The Canary Islands, Spring 2007

Professor Brad Singer led a field trip to the Canary Islands of Tenerife and La Palma from May 19 to June 1, 2007.

Students, faculty, experience “world class geology”

Text and photos by Brad Singer

After a seminar held during the 2007 spring semester on the petrologic and geophysical evolution of the Canary Islands, a group of seven graduate and two undergraduate students led by Professor Brad Singer, traveled to the islands for a two week field excursion from May 19-June 1. We were joined by former faculty member Richard Allen, now at the UC Berkeley Seismological Laboratory, who rounded out our diverse group with expertise across geophysics, igneous petrology, sedimentology, and structural geology.

The Canary Islands archipelago is a Miocene to Recent chain of volcanoes that have grown over a mantle plume beneath the eastern Atlantic Ocean. The Canaries resemble the Hawaiian Islands in many ways, but multiple stages of volcano growth are far better preserved in the Canaries owing to slower movement of the oceanic lithosphere of the African plate over the mantle plume and limited subsidence of the large volcanoes.

After the overnight flight from O’Hare to Madrid, on May 20th we boarded the plane for the island of Tenerife, the largest of the Canary Islands. Tenerife displays perhaps the most complete record of hot spot volcano evolution in the world. Geological wonders include Pico de Teide, the third highest volcano on Earth (behind Mauna Loa and Mauna Kea), and the steepest stratovolcano whose northern flank rises from sea level to the 3718 m summit in less than 13 km. Collaborator and friend, Juan Carlos Carracedo, a scientist at the Spanish government’s volcano observatory on Tenerife, was our guide for the first five days of the trip.

Dr. Juan Carlos Carracedo discusssed the complex phreatomagmatic eruptions that formed the Pico Viejo volcano

Waking to spectacular views of Pico de Teide and jet lag on the first day, we drove up from our rented “casa rurale” in the town of Orotava in the north central part of Tenerife into the Late Pleistocene Cañadas Caldera, in which the more recent Pico de Teide has grown. At 2,200 m elevation the air was cool and moist with clouds that had perched over the southwestern corner of the island. After an orientation to the caldera structure and the post-caldera lava flows, domes, and stratocones of Pico de Teide and the Pico Viejo flank vent given by Juan Carlos, we headed to the active rift zone that connects the Miocene-Pliocene shield volcano of Teno to the recent Pico de Teide cone. Here we saw evidence of mingling between basaltic rift magmas and phonolitic magmas more typical of the post-caldera stratovolcanos.

Teide National Park
Continuing the descent from the summit of Teide volcano (3718 m) to the floor of the Caldera (2000 m).

On May 22nd we headed west from Orotava along the coast, stopping to study outcrops of Late Pleistocene to Recent pyroclastic cones and lava flows comprising basalt and trachyte, to eventually traverse more than 1,500 m of thick lava flows and sheeted dike swarms of the massive Teno shield volcano that holds up the northwest corner of Tenerife. On May 23rd we headed back up into the Cañadas Caldera for a day-long 15 km walking traverse across the eastern caldera floor. Before noon we split into two groups, each ascending the 200 m tall caldera rim escarpment in locations 2 km apart, to observe lava flows and pyroclastic deposits associated with formation of the Cañadas shield volcano and its collapse to the north 200,000 years ago. The two groups compared notes and debated the lateral continuity of phonolitic ash falls and flows over a cool, but very sunny, lunch at the foot of the stunning peak of Teide.

On the 24th Juan Carlos joined us at the cable car for the ride up to near the summit of Pico de Teide, which was arguably the most spectacular day of the trip. After reaching the 3718 m summit in icy howling wind, we spend the remainder of the day on a 12 km hike down through the clouds traversing the southwest flank of the stratovolcano. We pondered the origins of phonolitic lava flows, the km-wide, 200 m deep, crater of the flank volcano Pico Viejo that last erupted in 1798, and the vast Cañadas Caldera that was laid out in color below us.

The group split up again on the 25th, some visiting the beaches near the city of Santa Cruz de Tenerife, while others explored the wild and steep exposures through the Miocene lavas of the Anaga Shield Volcano on the northeast corner of the island. This part of the trip wound up at Juan Carlos’ home for a wonderful meal with his family featuring plenty of local food and, of course, excellent wine.

JoAnne Gage
JoAnn Gage measured the orientation of basaltic dikes that cross cut Pliocene gabbroic rocks exposed by the gravitational collapse and landslide that created the Taburiente Caldera, Caldeira National Park, La Palma.

The morning of May 26th we flew to La Palma, the youngest, westernmost, and most recently active, of the Canary Islands. We arrived early to inviting weather, so decided to circumnavigate the island by way of ascending 2,400 m to the Roque de los Muchachos along the rim of the Taburiente Caldera that formed when nearly a third of the shield volcano became gravitationally unstable and collapsed catastrophically into the Atlantic Ocean 550,000 years ago. The 200 km3 of debris would have created a tsunami that is hypothesized to have struck the entire east coast of North America. After lunch in the sun at Puntagorda, on the northern flank of the Taburiente shield volcano, we examined the 300 m thick fan delta conglomerates of the El Time Formation (much to the delight of the sedimentologists), which were deposited during rapid downcutting of the volcano following the gravitational collapse. We then headed to our lodging—a hostel above a day care center, gratis thanks to Juan Carlos’ friend the mayor of Fuencaliente on the southern end of the island.

On the 27th we drove up to the northern end of the Cumbre Vieja Volcano, an N-S rift system that began to form about 120,000 years ago and which today is surmounted by dozens of historically active volcanoes. We set out hiking in thick fog along the “Ruta de Los Volcanes” and located the fault scarp along which geodedic measurements suggest the next gravitational collapse of La Palma may initiate. We were rewarded later by climbing above the clouds to the summit of the active rift just in time for lunch with breathtaking views of the Taburiente Shield Volcano and of Pico de Teide 100 km to the east on Tenerife. Next was a walk down through the intricate flow channels and levees within the pristine basaltic lavas which breached the San Martin Volcano in 1646 A.D. to flow eastward from 1346 masl into the Atlantic Ocean only ten km away.

On May 28th we drove back to the Taburiente Shield Volcano to begin an overnight hike through exposures created by the giant collapse. Lava flows and dikes of the older parts of the volcano were found to contain numerous xenoliths of gabbro, wherlite, and norite which helped students recall mineral assemblages that would come in handy the next day. Our campsite was deep inside the collapsed caldera where one gazes at the insides of the volcano—lava flows, pyroclastic deposits–dike swarms–all cropping out for thousands of meters in every direction.

The next day was another geologic highlight. The hike out of the caldera descended from the roots of the Pleistocene shield volcano into an underlying Pliocene plutonic complex—the remnants of a seamount precursor to the younger shield volcano—in which gabbros are everywhere cut by at least three generations of basaltic dikes that served as a structural geology exercise during our break for lunch. In the final kilometers we twisted our way through river sculpted outcrops of pillow lavas—wonderful! We ended this fabulous day with a long relaxing dinner on the black sand beach complete with a beautiful sunset over the Atlantic Ocean.

La Palma Cumbre Viej
Teneguia is the youngest volcano in the Canaries

Our last day on La Palma was spent along the Cumbre Vieja rift system visiting the 1949 A.D. phonolite lava flow where students managed to locate a hidden lava tube to explore. We also saw the 1585 Jedey phonolite lava flow in which students tried to identify phenocrysts of Huayanite, and finally the red-black scoria cones and basaltic lava flows of Teneguia Volcano which formed in 1971 A.D. on the island’s southernmost tip. It was difficult to begin the journey back to Madison after packing so much world-class geology and camaraderie into the first two weeks of summer.

This field trip was supported in part by Chevron and the Student Field Experiences Fund. We thank Juan Carlos Carracedo, his wife Pauline and their entire family for the most generous hospitality.

Student participants were: Ninfa Bennington, Amalia Doebbert, JoAnn Gage, Sara Greene, John Hora, Jessica Lopez, Jeremey Pesicek, Craig Schuettpelz, and Ryan Sharma.

Originally published in The Outcrop for 2007, UW-Madison Department of Geology and Geophysics, p. 11.