/07/18/s...

The discourse surrounding precipitation changes in a warming climate (both public discussion and even scientific one at times) is complicated by widespread conflation of changes in averages vs extremes (and also actual vs *potential* evaporation/evaporative demand). [Thread]

Photo of the inside of our studio it’s a two-story high room with white walls and a white ceiling and a giant aluminum biomorphic undulating cellularly perforated sculpture standing in the middle

We’re opening up our studio to visitors on August 16th. Mark your calendars! We will have demos, you can shop our jewelry + puzzles, and also get sneak peaks of various sculpture projects we’re working on (in Catskill, NY)

Cross polarise light view of clinopyroxene (high birefringence), opaque oxides, masked brown biotite, surrounded by large twinned feldspars.

Been a while since I did a #ThinSectionThursday. Here is some beautiful larvikite (pyroxene monzonite): titan-augite, oxides and some biotite surrounded by large feldspars. This rock is widely used as a decorative stone but is equally appealing in thin section 🧪⚒️

I updated my web page (the old Hugo template I was using was not behaving well with the latest versions of the software) zsylvester.github.io. Animations like this one are now correctly displayed

It's hard to avoid recalling this passage from the English historian Tony Judt:

Two oxbow lakes of similar orientation, filled with yellow-brown muddy water, and surrounded by a dense, dark green forest.

Two lovely oxbow lakes with two perfect chute channels slicing through the point bars. Río Beni, Bolivia. Screenshot of PlanetScope data by @planet.com 🧪

NASA is being told to cancel 19 *active* missions to save $6B, which looks to be less than the ICE *hiring/retention* budget going forward.

I need people to let that sentence sink into their bones for a minute.

Viktor Orban banned pride events in Hungary, the people took it as a challenge and just had the largest pride march in their country's history.

R-hacking: the p-value is already practically zero but you are working hard to increase the r-value

A small bird with deep magenta and plum-colored feathers perches on a branch. It has a striking white cap on its head, a dark eye, and a short, straight black bill. The background is a soft, blurred green.

A little #SundaySnowcap

Male Snowcap #hummingbird at @tapirvalley.bsky.social #CostaRica

#birds #nature

Digital elevation model of the Grand River, South Dakota, USA. River floodplain in blue (high) to white (low), the rest of the landscape in orange (high) to green (low). The river meanders, the landscape on both sides of the floodplain is eroded with finger-like gullies.

A nice river, somewhere, meandering through a bit of glacial deposits and cutting into Upper Cretaceous shale and sandstone.
High-resolution prints are for sale on request (special edition!).

🚀 I am thrilled to share the final Table of Contents for my upcoming book, Introduction to GIS Programming: A Practical Python Guide to Open Source Geospatial Tools! Currently wrapping up the chapter on Distributed Computing with Apache Sedona. Aiming for a release before in two weeks. Stay tuned!

War on Science: Mapping Edition We’re not taking maps like Google or Apple, we’re talking like surficial and bedrock. We are talking about geologic mapping. And it seems the Trump administration isn’t interested…

The Grumpy Geophysicist (Dr. Craig Jones) brings us bad news about mapping and provides a nice overview of mapping for non-geos.

"...why, if you are pro-mining, would you want to hurt the Nevada program, where some of the big lithium deposits are? And some of the biggest hard rock mines?"

It tends to give me a headache 😄

Saying that ‘Learn to code’ is worse advice than ‘Get a face tattoo’ is worse advice than ‘Get a face tattoo’

As the sandstone is eroded, the concretions are harder to break up, and get concentrated on low-lying, relatively flat surfaces. Near Zebra Slot Canyon, Grand Staircase - Escalante National Monument, Utah. See this paper by Marjorie Chan et al for more details rock.geosociety.org/net/gsatoday...

Later on, reducing fluids coming from below remove the coatings and the sandstone turns white. As these fluids encounter oxygen-rich groundwater, iron oxides precipitate as concretions.

Moqui marbles line up in elongated patches that parallel eolian bedding in the Navajo Sandstone

A close-up view of the concretions

The lighter color of the rocks in the background is due to bleaching; some of that missing iron is probably in the concretions in the foreground

Moqui marbles are iron oxide (mostly hematite) concretions in the Navajo Sandstone. The iron comes from silicate mineral grains that break down during early burial. This iron ends up in thin iron oxide coatings on sand grains that give the characteristic pink to red color of the Navajo Sandstone. ⚒️🧪

No, you are looking at the side of a mountain. The pixels from a 3D model are projected on a vertical plane

This is work in progress and it will take a while to finish it but I find the process relaxing -- orthophoto of a mountainside in Utah, near Escalante, showing a deflation surface (I think) in the cross bedded Navajo Sandstone. Roughly a strike section relative to the dominant wind direction. ⚒️

Seafloor slopes control submarine canyon distribution: A global analysis Submarine canyon distribution is driven by slope inclination, linking tectonic and thermal forces to canyon formation.

Just out in Science Advances with @topotoolbox.bsky.social:
Submarine canyons preferentially form where the seafloor is steepest—not where rivers bring much sediment. Our global study reveals what controls canyon distribution and the world’s oceans.
www.science.org/doi/10.1126/...

Yes, 100 percent. I have already blocked a few of these ‘friends’ and I am pretty close to blocking another one

Facebook is great because you can find out which of your “friends” are really annoyed if you say bad things about the tangerine tyrant