Volcanic remains in the Basque Country: The geology of volcanic origin in the Basque Country: “There is no risk of magmatic activity in the Basque Country” | Radio Bilbao

The five most significant points in this field are located in Bizkaia and Gipuzkoa

1. The chair of Elgoibar
2. The dikes of Eibar
3. Soraluze pillow lavas
4. The Karakate mountain
5. The lava flow of Meñakoz beach

The chair of Elgoibar

It is part of a set of sills that emerge in the vicinity of the town. They are sedimentary rocks of the Vraconian age, below the bulk of the volcanic formations that form the volcanic complex in this sector. The scientific interest (petrological and mineralogical) of the Elgoibar sill is unquestionable. Is formed by relatively fresh igneous rocks, which preserve their primary mineralogy practically intact, which constitutes an exceptional case in the rocks of the complex volcanic of Cretaceous age, whose mineralogy is strongly transformed by a intense hydrothermal metamorphism.

Its mineralogical and geochemical study will allow obtain important data on Cretaceous volcanism and nature of the source mantle implicated its genesis. It will also allow you to obtain valuable informationtion on magmatic differentiation processes controlled by frac crystallizationionized that develop in magmas of mantle origin. But in addition, the Elgoibar chair constitutes an excellent didactic example of this type of basic-ultrabasic intrusions, since it offers the possibility of discussing aspects so importantimportant factors of geology such as the nature of magmas of mantleic origin, the differentiation processes responsible for their compositional diversification, the causes the rise and location of magmas, etc.

Dikes of Eibar

In the outcrop located in the Altzubarren neighborhood there is an underwater volcanic sequence made up of lava and volcanoclastic products. The dikes are the peculiar element of this volcanic outcrop, but the whole sequencecia, that is, pillow lavas, breccias and stratified tuffs, constitutes a typical deposit of a relatively shallow underwater volcanism, possibly emitted in an eruption Strombolian type. The observed volcanic sequence suggests that the first eruptionsThe nests developed in an explosive, magmatic and / or phreatomagmatic way, forming the Pyroclastic deposits (breccias and tuffs). Later, the basaltic magma, previously desGasified in explosive eruptions, it is emitted on the ocean floor in a tran caraway, effusive, and with low emission rates, forming the wash of cushioned lavas

Soraluze Padded Washes

In the surroundings of the Gipuzkoan town of Soraluze, one of the most powerful sequences of the underwater volcanic complex emerges. Numerous pillow lava flows appear interspersed with trachitics, pyroclastic deposits, pillow breccias and other volcanoclastic formations. The volcanic sequence is crossed by numerous sinvolcanic dikes and sills. All the
volcanic sequence outcrops on the road that connects Soraluze to the top of Mount Karakate, passing through the neighborhood of San Andrés, but stand out, among others, the outcropslocated on the outskirts of this town, on the promenade that connects the neighborhoods of Zeleta and Agarre Bolu, passing through Arkaitz.

Trachytes of Mount Karakate

The trachytic rock outcrop located between the top of Mount Karakate and the cross del Muneta allows observing the characteristics of the lavas and trachytic breccias that constitute the acid pole of the alkaline volcanic series of Cretaceous age of the CuenBasque-Cantabrian ca, which are scarcely represented in the deposits of the volcanic complex. They are formed by fractional crystallization of basaltic magmas, and reveal the stagnation and differentiation of basaltic magmas in shallow magmatic chambers. But also, the road that from Soraluze ascends to the top of Mount Karakate offers an exceptional geological section of the north flank of the volcanic complex in its paryou more powerful. Practically all the products are represented in this section volcanoes that form the Cretaceous-age submarine volcanic complex of the Basin Basque Cantabrian

Lava flow of the Cala de Meñakotz

In Meñakotz there is a stream of cushioned lavas, named for their appearance, which originate in volcanic eruptions that take place under water. It is accessed from the BI-2122 road between the towns of Sopelana and Barrika, take the detour that leads to the Meñakotz cove. Go down the track and go south-west along the pebble beach to the cape. The lavas found at the western end of Meñakoz beach form one of the most representative lava flows of the Upper Cretaceous age of the Basque-Cantabrian Basin. This outcrop stands out, above all, for the spectacular lava flow (pillow-lavas) exposed on the cliff. However, the volcanic facies that emerge in its prolongation in the intertidal zone are equally interesting and, some of them, exceptional.

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