Geology of the Tour de France

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@NostraHoekstra @vismaleaseabike @ParisNice Ah, is that where I was racing! It hurt so much that it could’ve been Mars for all I knew.

@geotdf @vismaleaseabike @ParisNice Tirreno-Adriatico, you mean ;)

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 😎 🦖 @vismaleaseabike @ParisNice

The #TourofHolland gives us the opportunity to introduce the geologically most puzzling mountain of Europe: the @ColDuVAMdrenthe! The Dutch province of Drenthe is world-famous for Pleistocene ice-age geology. It is scattered with large ice age erratics: enormous blocks of gneiss and granite that were transported from Sweden and Finland by giant glaciers (check out @Hunebedcentrum). 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! 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. 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. 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. 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%! So today’s winner will have to dig deep for his win. But we advise not to dig too deep...

During the Holland Tour, the peloton will pass the Geulhemerberg! See @MelanieDuring’s clip about the treasures hidden along the climb! youtube.com/watch?v=ZkM73H…

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! youtube.com/watch?v=IZSZfQ…

We’ve had a year off, but we can’t let the Holland Tour go by unnoticed, can we? A stage through the polder of the Alblasserwaard today. Check out out blog of its history: geo-sports.org/2024/stage-2-t…

@pgw6211 @nedboulting If @nedboulting could use us, I’m sure he knows where to find us. It would be our pleasure.

@nedboulting @geotdf perhaps some rock facts too?

@lindaschaos We are on Bluesky, same name!

@geotdf I've just liked you on FB. Any chance you may join Bluesky? It's like Twitter used to be - nice 😀

After several fantastic years with all of you, dear geo-cycling enthusiasts, we have decided to stop posting on X. Twitter was once a great, non-political platform where geeks could exchange about their hobbies. By now, the place has gone dark, and we are no longer willing to pay the lunatic who runs it. And without paying, we won’t reach you. We will continue on all other platforms, check out geo-sports.org for the links! We’re sorry to leave, and we thank you for your interest in GeoTdF! ❤️❤️

Today is the day of the Dutch Championships Headwind Cycling, where pro riders get beaten by the mailman! It will be a mild edition, with only a 6-7 Bft westerly wind, but the race parcours is chosen such that there is zero protection: the 9 km long Oosterschelde dam! A dam with a history. The race will be held in Zeeland, a province in the SW of the Netherlands. Zeeland is an amalgamation of islands in an estuary, where the Meuse, Rhine, and Scheldt rivers meet the North Sea. And with the Dutch hobby of making polders, this land is especially vulnerable for floods. On February 1st, 1953, disaster struck. A storm surge led to multiple dike breaches, and an area of 150.000 hectare (370.000 acres) flooded. Nearly 2000 people drowned that night. 47000 cattle and 140000 poultry died. This was not the first flood, but it was the worst. Following this disaster, the 'deltaworks' started: the inlets of the Zeeland estuary were dammed, dykes were raised. The project took decades and shortened the Dutch coastline by 700 km. All but one inlet are now dammed: only the Westerschelde, that leads to the Antwerp harbor, is still open. While the project became an enormous engineering success, it had ecological downsides. The dammed inlets turned from brackish to fresh water, affecting biodiversity. The final dam, of the Oosterschelde, is therefore contains open partitions that only during storms are shut. For the riders today, this is bad news. When the partitions are up, they provide some shelter to the wind. But during today's storm, they'll be down. Perfect conditions for some suffering. The organization is well prepared: behind the finish line, there is a puke station with plenty of buckets 😂.

@GiorgioGiovane Gonna be epic, I’m sure!

@geotdf Yes, I phrases my tweet badly. I hope you get the race this weekend!

Headwind Cycling Championships declared for Saturday! (Last time I remember this happening they were then cancelled due to wind!)

We kriehen sturm! 🌬️ Forget the Tour de France: the Dutch Headwind Cycling Championships will be held on Dec 7! An 8 Bft storm will blow on the 9 km long Oosterschelde dam, and 300 racers will battle it on city bikes. We'll be there with the Geology of Shit Weather! zeeland.com/en/live-work/n…

For the many of you that are leaving X, but still would like to stay up to date the Geology of the Tour de France and other cycling races: follow us on all major socials. See geo-sports.org for links!

@Beatever No, but it sure looks nice!

@geotdf Those are not the scientific colours?

What a great idea! 😍😃

@Riou_du_Cosquer Groix Island is a blueschist complex! That gets geologists totally fired up, because it means you live on rocks that formed at 40 km depth in an ancient sudbuction zone! You know, where those tsunami-forming earthquakes occur. So ok, we'll cover Groix in our Twitter-reports :D.

@geotdf You will ! Best from Brittany near the Groix Island.

Normandy, Brittany and Mont Ventoux...just as we ran out of funding for clips 😭. Ow man, there's so much to tell there!

@nedboulting 😢 all good things come to an end?