Canary Islands, Spain

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

Hierro, extending the track.

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

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

Island age trend and overlap of the island aprons (Guillou et al., 2004)

Age vs distance for Canary and Hawaiian Islands (Carracedo

et al., 1998)

Islands and seamounts of the Canary Islands

(Carracedo and Perez-Torrado, 2013)

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).

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. Teide 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

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. 40

Ar/39

Ar

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).

Las Cañadas Caldera (Carracedo and Perez-Torrado, 2013)

Location and ages of landslides (Mason et al., 2007)

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

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).

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

Recent volcanism on Tenerife (Carracedo et al, 2007)

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.

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.

Ground water galleries (Carracedo, 19994)

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.

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

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

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

Roque de Agando, a volcanic plug

Map of the Cueva de Viento lava tube system. Colors represent different levels.

extinct animals such as a giant rat (Canariomys bravoi) and giant lizard (Lacerta goliath). Mummified

remains of the Guanches, 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

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

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

Terraces in the lava tube

Lava drips on the roof of a lava 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

Las Canadas Caldera (LCC), Teide (T),

Pico Viejo (PV), Montana Blanca (MB)

from Ablay and others (1998).

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,

feldspathoids (nepheline and leucite). The feldspathoids

Composition of Peide and pico Viejo

phonolites 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.

From Roques de Garcia we drove west and turned onto

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

part of the park. (5 km2) We left the park on TF-38,

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.

Las Narices del Teide on Pico Viejo.

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 (chmtzel@gmail.com) 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

prior to an eruption. A study in 2005 found approximately 0.5 t/d CO2 and 5.7x10-6

to 1.6x10-5

t/d SO2

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

800 m in diameter.

As the lake level rose, lave flows were initiated and moved down its

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.

Teide summit crater with fumaroles.

Volcanic bomb.

Pico Veijo summit crater.

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

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,

Ca2Al2(Fe3+

;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,

(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

Roque Chiinchado in front of Teide Volcano.

Hydrothermal alteration

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.

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