When most people think of Spain, they tend to not think of volcanoes.
Yet, the country contains several active volcanoes, of which two are on the Spanish Mainland.
One of these volcanoes is located south of Madrid, and produced volcanic activity in
the 19th century.
The volcano I am referring to is the Calatrava Volcanic field, which has been intermittently
erupting for several million years.
As such, it is only a matter of time before this volcano erupts again.
This video covers the recent eruptions from this volcano, and states the general hazard
which it poses in the future.
The Calatrava volcanic field is centered about 190 kilometers south of Madrid near the town
of Ciudad Real.
This field consists of more than 360 volcanic vents spread out over an area of about 5,000
square kilometers.
On screen, I have loosely outlined the boundary of this volcanic complex.
Each of these numerous vents are monogenetic, which means they erupt once and then never
erupt again.
The reason why this volcanic field exists is quite unusual.
To the south of Spain there is a boundary between two tectonic plates.
However, there is also a rift zone, which is slowly spreading the crust apart.
This movement of this rift zone has created numerous parallel faults in central Spain
as an extension of this system.
These faults allow magma to travel upwards and erupt onto the surface, thus forming the
overall volcanic field.
The Calatrava volcanic field has been erupting for a very long time, since about 8.7 million
years ago.
Since then, eruptions have occurred every few tens of thousands of years.
These eruptions occurred in a nonuniform assortment throughout the area, forming two different
types of volcanic vents.
The two types of vents formed from various eruptions are cinder cones and volcanic explosion
craters called "maars".
One of the most interesting vents in this volcanic field is Laguna de Fuentillejo.
This harmless looking lake formed as the result of a highly explosive eruption.
It represents the center of a 1 kilometer wide, and 55 meter deep explosion crater.
It formed when a volume of magma rose towards the surface through the crust.
Eventually, this magma heated a region of nearby groundwater beneath the surface, thus
causing it to flash to steam.
Eventually, this steam expanded in volume until a large explosion occurred.
This eruption blew chunks of rock in a several kilometer radius, and created a series of
short distance pyroclastic flows.
Despite the size of the crater formed by this eruption, it would have been classified as
a small eruption, only rating on the volcanic explosivity index as a 2.
The most common type of volcanic vent in this field are called cinder cones.
Cinder cones form through mildly explosive eruptions which eject large volumes of lava
and ash.
The small explosions during these eruptions cause ash to fall close to the erupting vent,
thus forming a gray cylindrical volcanic cone.
The most recent volcanic eruption occurred in 3600 BC, and formed one of these cinder
cones.
Although it has since been heavily eroded, this eruption formed a 600 meter wide and
90 meter tall cone called Volcan Columba.
Since this eruption, no additional eruptions have occurred.
With this being said, there was volcanic activity in the 18th and 19th centuries.
During that time, a section of ground opened and started to emit large amounts of volcanic
gasses.
These emitted gasses occurred from volcanic fumaroles, hinting at magma not far beneath
the surface.
So, will this volcanic field erupt again?
To this question I say yes, and I am certain that it will erupt again.
Since this volcanic field has been active for about 9 million years, it is unlikely
to quit in my lifetime.
If another eruption was to occur, it would either create a new cinder cone or volcanic
explosion crater.
A cinder cone eruption would be less deadly, as the main threat would be slow moving flows
of lava which could travel up to 5 kilometers away.
If a maar forming eruption was to occur, it would create pyroclastic flows that would
travel up to 8 kilometers away.
If a future eruption was to occur, it would be almost certainly preceded by a swarm of
strong earthquakes.
Using the US Geological survey method of rating volcanoes, the Calatrava volcanic field would
be classified on the upper end of the moderate threat category.
The odds of it producing an eruption in any given year are about 1 in 24,000.
I hope that you enjoyed this video!
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