Fernando Escartín commentary
Mid-mountain. Favourable stage for breakaways. The 2nd category Garbí climb may lead to the formation of a group that will fight for victory, but this will all depend on how good the breakaway is. By this point, there will already be around 15 riders who stand out in the general classification and we will know who has a real chance of winning La Vuelta.
What the mountains are hiding
Vila-real - Sagunt
The diagram shows how the route crosses the coastal mountain ranges of Espadán and Calderona, with the Palancia River flowing between them. They consist of rocks from the Triassic Period (around 250 million years old, shown in violet) and the Cretaceous Period (shown in green), all of them very deformed during the Alpine Orogeny (40-20 million years ago). In the valleys and coastal plains, the entire territory is made up of grey Quaternary sediments.
The world's glaciers have spent the Quaternary Period (the last 2.5 million years) going through several periods of growth and fusion, depending on climate changes, either removing or returning water to the oceans. This is why the sea levels have not stopped rising and falling and the Plana de Castellón is the result of these climate and sea level changes.
La Plana is formed by different types of sediments: the river sediments are formed mainly by floods, active or preserved beaches, deltas and dunes. All of this allows geologists to reconstruct how the sea levels have risen and fallen over the last several thousand years and, thus, associate them to climate changes.
As in other stages, coastal plains take the peloton to the mountain ranges and broken terrains. First, the Espadán Mountain Range, which is made up of ancient materials (around 250 million years old), with numerous folds and faults of alpine origin that formed around 30 million years ago and were later remodelled by the erosion produced by rivers and underground water.
In the Vall d'Uixó, on the slopes of this mountain range, is one of the region's most interesting geological spots, the caves of San José. These consist of one of the largest karst gallery networks in the Autonomous Community of Valencia, and the stage route passes over one of these immense hollows on several occasions. Inside them is the longest navigable subterranean river in Europe. These galleries were formed when the carbonate (mineral that limestone rocks are made of) dissolved, which resulted in truly beautiful landscapes.
We then go through the Calderona Mountain Range, a natural park located between the borders of Castellón and Valencia. With similar origins to the Espadán Mountain Range, the rocks of Calderona are cut by faults that have been moulded by erosion, giving them and the ravines through which the riders will pedal in these final stage climbs their molar shapes.
Two important faults are those of Castell and Garbi, which create an ideal relief for defensive purposes, which is why its 11th century inhabitants settled in the Serra Castle.
Lastly, the stage will end in the Roman city of Sagunt, in the mouth of the Palanca River.
Stage Term: Karst
A karst is a type of relief where the dissolution of rocks has resulted in the creation of caves and chasms inside the earth (endokarst) and sinkholes, limestone pavements and poljes on the surface (exokarst).
Limestone and dolomite stones are generally formed in marine environments and consist of carbonate minerals (calcite and dolomite) that easily dissolve in acidic water. Like everything related with geology, this an extremely slow process, but over millions of years, these rocks eventually dissolve inside, resulting in a karst.
Jersey wearers after the stage 4
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