**4. Age of Mazo eruption**

Within the eruptive system of Timanfaya (1730–1736) there are very few volcanic episodes sufficiently documented in historical chronicles to establish their precise spatial and temporal location in order to reconstruct Timanfaya's complete eruptive history. This fact has made it difficult to establish the complex formation sequences of the entire eruptive system. Although some authors have proposed evolutionary sequences that interpret the Timanfaya individual eruptions by analyzing historical information combined with chronostratigraphical studies and geological and geomorphological mapping (eg. [9, 11, 18–21]), there are still uncertainties about when, where and what volcanic processes occurred in each of the multiple eruptive vents and fissures developed during those

**183**

**Figure 9.**

*Timanfaya main fissure are also shown.*

*Syn-Eruptive Lateral Collapse of Monogenetic Volcanoes: The Case of Mazo Volcano…*

been assigned both to Caldera de Los Cuervos [19] and Pico Partido [21].

Our detailed map of lavas around Mazo (**Figure 9**) indicates that its deposits are surrounded, on the west, by lava flows from 1824 eruption and, on the east, by lava flows without direct connection to any emission center but probably coming from later eruptive phases of Pico Partido. Pre-Mazo lava flow, probably coming from Caldera de los Cuervos outcrop to the north of Mazo, partially covered by lapilli. For more information on the possible assignment of Mazo to Timanfaya eruption we have reviewed historical chronicles. The information comes from several

*Lava flows and historical volcanic cones around Mazo volcano. Main normal faults trending parallel to* 

6 years of the 18th century [11]. This is the case of Mazo volcano whose age and

Most authors suggest that Mazo volcano was one of the multiple eruptive fissures of Timanfaya eruption [9, 11, 17, 24–26], while others assume that it was formed during a pre-Timanfaya eruption. Published geological maps include it as a Middle Pleistocene volcano but pointing out the possible existence of an historical emission center in the area due to the very recent aspect of several bombs and scoria [27, 28]. Other authors consider Mazo as an eruption prior to Timanfaya based on the following considerations [19]: 1) a visual recognition of this volcano suggest an old cone due to its color and eroded aspect; 2) paleomagnetic data of Mazo volcano show differences in magnetic parameters (declination and inclination) compared to other Timanfaya's well studied volcanoes; and 3) this volcano is surrounded by lava flows issued by vents from the Timanfaya initial eruptions, previous to Mazo. All these criteria can be discarded if we consider that: 1) the eroded aspect of Mazo is due to the hydrothermal alteration caused by fumarolic activity and remnant heating and gas escape through the DAD; 2) the previously considered as Mazo lava flows are in fact a DAD so paleomagnetic orientations can be nearly uniform in every single block but the declination changes between blocks and from the source [14]; and 3) the origin of lava flows surrounding Mazo is not clear. It is evident that the lava flows emitted by the first vent of Timanfaya (Caldera de Los Cuervos), destroyed the village of Mazo on September 11th [9, 11, 17, 19, 24–26]; however, there is a disagreement on the source of the lava flows that overlie the eastern sector of Mazo, that have

*DOI: http://dx.doi.org/10.5772/intechopen.93882*

eruptive style are quite controversial.

### *Syn-Eruptive Lateral Collapse of Monogenetic Volcanoes: The Case of Mazo Volcano… DOI: http://dx.doi.org/10.5772/intechopen.93882*

6 years of the 18th century [11]. This is the case of Mazo volcano whose age and eruptive style are quite controversial.

Most authors suggest that Mazo volcano was one of the multiple eruptive fissures of Timanfaya eruption [9, 11, 17, 24–26], while others assume that it was formed during a pre-Timanfaya eruption. Published geological maps include it as a Middle Pleistocene volcano but pointing out the possible existence of an historical emission center in the area due to the very recent aspect of several bombs and scoria [27, 28]. Other authors consider Mazo as an eruption prior to Timanfaya based on the following considerations [19]: 1) a visual recognition of this volcano suggest an old cone due to its color and eroded aspect; 2) paleomagnetic data of Mazo volcano show differences in magnetic parameters (declination and inclination) compared to other Timanfaya's well studied volcanoes; and 3) this volcano is surrounded by lava flows issued by vents from the Timanfaya initial eruptions, previous to Mazo.

All these criteria can be discarded if we consider that: 1) the eroded aspect of Mazo is due to the hydrothermal alteration caused by fumarolic activity and remnant heating and gas escape through the DAD; 2) the previously considered as Mazo lava flows are in fact a DAD so paleomagnetic orientations can be nearly uniform in every single block but the declination changes between blocks and from the source [14]; and 3) the origin of lava flows surrounding Mazo is not clear. It is evident that the lava flows emitted by the first vent of Timanfaya (Caldera de Los Cuervos), destroyed the village of Mazo on September 11th [9, 11, 17, 19, 24–26]; however, there is a disagreement on the source of the lava flows that overlie the eastern sector of Mazo, that have been assigned both to Caldera de Los Cuervos [19] and Pico Partido [21].

Our detailed map of lavas around Mazo (**Figure 9**) indicates that its deposits are surrounded, on the west, by lava flows from 1824 eruption and, on the east, by lava flows without direct connection to any emission center but probably coming from later eruptive phases of Pico Partido. Pre-Mazo lava flow, probably coming from Caldera de los Cuervos outcrop to the north of Mazo, partially covered by lapilli.

For more information on the possible assignment of Mazo to Timanfaya eruption we have reviewed historical chronicles. The information comes from several

### **Figure 9.**

*Lava flows and historical volcanic cones around Mazo volcano. Main normal faults trending parallel to Timanfaya main fissure are also shown.*

*Updates in Volcanology – Transdisciplinary Nature of Volcano Science*

sulfur, jarosite, gypsum and anhydrite; 3) a white laminae made of amorphous silica and opal-A. Occasionally, oncoids are composed of Fe-hydroxide coatings, opal-A

*(A) Schematic stratigraphic column of Mazo. (B) Minimum area affected by ash dispersion (oval in gray) from Mazo volcano (in green) based on the location of affected villages (red dots). (C) Cartoons showing the* 

Within the eruptive system of Timanfaya (1730–1736) there are very few volcanic episodes sufficiently documented in historical chronicles to establish their precise spatial and temporal location in order to reconstruct Timanfaya's complete eruptive history. This fact has made it difficult to establish the complex formation sequences of the entire eruptive system. Although some authors have proposed evolutionary sequences that interpret the Timanfaya individual eruptions by analyzing historical information combined with chronostratigraphical studies and geological and geomorphological mapping (eg. [9, 11, 18–21]), there are still uncertainties about when, where and what volcanic processes occurred in each of the multiple eruptive vents and fissures developed during those

**182**

**Figure 8.**

white laminae and yellow laminae.

*main phases of Mazo eruption (see text for explanation).*

**4. Age of Mazo eruption**

sources: 1) the description of the eruption made in 1744 by the priest of Yaiza in his diary (hereinafter CY) (referred in [29]); 2) the data contained in a manuscript with the dossier promoted by the Royal Court of the Canary Islands, which is currently preserved in the General Archive of Simancas (hereinafter MsS) [9, 16]; and 3) notarial and religious data contemporary with the eruptions [25, 30].

It is generally accepted that Timanfaya multiple eruption began at Caldera de Los Cuervos volcano on September 1th, 1730 and lasted until mid-September [9, 11, 19, 21]. After a short rest, on October 10th, 1730 two new eruptive fissures were opened at Caldera de la Rilla and Pico Partido volcanoes forming a NW-SE alignment with Caldera de Los Cuervos (**Figure 1**). Activity in these fissures ended on November 1730 and January 16th, 1731, respectively [30]. On 20th January 1731 a new volcano erupted. Although, some authors assume that this new volcano was Caldera de la Rilla [19], the chronicles say it was located half a quarter of a league (2.4 km) from the previous eruption of Pico Partido [30] and at the destroyed village of Mazo (MsS, letter of February 19th 1731), which was burned and covered by lava flows from Caldera de Los Cuervos volcano on September 11th 1730 (MsS, letter of 17th October 1731 [29], previously to Mazo eruption. There is only one eruptive complex that meets all the conditions, namely: location in the place where the burned village of Mazo was located and distance from the Pico Partido complex of about 2.4 km. That volcano is undoubtedly Mazo. In addition, it is in the continuation of the first volcanic alignment of Timanfaya (**Figure 1**) and have a similar composition (basanitic) of those volcanoes on the NW-SE alignment [18].

Assuming Mazo is the fourth eruptive fissure of Timanfaya some information about the eruption can be extracted from the chronicles. However, it is interesting that there is no reference to this volcanic episode of January 20th in the CY manuscript, which is one of the main sources of information on the eruption. In turn, there is a mention to an eruption starting the 10th of the same month that does not appear in the rest of the consulted documentary sources. Some errors regarding the start dates of some volcanic episodes of the eruption are relatively common in this chronicle [11, 26], probably due to the great spatio-temporal extension of the eruption, to the lack of a continuous monitoring of the eruptive vents, and also to the fact that this manuscript was written 8 years after the ending of the eruption [11], or even to transcription and translation errors of the original document [26].

Even so, if the specific dates are ignored, the sequence of events is similar in all the chronicles consulted. In fact, eruptive activity developed in January 1731, whatever the source consulted or the specific dates, is characterized by the cessation of activity of the volcano opened in the sector of Pico Partido on October 10th, followed by the occurrence of a seismic crisis of considerable intensity whose effects were felt in Gran Canaria Island [9], more than 190 km away, and by the beginning of a new eruption [16, 25, 30].

The narration realized by the Priest of Yaiza for the eruption of January 20th also says: "On the 10th [in place of 20th] of January a mountain raised that the same day crumbled with and incredible crash inside its own crater, and covered the island with stones and ashes. Incandescent currents of lava collapsed onto the malpais up to the sea" [29]. Evidently, CY is describing the sudden collapse of Mazo volcanic cone and the formation of incandescent currents that reached the sea, with a total length of 6 km. The concatenation of later phenomena described in the documentary sources put in evidence that this process gave place to the formation of a high eruptive column that dispersed the pyroclasts over the whole island of Lanzarote (CY, MsS) and part of Fuerteventura (MsS). In mid-February the documentary sources (letter from Ambrosio Cayetano de Ayala; MsS) cite a score of villages in the central part of Lanzarote affected by ash fall [16, 30] (**Figure 8B**). The eruptive event of Mazo volcano lasted only seven days, as CY mentions that this eruption ended on January 27th, 1731.

**185**

*Syn-Eruptive Lateral Collapse of Monogenetic Volcanoes: The Case of Mazo Volcano…*

**5. Evolution of Mazo eruption and causes of the flank collapse**

eruption shifted to strombolian type with emission of scoria (**Figure 8C**).

the base of the cone could have favored the collapse [14, 33–35].

On January 20th 1731, after an intense seismic crisis, Mazo eruption started being the fourth eruptive fissure of Timanfaya. The initial activity was of hawaian type, documented in the outcrops of agglutinates of scoria and clastogenic lavas in the flank of the preserved edifice, and also by the presence of the same type of material integrated in toreva blocks and in some hummocks of the DAD. Later the style of the

The rapid growth of the volcanic cone and a high emission rate may have been determining factors of the flank collapse that took place the same day as the eruption began. In this way, part of the collapse could be favored by accumulation processes in the cone that made it grow extremely quickly, exceeding its stability limit. Thus, once this limit is exceeded, small mass additions can generate debris avalanches [31, 32]. Also, the presence of a huge amount of lava in the crater or at

Doming process does not seem to be the trigger for the collapse, as the faults and fractures affecting the cone are practically parallel and do not follow the fracturing patterns associated with the intrusion and inflation processes [36, 37]. Even so, the geometry of the fractures can vary substantially depending on whether the intrusion is located within, below, or outside a volcanic edifice, and may vary according to the local geology and cause very different consequences [38]. The doming process cannot be ruled out because the original fracture pattern has been obliterated dur-

The existence of fractures that generate a graben structure arranged perpendicular to the direction of collapse, together with the presence of a higher and proximal toreva domain and a hummock domain at the bottom of the collapsed flank, could be related to the existence of basal layers with low viscosity and ductile behavior on the substrate of the volcanic cone, located during movement under the hummock domain [39]. The presence of a basal layer with these characteristics is evidenced in the lava injection processes and squeeze-ups formations in the avalanche sectors subject to compression. In stratovolcanoes, this hypothetical low-viscosity layer belongs to the initial stratigraphic sequence of the stratovolcano and may originally be composed of weak material such as poorly consolidated proximal pyroclasts, coarse-grained tephra sequences, pyroclastic flows, or even blocky lava flows [39]. In monogenetic mafic volcanoes, the existence of basal spatter layers emitted during the initial stages of the eruption and subject to charging processes by accumulation of pyroclasts, has been used to explain rafting processes of volcanic cones. In the case of the flank collapse of a monogenetic edifice like Mazo, this layer may correspond to the spatter emitted during the initial phases, configuring the base of the stratigraphic sequence so that as the height of the volcano increases its weight and so their plasticity increases, thus causing the collapse. Any case, analogue models realized by [2], shows that the deformation of the base is needed for the formation of deep collapses that affect the central area of the cone, as well processes linked to the fracturing of the basement, both through horizontal, oblique

In Mazo, the existence of a well-defined fault in the cone, parallel to a normal fault affecting recent deposits of Timanfaya [40] (**Figure 9**) with a fault displacement of at least 45 m, suggests a structural control. These faults are also parallel to the main eruptive fissure of Timanfaya. A change in the stress field during Mazo eruption is evident if we consider that Mazo is located at the end of the Timanfaya first NW-SE alignment and that Mazo fault is trending parallel to the second ESE-WSW Timanfaya fissure where the volcanic activity was concentrated after Mazo eruption. The intense seismicity previous to Mazo eruption could also be connected

*DOI: http://dx.doi.org/10.5772/intechopen.93882*

ing displacement.

or vertical motions.

*Syn-Eruptive Lateral Collapse of Monogenetic Volcanoes: The Case of Mazo Volcano… DOI: http://dx.doi.org/10.5772/intechopen.93882*
