Discovering the World’s Largest Caldera: An Interview with Geophysicist Jenny Anne Barretto - Part 2
by Marcelle P. Villegas - April 01, 2021
“I always say that you don’t have to be a genius or a math wizard to pursue a career in STEM [Science, Technology, Engineering, Mathematics]. It may mean working harder, but your love for learning and discovery will sustain you. Never stop being curious and take every opportunity to learn.” (Jenny Anne Barretto)
Last year, Philippine Resources Journal interviewed geologist and marine geophysicist Jenny Anne Barretto during an online talk show and forum in New Zealand titled “NetKapihan”. She shared the story on how she and her team discovered the world’s largest caldera located in Benham Rise (also known as Philippine Rise) – the Apolaki Caldera.
Ms Barretto is a Filipina scientist who works in GNS Science in New Zealand. She graduated with a degree in MSc Geology from the National Institute of Geological Science in University of the Philippines (UP). She was also an instructor in UP for five years.
Since 2007, she has been assisting coastal States like the Philippines and the Sultanate Republic of Oman in delineating their continental shelves as defined in UNCLOS Article 76. Ms Barretto was a key scientist of the technical working group that successfully confirmed the continental shelf of the Philippines in the Benham Rise region.
In 2019, Ms Barretto and two colleagues, Ray Wood and John Milsom, published a paper in Marine Geology Journal titled, “Benham Rise unveiled: Morphology and structure of an Eocene large igneous province in the West Philippine Basin”. In this paper, they reported the discovery of what may be the largest caldera in the world. They named this the Apolaki Caldera, a tribute to the "god of sun and war" in Philippine mythology. How big is this caldera? It has a diameter of ~150 km, which is 90 km bigger than the Yellowstone Caldera in Wyoming, U.S.A.
“My co-authors and I were part of the Benham Rise continental shelf technical working group. Back in 2008, we only analysed the bathymetric, geological and geophysical data for the purpose of proving that Benham Rise is part of the Philippine continental shelf. That is by showing that Benham Rise is physically connected to Luzon,” Ms Barretto said.
On Part 1 of our interview, she also discussed the possible mineral resources available in the area. “With the presence of the caldera, exploration geologists will say that the possible mineral resources are volcanogenic massive sulfide (VMS) deposits which are significant sources of metals (largely Cu, Zn, Pb ± Au).”
She also noted, “The available data supports our interpretation of the existence of the caldera. However, it is not impossible that other scientists or even us (me and my co-authors) may find later evidence refuting it. It’s just how science works.”
For part 2 of this interview, we shall discuss further the features of the Apolaki Caldera, its origins and possible dangers it might pose future. We also asked Ms Barretto about the difference between working as a scientist here in the Philippines and abroad, plus her message for young people who aspire to pursue a career in science.
PRJ: Bathymetric surveys were used to identify the morphology of the caldera. What other data sets (such as seismic or gravimetric surveys) are available to model not only the surface but also the structure of the caldera?
Ms Barretto: Yes, multibeam bathymetry data was the primary data used that led to the identification of the caldera. There is only one existing multichannel seismic reflection profile that crossed the caldera from which we identified ~1km of sediment fill, which is unusual for oceanic plateaus because these submarine features are commonly blanketed by thin sediments. Single channel seismic reflection profiles across Benham Rise show less than 500 m sediment blanket which is supported by drill cores from DSDP Site 292. There was also a 2D gravity model which included a thick pocket of sediments in the same location as that depicted on the seismic profile.
I went through all the data we have from 2008 and availed of other data in the public domain. Reading John Milsom’s previous interpretations of seismic and gravity data in Benham Rise, I realized that a way to explain the relatively thick pocket of sediments on the summit that he pointed out was the presence of a caldera. So that began our work together to prove or disprove the presence of a giant caldera on Benham Rise.
The seismic interpretation and gravity model were made years before we noticed the caldera feature. The presence of the caldera gave sense to the existence of the thick pocket of sediments.
Future work should include deep penetrating 2D multichannel seismic reflection survey complemented by gravity and magnetic studies would help verify the existence of the caldera and associated structures and could also provide insight into magma chamber dimension and geometry. And of course, ultimately drilling within the caldera feature to get rock samples.
PRJ: Apolaki Caldera would be far the largest caldera in the world with 150 km diameter. Circular morphological structures of that size are known from impacts of meteors. Hence, could this not be a large impact structure?
Ms Barretto: Yes, that’s a possibility that’s why in our paper we compared Apolaki’s morphology with both impact craters and known giant calderas. Results of that comparison exercise show that Apolaki exhibit more caldera-like features than impact crater-like features.
PRJ: Such a huge caldera requires a similarly large magma-chamber or call it a huge “hot-spot”. Hot spots in the earth mantle are relatively stable but the earth crust is moving over such a hot-spot and creates a chain of volcanoes (see Hawaii island chain). In the case of Apolaki, the crust was not moving over the hot spot and volcanic activities occurred at stable positions. Could that not be an indication that the volcanic activity was much smaller without forming a caldera? Hence, the structure might be caused by an impact?
Ms Barretto: Yes, huge calderas imply an underlying equally sized magma chamber. In our paper, we suggested that the formation of the Apolaki Caldera (the collapse) may not have been simply caused by magma withdrawal from its magma chamber. Pre-existing large scale structures (i.e. faults and rifts) related to seafloor spreading and rifting most likely facilitated the collapse.
The lithosphere on which Benham Rise (and of course, Apolaki Caldera) was moving over a hot spot. The mantle plume or hot spot supplying the magma chamber that formed Apolaki Caldera is believed (by scientists who have worked in the region) to coincide with a spreading ridge (the now extinct Central Basin Spreading Center). So as spreading was occurring, the lithospheric plates on either side of the spreading ridge were moving away from the ridge. At the same time, the mantle plume underneath was supplying magma in excess of what the spreading ridge would normally produce and therefore create a chain of oceanic plateaus. Each oceanic plateau is split as the lithospheric plates moved away from the spreading ridge creating paired plateaus on either side, like twins. Urdaneta Plateau is interpreted by many ay Benham Rise’s twin. They are equidistant from the Central Basin Spreading Center and have similar ages. Oki-Daito Rise is an older oceanic plateau on the Urdaneta Plateau’s side. It was hypothesized by Ishizuka et al. (2013) that its twin which is supposed to be on Benham Rise’s side has either subducted or accreted with the Philippines.
PRJ: Do you think the presence of the Apolaki Caldera will put the Filipino fishermen in danger in the future?
Ms Barretto: No. Available data show that volcanism ended on Benham Rise (including its spurs) about 26 million years ago. Threat of a volcanic eruption in that area is very low.
PRJ: What are your future projects or current endeavours with regards to marine geophysics and geology?
Ms Barretto: For New Zealand, I’m currently involved in a research programme looking at next generation geothermal resources. I help put together available magnetic data for the Taupo Volcanic Zone which will help find deeper geothermal energy sources.
I’m also leading a science education outreach project funded by the NZ government. My team and I will bring an augmented reality sandbox in different remote North Island primary schools teaching students about land and water interaction.
For the Philippines, I’m currently doing research with John Milsom and Ronaldo Gatchalian of NAMRIA about the gravity variations over the Zambales Ophiolite. There’s also ongoing work to explain the Luzon syntaxis (the bent shape of Luzon).
There’s more work to be done on Benham Rise, but at the moment we are unable to find funds to do them.
PRJ: What are some of the challenges or difficulties you have experienced as a geologist/marine geophysicist in the Philippines? How does it compare pursuing this career in New Zealand?
Ms Barretto: Funding for research is always a challenge for scientists anywhere in the world, but more so in developing countries like the Philippines. Like anywhere, we scientists in NZ need to write proposals and compete for government funding. However, there is more funding for research available here in NZ than in the Philippines. There is more support for scientists.
Working in NZ is also more relaxed with no need to beat the traffic to and from work. Even if government pay in NZ is less compared to industry, it is still enough to have a decent living. Back in PH, I have to do consultancy work in addition to my teaching job at UP to make ends meet.
PRJ: For the young people, what message would you like to impart to them that would encourage them to pursue a career in geology or in any field in science?
Ms Barretto: I always say that you don’t have to be a genius or a math wizard to pursue a career in STEM [Science, Technology, Engineering, Mathematics]. It may mean working harder, but your love for learning and discovery will sustain you. Never stop being curious and take every opportunity to learn.
Thank you, Ms Jenny Anne Barretto for sharing your amazing story, and GNS Science for the opportunity to write about this discovery and study. Thank you, Sir Rene Molina and NetKapihan for inviting me as panelist in your radio show in New Zealand. PRJ would also like to thank Dr Friedrich Bandelow for his contribution in the technical discussion in the interview, and science journalist Angelica Yang for guidance and support.
Philippine Resources - September 24, 2021
DOTr, Pasay City sign deal for monorail, flyover extension
Residents and those working in Pasay City will soon enjoy easier public transportation after the Department of Transportation (DOTr) and the city government signed a deal for the construction of a monorail and extension of the Epifanio Delos Santos Avenue (Edsa)-Tramo flyover. In a live broadcast on Facebook on Wednesday, DOTr Secretary Arthur Tugade and Pasay City Mayor Emi Calixto-Rubiano signed the memorandum of agreement (MOA) for the proposed Integrated Pasay Monorail and Edsa-Tramo flyover extension project. Tugade said the project will be interoperable with the Light Rail Transit Line 1 (LRT-1), Metro Rail Transit Line 3 (MRT-3), the Edsa Busway, and the Edsa Greenways. “[Ito ay] makapagbibigay ng mas mabilis at episyenteng biyahe sa mga pasahero. Magiging mas madali na rin ang access patungong central business district (CBD) ng Pasay (This will provide fast and efficient travel to passengers. Access to Pasay CBD will also be easier),” Tugade said. Aside from its benefits to commuters, he said the project will also create jobs. “Ang paulit-ulit kong sinasabi na karugtong ng mga proyekto para sa kaunlaran ay trabaho para sa Pilipino (What I have always been saying is that development projects go hand-in-hand with jobs for Filipinos),” Tugade said. He said the project is a partnership between the DOTr, Pasay City government, and SM Prime Holdings. “Makakaasa 'ho kayong magpapatuloy ang DOTr sa pagsusulong ng mga proyekto para sa ikauunlad ng pampublikong transportasyon sa bansa (You can be rest assured that the DOTr will continue to promote projects for the development of public transportation in the country),” Tugade said. The MOA signing was witnessed by Pasay City Vice Mayor Noel del Rosario, DOTr Undersecretary for Finance Giovanni Lopez, Undersecretary for Legal Affairs Reinier Paul Yebra, Undersecretary for Railways Timothy John Batan, SM Prime Holdings President Jeffrey Lim, and other representatives from the Pasay City government and the private sector. On Sept. 7, the Pasay City government and the SM Prime Holdings made a joint presentation on the project to the DOTr. By Raymond Carl Dela Cruz Article courtesy of the Philippine News Agency
Philippine Resources - September 24, 2021
DOTr eyes GenSan airport as alternate int'l gateway
Photo credit: Department of Transportation The Department of Transportation (DOTr) is pushing for the inclusion of the newly rehabilitated and expanded airport here as among the alternate gateways for returning Overseas Filipino Workers (OFWs) and international travelers. DOTr Secretary Arthur Tugade proposed the move on Thursday as he personally led the formal unveiling and inauguration of the city airport’s new passenger terminal building and other completed facilities. He said the city’s international standard airport can accommodate airline passengers coming in from as far as the Middle East. Tugade said it can be realized once the proposed increase in the daily cap for returning OFWs, currently at 2,000 for the Ninoy Aquino International Airport (NAIA), is approved. Once the cap is expanded, he said NAIA might “choke” with the influx of airline passengers from various countries. “If we will increase the cap, we need to expand our gateways and not limit them to Clark, Cebu, and NAIA. We can include GenSan among the gateways for travelers from Doha who are going to Manila,” he said in a press conference. He said they will propose such strategy with the airlines serving the international routes, including the Philippine Airlines, and seek the approval of the city government. The other possible alternate gateways could be the Laoag International Airport in Ilocos Norte and the Bohol-Panglao International Airport, Tugade said. The rehabilitated and expanded General Santos Airport passenger terminal building, which was completed early this month, is part of the PHP959-million upgrade implemented by the national government. The other completed components are the procurement and installation of navigational aids and the construction of the new Civil Aviation Authority of the Philippines (CAAP) administration building at the airport. Under the project, Tugade said the passenger terminal area has tripled in size from 4,000 to 12,000 square meters. “This will allow the airport to accommodate more passengers and provide them comfortable and convenient travel,” he said in his speech. A DOTr report said the larger passenger terminal building can now accommodate around 2 million passengers annually, a significant jump from the previous 800,000 per year. Tugade said the improvement at the city airport will continue next year with the upgrading of its air control tower, which he considered as “too low.” He said they will build a “higher and modernized” tower in 2022 to make it “more world-class” and can easily adjust to the needs of the airport. The official said the upgrading of the airport, which started in 2018, is among the agency and the national government’s top priorities in Mindanao. He said the initiative is part of the government’s efforts to bring more progress and economic opportunities in Mindanao, which “suffered from long years of neglect in terms of development.” Tugade said they endeavored to implement these projects despite the challenges posed by the continuing coronavirus disease 2019 (Covid-19) pandemic to pursue their goal of giving a “comfortable and convenient life” to Filipinos. “After the pandemic, we want all these developments in place and ready to benefit the people,” he said. In a video message, President Rodrigo Duterte commended the DOTr, the local government, and concerned stakeholders for completing the projects at the city airport amid the Covid-19 pandemic. He said the city has “gone a long way” in terms of the development of its air connectivity and airport facilities. “The rehabilitation and expansion of the airport passenger terminal building, among others, will truly boost General Santos City’s role as an agro-industrial and eco-tourism hub,” the President said. City Mayor Ronnel Rivera lauded the national government for helping the city realize its dream of having an international-standard airport. Aside from the expanded passenger terminal building, the airport is now capable of accommodating bigger aircraft like Boeing 737 and 747, as well as Airbus A330, A340, and A350. “(What) we are seeing now is a result of multisectoral commitment and dedication in various stages of the airport development, which includes coordination of several initiatives, preparation of the airport master plan, operations, and marketing,” he said. The mayor said the local government will continue to engage with prospective investors and airlines for the opening of more flights to and from the airport and the development of adjacent areas. He cited the proposed establishment of an aerotropolis or growth area centered on the city airport and its surrounding areas. “We are opening a wide array of opportunities, not only on the improvement of our infrastructure facilities but also in terms of investments that will generate more economic opportunities for the city and the entire region (Soccsksargen),” he said. Aside from the inauguration of the airport projects, Tugade also led the unveiling of completed initiatives at the Makar port here. The DOTr said it includes the construction of the Port Operations Building and other vital facilities, which includes a parking area, covered court, port manager’s quarter or Day Care Center, and drainage system. “The improved port of Makar will now offer safer, comfortable, and a more convenient port experience to passengers, while ensuring a faster turnaround for vessels, cargo trucks, and other ancillary service providers,” it said. Article courtesy of the Philippine News Agency
Philippine Resources - September 22, 2021
Cebu-Cordova Link Expressway 83% Complete
Photo credit: Cebu-Cordova Link Expressway As of August 31, 2021, the construction progress of the Cebu-Cordova Link Expressway (CCLEX) project was at 83.84 percent. The P30-billion toll bridge, which will be substantially completed by the end of 2021, will use a full electronic toll system when it opens to motorists in the first quarter of 2022 to enable faster traffic flow and seamless travel. The project recently marked a milestone with the completion of the installation of all 56 stay cables that hold the main bridge deck. On September 11, the Cebu Cordova Link Expressway Corporation (CCLEC), through its contractor, installed the last and longest stay cable, which is 219 meters long. The gap on the main bridge, on the other hand, is now down to only two meters before span closure and preparations are underway for the lowering of the form travelers. These form travelers, which weigh 500 tons in each tower, were used to construct the main bridge’s pier table and deck. Also, all 434 NU (Nebraska University) girders for the entire project have already been installed. With this, the mobile launching gantry used to install the girders have been demobilized. At the Cebu South Coastal Road (CSCR) on ramp and off ramp sections of CCLEX, construction of its substructures is complete. Ongoing works are now on the installation of precast planks and the concreting of deck slab. Also finished is the 200-meter pedestrian footbridge beside the CSCR with all six prefabricated steel walkways already installed. The footbridge will start near the U-turn slot of the South Road Properties’ welcome tower and will connect to the on-ramp sidewalk of CCLEX. At the Cebu viaduct, the construction of deck slab is ongoing. The Cordova viaduct, on the other hand, is now structurally complete with its substructure already done. Installation of handrails are underway. At the causeway, embankment works continue to progress with the placing of 20 vent pipes, which equalize the flow of seawater along the Cordova Channel, is finished. Also structurally complete are the four low-level bridges along the causeway, which will provide fishermen continued access to their fishing grounds. Aside from these, works are ongoing for the toll plaza and the CCLEX Operations and Maintenance Center. CCLEX, highlighted by its iconic crosses on top of the twin pylons of the cable-stayed main bridge over the Mactan Channel, is Metro Pacific Tollways Corporation’s (MPTC) first toll road project outside Luzon. CCLEX, which will be the third link to Mactan Island from Cordova Municipality to mainland Cebu through Cebu City’s South Road Properties, has a design speed of 80 kilometers per hour (kph) and a navigational clearance or height of 51 meters to allow large vessels to pass underneath the bridge. Not only is CCLEX seen to reduce traffic and make traveling more convenient but also spur trade activities and open greater economic opportunities for Cebu and the rest of the Visayas region. CCLEX is a project of Cebu Cordova Link Expressway Corporation (CCLEC), in partnership with the local government units of Cebu City and Municipality of Cordova. CCLEC is a wholly owned subsidiary of MPTC, the toll road arm of Metro Pacific Investments Corporation (MPIC), a publicly listed infrastructure holding company and a member of the MVP Group of Companies. MPTC is the largest toll road concessionaire and operator in the Philippines, which expansion goals include establishing toll operations in the Visayas, other parts of the Philippines, and in neighboring countries notably Vietnam, and Indonesia. Article courtesy of Cebu-Cordova Link Expressway