, The Canary Islands are part of the Canary Island Seamount Province (CISP) that consists of more than 100 volcanic seamounts. They are part of a hotspot track that extends across the African plate with a very general northeast-southwest age progression. The track begins near Essaouira seamount (68 Ma) and terminates near El Hierro and La Palma (0.4 Ma). It is approximately 1300 kms long and 350 kms wide and trends parallel to the African continental margin. Presently, there is a submarine eruption occurring south of El Age vs distance for Canary and Hawaiian Islands (Carracedo Hierro, extending the track. et al., 1998)

The track is not well defined; the distribution of “oldest” ages of the seamounts is varies considerably and the seamount trend is parallel to paleomagnetic anomaly M25 (142 Ma) in the Atlantic seafloor. Ar40/Ar39 data indicate a physical connection between the mantle plume and the moving plate. The most probable model for the plume is shallow mantle upwelling beneath the Atlantic basin that generated Island age trend and overlap of the island aprons (Guillou et al., 2004) recurrent melting from the Late Jurassic to Recent (van den Bogaard, 2013). This is very different than the fixed-plume, deep source, high production Hawaii-Emperor hotspot track. A deep fixed- plume mantle upwelling would have generated a track that trends more east-west.

Herman (1975) related the magmatism to a propagating fracture system from the Atlas mountains (trans-Agadir fault) that created a conduit through the lithosphere but this model has significant evidence against it (Guillou et al., 2004). A local extensional ridge may have been active during the Cenozoic but there is little evidence of this either (Fuster, 1975). Arana and Ortiz (1986) suggested compression uplifted tectonic blocks that became the islands and magmatism occurred during relaxation; again, these is little evidence for this model. The mantle plume Oldest ages of seamounts and islands from van den Bogaard (2013). Includes plate motion vector from UNAVCO model convection cell may move horizonally beneath the lithosphere toward the craton, resulting in the long-term volcanism observed on several of the Canary islands (up to 23 my for Fuerteventura). This model was proposed by Geldmacher and others (2005) and Gurenko and others (2006)

When the age of just the islands is considered, the track is more defined. The emergent islands extend 490 kms and increase in age toward Africa (east). Islands and seamounts of the Canary Islands

(Carracedo and Perez-Torrado, 2013) Ocean Island volcanoes go through a phase of construction followed by destruction; during the destructive phase erosion and mass wasting exceeds volcanic growth and eventually the island is eroded to sea level. volcano represents the peak of the construction phase in the Canary Islands (Carracedo and Perez-Torrado, 2013). Subsidence of the Canary islands is much slower than the Hawaiian islands, this is probably due to the age and thickness of the underlaying lithosphere (Jurassic).

Tenerife consists of three main shield volcanoes (Roque del Conde massif, Teno and Anaga volcanoes) with compositions ranging from basanites to phonolites. The eruptive history of Tenerife is similar to other ocean islands, growth of main shield volcanoes followed by an eruptive quiescence and then rejuvenation volcanism.

The first of the main shield volcanoes developed in central Tenerife (Roque del Conde massif). Erosion and possibly landslides removed the northern flank of the shield. 40Ar/39Ar and K/Ar dates between 11.6 and 8.9 Ma have been obtained (Guillou et al., 2004). The Teno shield formed approximately 6 Ma along the western side of the Central Shield which had entered a quiescence phase. Radiometric ages indicate growth of the Teno shield occurred between 6.1 and 5.2 Ma (Guillou et al., 2004; Longpre et al., 2009). Anaga shield, to the northeast, developed between 4.9 and 4.0 Ma (Guillou et al., 2004; Walter et al., 2005). This series is frequently referred to as the Old Basaltic Series. The rejuvenation phase of Tenerife is represented by Las Cañadas Volcano in the island center starting around 3.5 Ma (Ancochea et al., 1990; 1999; Huertas et al., 2002). The Las Cañadas Volcano is a composite stratovolcano composed of the mafic to intermediate lower group (3.5 – 2.2 Ma) and three felsic cycles of the upper group, the Ucanca (1.59 – 1.18 Ma), Guajara (0.85 – 0.65), and Diego Hernandez (0.37 – 0.175 Ma). Each of these upper group cycles ended with a caldera collapse after a felsic pyroclastic eruption (Ablay et al., 1998). These collapse episodes formed Las Canadas caldera.

The Teide Volcanic Complex is the most recent phase of the Las Cañadas Volcano within the caldera. This renewed volcanic activity started around 175 ka. Tiede, Pico Viejo and smaller volcanic vents, including Montana Blanca, produced substantial subplinian phonolitic eruptions around 2 ka (Ablay et al., 1995; 1998).

Concurrently, during the past 3 my, rift zones developed to the northwest, northeast and south. The rift zones produced abundant basaltic fissural eruptions and Teide Volcanic Complex produced central felsic magma.

Recent eruptions (Teide and Pico Viejo stratocones) are in the northwest and northeast rift zones. These eruptive centers may have helped trigger the lateral collapse of the northern flank of Las Cañadas Caldera around 170 ka. The central volcano experienced progressively differentiated magmas (Carracedo et al., 2007). There have been four recorded volcanic eruptions on Tenerife; in 1704 Arafo, Fasnia and Siete Fuentes volcanoes erupted simultaneously, in 1706 Travejo erupted and a lava flow buried the city of Garachio, in 1798 Pico Viejo erupted and the most recent eruption was in 1909 when the Chinyero cinder cone formed Location and ages of landslides (Mason et al., 2007) along the northwest rift. Teide volcano is the third highest volcano on earth (3,718 m above sea level, >7 km high). Presently, the volcanic hazard on Tenerife is considered moderate because of the low frequency and modest explosivity (Carracedo et al., 2007).

A GPS array was installed in 2004 due to seismic-volcanic activity around Teide volcano. Between 2004 and 2009 no significant crustal deformation was identified.

A more serious hazard associated with these volcanic islands are submarine collapse events that trigger tsunamis. Landslides on the flanks of volcanic islands generally take two forms, debris avalanches and slumps. A debris avalanche is relatively thin (0.4 to 2 kms thick) with a distinct headwall and a distal deposit of blocky debris. These are rapid, high-energy events. Slumps tend to be gradual down-slope movements of a thick (up to 10 kms) coherent block. Most of the mass wasting events on the Canary Islands are debris avalanches with slumps only identified on El Hierro. Most landslide activity is limited to the volcanically active islands, Tenerife, La Palma, and El Hierro. On average, one landslide occurs every 100,000 years, the most recent occurred on El Hierro approximately 15,000 years ago (Mason et al., 2007). Las Cañadas Caldera (Carracedo and Perez-Torrado, 2013)

Harris and others (2011) reported evidence of an ancient collapse event on the southeastern flank of Cañadas volcano. The landslide deposit was up to 50 meters thick and extended over a 90 km2 area. The deposit consists of debris avalanche material with an unsorted matrix. The age of this event has been dated at 733±3 Ka. This landslide event resulted in a gap in the rim of the caldera which subsequently channeled pyroclastic flows to the southeast.

Recent volcanism on Tenerife (Carracedo et al, 2007)

Carracedo (1994) noted that the rift zones contribute to the mass wasting of the volcanic islands. Gravitational stress, generated by the growth of the volcanic edifices, contribute to the instability and seismicity, associated with magma movement, can trigger mass wasting events. Landslides, enhanced by subsequent erosion, produced many large horseshoe-type scarps and calderas in the Canary Islands. Other hot spot volcanic chains, such as the Hawaiian Islands, experience rapid subsidence after the construction phase ends. The Canary Islands do not subside, possibly due to the thick and old (Jurassic) lithosphere they form on. These ocean islands remain elevated for a long time (20 my old volcanics are observed on the islands) and are more susceptible to gravitational collapse.

Gee and others (2001) identified four different landslides on El Hierro. The most recent, El Golfo (SW flank) occurred 15 ka. This is the best described landslide of the Canary Islands. The El Julan landslide (SW flank) occurred >200 ka and is characterized by gravitational slumping. Las Playas (145-176 ka) and San Andres (older) both occurred on the SE. Ward and Day (2001) use geological evidence that suggests that during a future eruption Cubre Vieja Volcano on the island of La Palma may trigger failure of the west flank involving 150 to 500 km3 of rock. They model a tsunami front with a velocity of 100 m/s that would produce a 10-25 m wave on the eastern Americas. The predicted travel time to Florida is approximately 9 hours.

Ground water is mined through a large network of infiltration galleries excavated throughout Tenerife. Ground water galleries (Carracedo, 19994)

Geologic Time Scale

http://www.geosociety.org/science/timescale/

Wednesday, March 12th We arrived in the afternoon, after an exhausting day-long flight from Seattle with layovers in New York and Barcelona. A short bus ride from the Santa Cruz de Tererife airport got us to the bus station in Puerta de la Cruz, on the north shore of the island, walking distance from our hotel. We struggled to pack light for a seven month trip, but with computers, camera equipment, hiking gear and “nice” clothes, it wasn’t easy nor effective. We were both lugging about 45 lbs of luggage. Our walk to the hotel convinced me that Veena was probably right; I should have invested in a rolling duffle instead of one that had to be carried.

The geography of Tererife (and other Canary Islands) reminded me of the Hawaiian archipelago; lush tropical flora on young, dramatic, volcanic terrain but culturally it is distinctly European. As we flew into the airport and during our bus ride to Puerta de la Cruz, Teide volcano dominated the skyline to the southwest. The volcano has a beautiful steep, symmetrical cone that, at this time of year, is coated with a thin layer of snow and ice. Although there is little to provide scale, it looms large. At 3,718 meters (12,198 ft) in elevation and 24,600 ft from the ocean floor, it is the third only to Mauna Kea and Mauna Loa in total height for a volcanic island. The smooth, un-eroded slopes indicate the dormant volcano is still active. Teide is one of 16 Decade Volcanoes identified by the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) as being particularly hazardous due to their eruptive history and proximity to populated areas (Mt. Rainier is another…).

Puerta de la Cruz is located on intermediate to basic volcanics that were erupted from the northeastern rift during the Pleistocene (>33,000 ybp). The volcanic hazards of La Orotava valley are relatively low, the last eruption from the northwest rift zone was 11,000 ybp.

Puetra de la Cruz was founded in the early 16th century at a port. Originally a fishing village dependent on La Orotava population center, it became the principle port on the island in May, 1706 when the port of Garachico, 15 kms to the west, was destroyed by a volcanic eruption. The 1706 eruption, one of the most recent eruption on Tenerife, originated along the northwest rift zone and, over several weeks, filled the old bay with lava. The old harbor of Puerta de la Cruz is small but well protected by an extensive sea wall. Throughout the city, (vesicular) dark volcanic rock is used as a construction rock.

Friday, March 14th The island of La Gomera is about 20 kms west of Tenerife. We took an early morning bus from Puerto de la Cruz to Los Christianos on the island’s south coast and a ferry from Los Christianos to San Sabastian, La Gomera. The ferry crossing took about 45 minutes. San Sabastian is the harbor that Christopher Columbus got his final provisions prior to sailing west in September, 1492. This small harbor is still used as a departure point for trans-Atlantic crossings. The island of La Gomera is relatively small (370 km2) and circular. The central peak, Alto de Garajonay, is 1,487 meters high and located in Parque de Nacional Garajonay (Garajonay National Park). A cloud forest (laurel rain forest) exists at high elevations, fed by clouds of the trade winds. The Laurissva forests are also found on La Palma, Tenerife and Gran Canaria; they flourish on the north side of the islands, facing the trade winds. Even though precipitation is rare, the condensation due to cloud movement through the forests provide considerable moisture.

The volcanoes on this island are old, extinct, and highly dissected; deep ravines, barrancos, cut the flanks of the island in a radial pattern. During the Miocene (9.4 – 8.0 Ma) basaltic shield volcanism created the core of the island with a very late phonolitic and trachytic phase identified at a central crater in the northern part of the island. Pliocene basalt flows persisted until volcanic activity ceased on La Gomera 4.0 Ma (other than some minor basalt flows around 1.9 Ma) and since that time the island has undergone intensive erosion by gradual fluvial processes and secondary failures (Llanes et al., 2009).

Several volcanic plugs can be found on La Gomera, the most spectacular (and famous) being Roque de Agando. This relatively resistive rock emerged as the less resistant basalts and pyroclastics were eroded from around it. It now stands 1,246 meters high. Other plugs include Roque Roque de Agando, a volcanic plug Ojila and Roque Zarcita.

Saturday, March 15th Pico Viejo, located a couple kilometers to the southwest of Teide produced several basaltic lava flows. An eruption around 27,000 ybp generated a flow Map of the Cueva de Viento lava tube system. Colors represent different levels. that created a series of lava tubes, Cueva del Viento (Cave of the Wind), south of Icod. Our tour guide was Francisco Manuel Mesa Luis, a biologist.

These lava had very low viscosity, producing pahoehoe flows. These flows have been identified as Pico Viejo’s first eruptive phase. The Cueva del Viento-Sobrado tube complex is the largest in the European Union. It consists of three superimposed levels, 1 (lowest) to 3 (highest) and has a total of 18 kms of tubes (4th longest in the world). The caves also contain 190 known species and vertebrate fossils of extinct animals such as a giant rat (Canariomys bravoi) and giant lizard (Lacerta goliath). Mummified remains of the , the indigenous people of the Canary Islands, were also found.

A later Aa flow that originated in Pico Viejo around 1,800 ybp covered part of the earlier pahoehoe flow and created a deep and wide channel down the flanks of Tenerife to the sea. This flow was much cooler, more viscous and contained significant obsidian.

The slope of the lava tubes is approximately 20°, suggesting a very rapid flow rate (estimated at 20- 30 kms/hr). The magma was extremely fluid, probably having a temperature of around 1,100 °C. The tubes have well-developed terraces that are interpreted as persistent lava levels as the level dropped in steps, a sequence of terraces formed due to marginal cooling. It is hard to imagine the lava level in the tube remaining constant over an extended period of time because this would a constant emission rate. The terraces are probably Terraces in the lava tube also due to cooler, more viscous lava flowing as the level dropped (and discharge rate decreased) and this “sticky” lava clung to the margins creating the terraces in less time. It would be interesting to see if the terraces had a slightly different mineral or chemical composition with height.

The superposition of the tubes within the system is interpreted as successive flows that built on top of each other with their own network of lava tubes. At some locations the upper, active tube collapsed into the lower tube and changing the lava drainage. This created passages between the three levels of the system. The flow of hot lava on top of an older flow that may not have been completely cool, would have contributed to the weakening of the lower “roof”. Each meter depth of basaltic lava would have produced a pressure of 2800 kg/m2 and these flows were up to 10 m thick. This would put a lot of pressure on the roof separating the flows.

Lava drip structures and lava “stalagmites” are found within the tubes. These may have been created by younger lava flows that seeped into the older tubes. The roof of a lava tube is far from air-tight, there are Lava drips on the roof of a lava tube. abundant fractures that allow gas to escape. Again, geochemical data may be able to fingerprint the source of the lava.

There seem to be two mechanisms for forming lava tubes, roofing of a small lava channel and coalescing of pahoehoe flow “toes”. Large lava tubes, like the one at Cueva del Viento, form through the latter process. Based on observations in Hawaii, during pahoehoe eruptions, lava continues to flow through pahoehoe toes in the center of the flow. This continuous flow of hot lava erodes (melts) the walls between toes and the flow coalesces to form a central conduit, the lava tube (Rowland and Walker, 1990). Lava tubes are thermally very efficient, lava within a tube only loses about 1 °C per kilometer. The tube system probably remains very ductile as the hot lava continues to flow, expanding and contracting as the flow increases and decreases.

Gas that exsolves from the lava escapes through cracks in the tube or skylights. Skylights are places where the roof of the tube has collapsed, exposing the lava.

Similar to rivers, when the slope decreases and flow slows, the cross-sectional area must be greater. In these locations the flow grows by inflation as well as spreading laterally. A flow can inflate from <1 m to greater than 10 m (Walker, 1991; Hon and Kauahikaua, 1991).

Sunday, March 16th We drove our rental car up to Teide National Park home of 3,719 m Teide and 3,135 m Pico Viejo volcanoes. The base level of the park is around 2,000 m. This is one of the most visited national parks in the world, receiving 2.8 million visitors annually. Road TF-21 takes you from Puerto de la Cruz up to the park in about 31 kms. The road ascends along the collaped northern flank of the original Las Cañadas Volcano (LCV); there were at least three different debris avalanches that travelled north and left a semi-circular head scarp that was subsequently partially filled by Teide and Pico Viejo. The head scarp appears to coincide with the LCV collapse structures. The Roques de Garcia slide occurred over 600 ka, the Orotava slide occurred between 690 and 540 ka, and the Icod debris avalanche occurred between 170 and 150 ka. Susequent lava flows have partially covered the avalanche slope.

After a brief stop at the visitor center at the enterence to the park, we headed to Minas de San Jose, a few kilometers up the road. The landscape consists of ignimbrite and lavas covered with light-colored pumice lapilli. The dune-like lapilli field is probably depositional and not actually wind deposits due to the coarse-grained nature of the material. The turbulance generated by the eruption probably threw these pyroclastics into their present undulating configuration.

We continued southwest to Roques de Garcia and took a 1.5 hr hike (trail 3) around the feature. These outcrops are interpreted as resistent remnants of the ancient debris avalaches that now extend up through the later lava flows that have eminated frim Pico Viejo and Teide. The outcops have near-vertical dark dikes that may have probably baked and hardened the adjacent agglomerate/volcanic breccia, making it more resistent to erosional forces. A pahoehoe flow down the south flank of Pico Viejo and past the Roques de Garcia. consists of porphyritic phonolite. The phenocrysts are probably alkali feldspar or feldspathoid. Both the pahoehoe and adjacent aa flow has been mapped as intermediate in composition by Ablay and others (1998).

Eruptions of Teide and Pico Viejo produced intermediate and felsic volcanics during four primary episodes (Ablay, 1997) and each of these episodes ended with phonolitic eruptions and collapse of the active vent. The first episode was the most voluminous, intermediate lava created Teide and part of Pico Viejo and culminatd with felsic eruptions on Teide’s flanks, including Montaña Blanca. The second episode produced a sequence of increasingly felsic lavas and ended with the first summit collapse of Pico Viejo and ponding of intermediate lavas. The third episode involved Teide once again. There were central vent eruptions of hybrid lavas, again ending with collapse of Teide. The final phase involved phonolitic eruptions primarily from Montana Blanca. Ablay and others (1998) used geochemistry to determine that the intermediate-felsic volcanics of the Teide and Pico Viejo evolved seperately other than the earliest Pico Veijo eruption which may have been the product of a satellite vent of the Teide magmatic system.

The parental basanites evolved in the lower crust and upper mantle (6 - 12 kbar). Teide chamber appears to have been relatively shallow, approximately 1.5 kbar pressure while the Pico Viejo phonolites developed in a separate shallow chamber, approximately 1 kbar pressure (Ablay et al., 1998).

Phonolites are extrusive (syenite & monzosyenite

equivalent) with abundant alkali (N2O, K2O) producing alkali feldspar (usually sanidine or anorthoclase), alkali pyroxenes (usually aegirine-augite), alkali amphiboles, and, since the rock is undersaturated with respect to silica, Las Canadas Caldera (LCC), Teide (T), feldspathoids (nepheline and leucite). The feldspathoids Pico Viejo (PV), Montana Blanca (MB) from Ablay and others (1998).

are common phenocrysts. Phonolites are frequently associated with (continental) rift mamagatism and evolve from crystal fractionation of silica undersaturated basanite magmas.

Although phonolites are usually considered to have a relatively low silica content, in the case of the Teide and Pico Viejo phonolites, the extremely high concentration of the alkalis result in the silica undersaturation (and formation of feldspathoids); the weight percent of silica in the various phonolites range from 40 to over 60%. The evolution of the phonolites from the parent mafic basanite can be seen in the plot by Ablay and others (1998). Fractional crystallization of mafic minerals resulted in a magma enriched in silica as well as Na2O and K2O. These are really unusual volcanic rocks – particularly since they are found on an ocean island and not in a continental rift. Composition of Peide and pico Viejo From Roques de Garcia we drove west and turned onto phonolites from Ablay and others (1998). TF-38, crossing an extensive intermediate lava flow that emanated from Pico Viejo in June, 1798, the last eruption within the park. The lava came from a vent on the south side of Pico Viejo (Old Peak) known as Las Narices del Teide (The Nostrils of Teide). These vents are clearly seen on the flank of Pico Viejo. The eruption started along a 700 m fissure with gas and pyroclastics being ejected 1000 m into the air and lava flowing from the bottom of the fissure. This eruption lasted 92 days and produced the “badlands” (malpaises) in the western 2 part of the park. (5 km ) We left the park on TF-38, Las Narices del Teide on Pico Viejo. headed Chio and then over the pass on TF-82 (highway was still under construction), through Icod and back to Puerto de la Cruz.

Monday, March 17th Back to National Park in the rental car. We headed up through thick clouds but were above the layer by the time we entered the park, it was sunny all day at elevation. Our first top after the visitor center at El Portillo (the portal) was a short hike (trail 14) around Alto de Guamaso. There was a great view of the cloud bank against the northern flank of Las Cañadas and it was clear where the pine and (lower) heather forest get their moisture. It was a nice hike and we passed nobody.

We then drove to Teide Observatory on Izaña. The observatory is operated by the Instituto de Astrofisica de Canarias and opened in 1964, attracting telescopes from various countries due to the good viewing conditions; it is especially well suited for observing the sun. We tried to hike the trail (trail 7) that starts between Minas de San Jose and the gondola and heads up toward Teide. The entire hike gains about 1,100 meters, we were only planning to hike the approach. Unfortunately, the small car park was full and so we headed back to a short stop at Minas de San Jose again. Montaña Blanco, which is just to the west and the source of both the lava and pyroclastics that coat the surface and provide the light color.

A flow from Mantaña Blanco contains significant obsidian. The large blocks of black volcanic glass are an interesting contrast to the buff colored glass of the pumice. The general explanation for obsidian is that it is a felsic lava that cools too quickly for crystals to grow but this is too simplistic. The obsidian adjacent to Mantaña Blanco probably had the same composition as the adjacent phonolite. A high silica content probably enabled viscous polymerization that inhibited the migration of ions but it is the low water content (less than 1%) that seems to be the critical factor. Water is important in allowing the diffusion of ions and the kinetics of mineral growth, a lack of water would limit the formation of a rock- forming minerals. Then the question becomes, why does some lava have such a low concentration of water? Another interesting note is that obsidian is usually associated with rhyolitic magma with a SiO2 content of over 70%, the phonolites of Teide-Pico contain less than 60%.

Wednesday, March 19th Today we booked a tour (Frühauf Bergwandern) that would take us up the Teleférico del Teide (gondola) and then a hike to the summit of Teide. Passes are required and can be obtained through the Teide National Park (www.reservasparquesnacionales.es) but when the summit opened for the season on Saturday, the limited passes were gone by the time we made a request. The other option is to go with a commercial tour. Christian Hernández-Mentzel ([email protected]) was our very competent guide. We headed up to the park a little after 8:00 am with a group of 5 Germans – Guten Tag!

The gondola takes you from 2,356 meters to 3,555 meters, saving you 1,199. The ride takes about 8 minutes (8 m/s). The hike to the summit (trail 10) gains 163 meters in about 0.6 kms.; it is a beautiful path up the summit cone. You know you are getting close to the summit when you smell the sulfur- dioxide from the small fumaroles (solfatara) in the crater.

There are several fumaroles that are emitting steam and the rock around the small vents tend to be bleached white. Fumaroles emit a variety of gases but water vapor (predominantly meteoric) is the dominant gas (90%). Other gases include CO2, SO2, HS, He, CO, HCl and lesser concentrations of HF,

N2, Ar, B and NH3 (ammonia). Hydrogen sulfide and hydrochloric acid (and HF) result in a very acidic environment. Gas emissions are used to monitor volcano activity; it is common for emissions to jump 5 or 10 times -6 -5 prior to an eruption. A study in 2005 found approximately 0.5 t/d CO2 and 5.7x10 to 1.6x10 t/d SO2

Teide summit crater with fumaroles. emitted, significantly lower than continuously emitting volcanoes elsewhere (2.6 – 4000 t/d). This suggests that Teide is not “reawakening” (Barrancos et al., 2005). A later study by Pérez and others (2013) found significant changes in the degassing rate that they concluded were due to subsurface magma movement.

Tenerife has a network of seismic monitors as well as geodetic monitors (GPS). Between April and June,

2004, there was an increase in seismic activity which correlated with a significant pulse of CO2 emissions from the Teide crater (up to 26.3 t/d) and SO2, HCl, CO emissions also increased. All of these gas emissions dropped off with the seismic activity after 2004. The temporal association of seismic and degassing reinforced the idea of comprehensive monitoring programs that included seismic, emissions, and geodetic.

A short trail south from the gondola station took us to an overlook of Pico Viejo. Pico Viejo held a lava lake that was approximately Pico Veijo summit crater. 800 m in diameter. As the lake level rose, lave flows were initiated and moved down its Volcanic bomb. flanks. A lava lake overflow can be seen on the left side of the photo. At some point, the lava lake drained (possibly due to a lateral vent) and the remnants of the lake can be seen as the dark magma terrace within the cone. Also along the trail there is an enormous volcanic bomb; it is approximately 2 meters in diameter and is spherical in shape. It is hard to imagine that a bomb of this size wouldn’t flatten upon impact. Although it may have rolled down the slope a ways, it is about 400 meters from the vent of Teide. Bombs up to 6 meters in diameter were ejected 600 meters from Mount Asama during a 1935 eruption. Spherical bombs are formed by surface tension that shapes the low- viscosity lava. We stopped at Roques de Garcia to, once again, look at the unusual outcrop. It is clear that several huge landslides (debris avalanches) initiated in Las Cañadas Volcano, the Roques de Garcia slide occurred over 600 ka and the Icod slide occurred around 170 ka. The semi-circular head scarp suggests that prior to the mass wasting events a caldera existed (the LCV collapse structure), the slide removed the northern part of the caldera. The Roques de Garcia probably only survived because they were adjacent to the headwall or the southern caldera margin and they were anchored by resistant dikes and volcanic necks (La Catedral). Roque Chinchado is a classic erosional remnant, supported by a thin neck that will soon collapse.

Our next stop to view some green rock exposed a few kms past Roque Chiinchado in front of Teide Volcano.

Roques de Garcia. This color is probably due to hydrothermal alteration at some time in the past. The rock is a light green color and fractures are coated with a red-brown oxidized Fe or Mn. The green color could be from epidote or chlorite, both common alteration minerals. Epidote, 3+ Ca2Al2(Fe ;Al)(SiO4)(Si2O7)O(OH), is a common secondary mineral, the product of hydrothermal alteration of feldspars, micas, pyroxenes, and amphiboles. Chlorite is a phyllosilicate, Hydrothermal alteration

(Mg,Fe)3(Si,Al)4O10, and can result from the hydrothermal alteration of pyroxene, amphibole and biotite.

It was late in the afternoon, and just the time for a beer at a road-side restaurante in the park. Our last stop was at the Lava Rosetta on the way back to Puerto de la Cruz. This is a fantastic structure that developed when radial fractures developed on a cooling cylinder or sphere of lava. The “columns” radiate from the center and increase in size toward the margin, producing a flower-like appearance. The columns that are oriented toward the top are slightly longer because they probably cooled more quickly; the columns to the side and down cooled more slowly because they were insulated by the ground. Since only a cross-section of the lava is exposed, it is difficult to tell if this is a spherical structure or part of a elongate lava flow that was moving down a pre-existing channel when is solidified. It isn’t hard to imagine that as the lava Lava Rosetta. cooled and contracted, fractures started at the cooler margins and propagated toward the center of the Rosetta as the cooling progressed and the lava solidified.

References:

Ablay, G. J., Carroll, M. R., Palmer, M. R., Marti, J., and Sparks, R. S. J., 1998, Basanite-phonolite lineages of the Teide-Pico Viejo volcanic complex, Tenerife, Canary Islands: Jour. of Petrol., v. 39, n. 5, p. 905-936.

Ablay, . ., Ernst, . . ., arti, ., and parks, . . ., 5, The 2 ka subplinian eruption of ontana Blanca, Tenerife: Bull. Of Volcanology, v. 57, p. 337-355.

Ancochea, E., Fuster, J., Ibarrola, E., Cendrero, A., Coello, J., Hernan, F., Cantagrel, J., M., and Jamond, C., 1990, Volcanic evolution of the island Tenerife (Canary Islands) in the light of new K-Ar data: Jour. Volcanol., Geotherm. Res., v. 44, p. 231-249.

Anchoch, E., Huertas, M. J., Cantagrel, J. M., Coello, J., Fuster, J. M., Arnaud, N., and Ibarrola, E., 1999, Evolution of the Canadas edifice and its implications for the origin of the Canadas Caldera (Tenerife, Canary Islands): Jour. Volcanol. Geotherm. Res., v. 88, p. 177-199.

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