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Geology of the Tour de France @geotdf.bsky.social · 24/07/2026

Alpe d'Huez day! Two years ago, Marjolein made this clip for the @le-tourdefrance.bsky.social Femmes about how the Alpe is folding without breaking! Enjoy the climb! And the spectacular folds...

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Geology of the Tour de France @geotdf.bsky.social · 14/07/2026

Three years ago, Marjolein Naudé made this clip about the Puy Mary, the Cantal volcano's highest peak not far from today's finish line. It was then the finish for a stage in the @letourfemmes.bsky.social! @uugeo.bsky.social

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Geology of the Tour de France @geotdf.bsky.social · 14/07/2026

Today's Tour de France stage ends at Le Lioran, at the top of the Cantal Volcano, Europe's larges stratovolcano. Two years ago, we made this clip there, our favorite :) How volcanism led to the invention of the bicycle! @vanhinsbergen.bsky.social @uugeo.bsky.social

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Geology of the Tour de France @geotdf.bsky.social · 14/07/2026

I'll do one today, but it's an oldie! I'm fine, life took new turns :).

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Geology of the Tour de France @geotdf.bsky.social · 20/05/2026

Come again? What did I write that warrants that? 😂

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Geology of the Tour de France @geotdf.bsky.social · 20/05/2026

Carrara limestones are used for tiles and construction, are the standards for material science and isotope geochemistry (δ13C, δ18O). It's hard and homogeneous and excellent for architecture and art, such as the Pantheon or Michelangelo's David. And as subsurface for hard races!

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Geology of the Tour de France @geotdf.bsky.social · 20/05/2026

Marble originates as limestone that gets buried (here: to ~18 km depth) and heated (~500-600°C) by geological processes (Apennine mountain building), and then recrystallizes. Limestones are soft, compacted grains and fossils (right), marbles are hard, intergrown crystals (left).

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Geology of the Tour de France @geotdf.bsky.social · 20/05/2026

The Giro will pass Carrara today! The Carrara marble mines are Earth's largest. Since Roman times, some of the purest marbles in the world, used for iconic architecture and art, have been excavated in over 650 quarries.

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Geology of the Tour de France @geotdf.bsky.social · 10/03/2026

In case you wondered why GeoTdF is silent: we went incognito and trained to become pro. Today, we ended at nr 116 in Paris-Nice 😎 🦖 @teamvismaleaseabike.com @appysluijs.bsky.social

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Geology of the Tour de France @geotdf.bsky.social · 10/03/2026

Nolan, exactly the opposite actually. The resistant stuff is at the top (sandstones). The slopes are made of clay, and once erosion gets through the hard top, it’ll rapidly erode to make steep hill sides. And those get steeper by landslides.

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Geology of the Tour de France @geotdf.bsky.social · 18/10/2025

So today’s winner will have to dig deep for his win. But we advise not to dig too deep…

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Geology of the Tour de France @geotdf.bsky.social · 18/10/2025

Critical taper is the equilibrium angle of a wedge-shaped agglomeration of material that is bulldozed up (tectonically or otherwise). That angle depends among others on material properties, but piloshite makes slopes of up to 16%!

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Geology of the Tour de France @geotdf.bsky.social · 18/10/2025

There is no proper geological definition of the sediment association of the VAM subsurface, but among some geologists it is casually referred to as piloshite. Piloshite is an excellent material to explain 'critical taper theory' to students.

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Geology of the Tour de France @geotdf.bsky.social · 18/10/2025

It is rich in plasticite, contains iron accretions and abundant bituminous (i.e., organic material-rich) clasts, and may contain elevated heavy metal traces. There are plenty of ichnofossils (i.e., fossil footsteps) of giant caterpillars.

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Geology of the Tour de France @geotdf.bsky.social · 18/10/2025

Geologically, the Col du VAM deposits are best described as a sedimentary mélange, a poorly sorted, polymict (i.e., with elements of varied composition) and poorly stratified (i.e., layered) agglomerate.

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Geology of the Tour de France @geotdf.bsky.social · 18/10/2025

Those glaciers also bulldozered sand and gravel into hills, but the sediments that make the Col du VAM clearly 'unconformably' overlie the ice age deposits and must therefore be younger!

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Geology of the Tour de France @geotdf.bsky.social · 18/10/2025

The #TourofHolland gives us the opportunity to introduce the geologically most puzzling mountain of Europe: the Col du VAM! The Dutch province of Drenthe is world-famous for Pleistocene ice age erratics: blocks of gneiss and granite that were transported from Sweden and Finland by giant glaciers.

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Geology of the Tour de France @geotdf.bsky.social · 17/10/2025

During the Holland Tour, the peloton will pass the Geulhemerberg! See @melanieduring.com's clip about the treasures hidden along the climb! www.youtube.com/watch?v=ZkM7...

youtube.com

TDFF 2024 - Stage 4: The spring day on which the dinosaurs died

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 15/10/2025

And check out our 2-minute clip, with @vanhinsbergen.bsky.social about the Alblasserwaard's history, made last year for the Tour de France Femmes! www.youtube.com/watch?v=IZSZ...

youtube.com

TDFF 2024 - Stage 2: Living on land below sea level

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 15/10/2025

The Holland Tour is racing through our backyard! See this blog we wrote last year about the geology of the Alblasserwaard, the scene of today's stage :) And don't forget to listen to @josebeentv.bsky.social 's reporting at Eurosport! www.geo-sports.org/2024/stage-2...

geo-sports.org

Stage 2: Tidal | Geo-Sports

Three large tidal channels in the Rhine-Meuse mouth region of Dordrecht and Rotterdam in the South of Holland feature on stage two of the Tour de France

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Geology of the Tour de France @geotdf.bsky.social · 23/08/2025

So, some background for the start of @lavuelta.bsky.social…and oddly, the best way to do that is by telling you about the geology of Milano-San Remo 😃. The first days will be about the Po Plain and the Ligurian Alps! Enjoy! www.geo-sports.org/2024/geology...

geo-sports.org

Geology of Milan-Sanremo | Geo-Sports

We explore the geology of Milan-Sanremo with lost oceans, colliding continents plus a bit of risotto and wine.

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Geology of the Tour de France @geotdf.bsky.social · 02/08/2025

The Tour de France Femmes is climbing the Alps! Did you know the Alps are made of cheese? @vanhinsbergen.bsky.social explains in this clip! youtu.be/7wkFVQaMdo8?...

youtu.be

GeoTdF 2023 - Stage 14: The Alps are made of Cheese

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 02/08/2025

And the Swiss Cheese that is the Basque subsurface, and that makes for all the steep climbs! youtu.be/kCiXOFIMtZU?...

youtu.be

GeoTdF 2023 - Stage 2 - Swiss Cheese

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 02/08/2025

Or the world-famous boundary between the Cretaceous and Tertiary - the end of the dinosaurs - exposed in Zumaia! youtu.be/5yBTkUd3RWE?...

youtu.be

GeoTdF 2023 - Stage 3: The Book of Earth History

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 02/08/2025

The Classica San Sebastian will race along the Basque North Coast! @vanhinsbergen.bsky.social made some clips about the beautiful geological goodies of the Basque Country! The trace fossils in the Black Flysch for instance! youtu.be/BWGPKmuo6Zw?...

youtu.be

Trace fossils in the rocks along Stage 3 of the 2023 Tour de France!

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 31/07/2025

The TdFF races through the Devonian of the northern Massif Central today. Marj and @vanhinsbergen.bsky.social imagined racing a Tour stage back then, 400 million years ago, in this ‘23 clip! 🐟 youtu.be/VFXoz3pSPec?...

youtu.be

GeoTdF 2023 - Stage 12. Fishing in the Devonian

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 27/07/2025

Ooh…I don’t know. And that is a problem 😃. If I figure it out, I’ll let you know!

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Geology of the Tour de France @geotdf.bsky.social · 26/07/2025

And why is the Jura such a strange, croissant-shaped mountain belt in front of the Alps? Marj will tell you! youtu.be/CMeyN5AMGAU?...

youtu.be

TDFF 2024 - Stage 6: How the Jurassic got its name

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 26/07/2025

Racing through the Jura today! In ‘23 and ‘24 we made two clips about its geological wonders! Like dinosaur footprints! youtu.be/N7hmLLasZrk?...

youtu.be

GeoTdF 2023 - Etappe 19. With a trace of dinosaur

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 22/07/2025

Clearly, geology raised its ugly head again - literally - to make the Ventoux. And its structure has funny ways in influencing the race 🤓🤠

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Geology of the Tour de France @geotdf.bsky.social · 19/07/2025

One more Pyrenees stage! And luckily, we have one more Pyrenees clip! How the deepest rocks end up on the highest peaks! youtu.be/0t4EifLi-zU?...

youtu.be

GeoTdF 2023 - Stage 5: Earth's mantle

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 17/07/2025

While watching the ride to the Pyrenees, it's always striking how abrupt the transition is from the flat lands of the Aquitaine basin to the steep mountain slopes. Two years ago, Marj Naudé explained where this sharp change comes from! youtu.be/H7YIk3DnCug?...

youtu.be

GeoTdFF 2023 - Stage 7: From plains to towering mountains

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 14/07/2025

While riding over the Cantal volcano 🌋 - Europe’s largest, it’s time to tell the story how a volcanic eruption led to the invention of the bike! @vanhinsbergen.bsky.social @uugeo.bsky.social youtu.be/mLzFcPAZNAA?...

youtu.be

TdF 2024 - Stage 11: Volcanism and the invention of the bicycle

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 14/07/2025

A ride through the volcanic fields of the Massif Central today! Time to tell the story of Mary again! Take it away, Marj! youtu.be/6LPwKGLCHFU?...

youtu.be

GeoTdFF 2023 - Stage 2. Mary, queen of volcanoes

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 07/07/2025

And humans have used the dry North Sea to migrate from France to England and back during the last 800.000 years, depending on the climate state. And when there was enough ice, they could also walk to Ireland! No ferry needed. Or cycle, if they had invented the wheel.

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Geology of the Tour de France @geotdf.bsky.social · 07/07/2025

The wind picked up the silt from these rivers and spread it around. This wind-deposited silt is known as loess, and northern France is covered by it. Loess is a nightmare for anything on wheels, so early on, big cobbles were brought in from Belgium to pave the roads! youtu.be/R00JSTLw-f0?...

youtu.be

Geology of Paris-Roubaix - When did the Hell of the North break loose?

YouTube video by Geo-Sports - The Geology of Sports Events

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Geology of the Tour de France @geotdf.bsky.social · 07/07/2025

Well, dry, it was occupied by a tundra and a large river, that combined the Rhine, the Meuse, the Scheldt, and the Thames. These flowed towards the Bay of Biscay. Mammoths roamed the banks, and the vast tundras south of the ice caps of Scandinavia.

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Geology of the Tour de France @geotdf.bsky.social · 07/07/2025

OK, so we decided not do skip a GeoTdF year, but this stage is so boring that it's begging for some geo-info! We're riding along the North Sea coast towards Dunquerque. But even as recent as 20.000 years ago, there was no coast here! During the last ice age, the Channel was dry!

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Geology of the Tour de France @geotdf.bsky.social · 05/07/2025

Thanks a lot! We've really enjoyed the past four Tours and explained the geology of cycling races the world over and all year. Last year was a climax. This year there's a cooling down: it was all a hobby between full-time jobs, and those take precedence this year. But we might be back 😎.

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Geology of the Tour de France @geotdf.bsky.social · 04/07/2025

I wish you a fantastic Tour, Ned. Thanks for your interest and support in our off-topic contributions of the last years. We'll be listening and enjoying the commentary of you, David, Peter et al, and everytime you see a rock along the parcours, know that we planted it there especially for you :D

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Geology of the Tour de France @geotdf.bsky.social · 03/07/2025

We’ll go light this year, a detox after four intensive years of Geo-Tour covering 😃. But check out the site, blogs, and clips of last years, most regions are covered!

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