@geotdf.bsky.social
At @GeoTdF.bsky.social we answer your questions on landscapes and geology cycling races | see Geo-Sports.org for more information!
Ik denk het!
18.10.2025 20:24 β π 0 π 0 π¬ 0 π 0So todayβs winner will have to dig deep for his win. But we advise not to dig too deepβ¦
18.10.2025 08:59 β π 18 π 1 π¬ 1 π 1Critical 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%!
18.10.2025 08:59 β π 9 π 1 π¬ 2 π 0There 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.
18.10.2025 08:59 β π 13 π 2 π¬ 1 π 0It 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.
18.10.2025 08:59 β π 7 π 1 π¬ 1 π 0Geologically, the Col du VAM deposits are best described as a sedimentary mΓ©lange, a poorly sorted, polymict (i.e., with elements of varied composition) and poorly stratified (i.e., layered) agglomerate.
18.10.2025 08:59 β π 7 π 1 π¬ 1 π 0Those 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!
18.10.2025 08:59 β π 7 π 1 π¬ 1 π 0The #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.
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...
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...
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...
So, some background for the start of @lavuelta.bsky.socialβ¦and oddly, the best way to do that is by telling you about the geology of Milano-San Remo π. The first days will be about the Po Plain and the Ligurian Alps! Enjoy!
www.geo-sports.org/2024/geology...
We, too! π
22.08.2025 09:32 β π 2 π 0 π¬ 0 π 0
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?...
And the Swiss Cheese that is the Basque subsurface, and that makes for all the steep climbs!
youtu.be/kCiXOFIMtZU?...
Or the world-famous boundary between the Cretaceous and Tertiary - the end of the dinosaurs - exposed in Zumaia!
youtu.be/5yBTkUd3RWE?...
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?...
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 β23 clip! π
youtu.be/VFXoz3pSPec?...
Oohβ¦I donβt know. And that is a problem π. If I figure it out, Iβll let you know!
27.07.2025 20:00 β π 1 π 0 π¬ 1 π 0
And why is the Jura such a strange, croissant-shaped mountain belt in front of the Alps? Marj will tell you!
youtu.be/CMeyN5AMGAU?...
Racing through the Jura today! In β23 and β24 we made two clips about its geological wonders!
Like dinosaur footprints!
youtu.be/N7hmLLasZrk?...
Clearly, geology raised its ugly head again - literally - to make the Ventoux. And its structure has funny ways in influencing the race π€π€
22.07.2025 09:01 β π 32 π 5 π¬ 0 π 1
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?...
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 NaudΓ© explained where this sharp change comes from!
youtu.be/H7YIk3DnCug?...
Pyrenees! Mine country!
Time for the 2024 story of Metal & Rock!
youtu.be/tImHaE0i9w4?...
While riding over the Cantal volcano π - Europeβs largest, itβs 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?...
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?...
A neandethal on a bike on the ice
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.
07.07.2025 14:04 β π 20 π 2 π¬ 1 π 1
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?...
