Guest Blog by
Dr. Jaime A. Cavazos-Álvarez
Volcanologist and Postdoctoral Researcher
Instituto de Geociencias, Universidad Nacional Autónoma de México (UNAM)
jcavazos@geociencias.unam.mx
When gazing at a peaceful lake, have you ever wondered about its origin? What natural treasures are hidden underwater? How are rocks and life continuously adapting? Well, usually the answers to these questions are far from their characteristic steady landscapes. The answers to these questions lie underwater, usually leaving much to our imagination. Now, with BioBase we are closer than ever in seeing what’s inside these lakes. And, as expected, while solving these questions many others emerged. I will take this opportunity to share a couple of case studies of fascinating lakes in Mexico, and how BioBase has opened new paths towards their understanding.
Volcanic lakes for understanding Earth and life
While some lakes form through slow and gentle geological processes, others emerge from some of Earth’s most violent and explosive events: volcanic eruptions. Among these, maar volcanoes stand out as particularly enigmatic, often concealing their eruptive history beneath a lake-filled crater.
Moreover, they are like time capsules. Using advanced BioBase sonar mapping, we can observe the hidden depths of these lakes and understand their history. But that’s just the beginning! Extreme environments teem with unique life, and we’re using cutting-edge DNA techniques to explore the microscopic organisms thriving in these volcanic craters, piecing together their story alongside the geological one.
The challenge in studying maar lakes
The origin of maar volcanoes is among the most complex geological processes on Earth, as these are created by powerful underground explosions when magma interacts with groundwater. The resulting craters typically span kilometers in diameter and reach depths of hundreds of meters. Interpreting their history relies heavily on analyzing their morphology, especially their crater rim and floor shapes.
Over the years, chasing all types of volcanoes to tell me their stories, I have found that they all have unique and often complex shapes. Maar volcanoes are not the exception. This is because, unlike the classic circular craters seen in geology textbooks, most of them have irregular shapes resulting from the overlapping of multiple explosions occurring at different locations within the same eruption. This makes their geological interpretation particularly challenging.
Complexity increases when these craters are filled with water, which is also a very common scenario. By not seeing the underwater morphology, we lose sight of the scars made during the eruptive explosions, making it exceptionally challenging for us as volcanologists who aim to reconstruct their formation and evolution.
To overcome this challenging task, we deployed a novel study of two maar lakes in the Serdán-Oriental Basin volcanic field (Mexico) using BioBase bathymetry surveying technology. After sailing and mapping, we created detailed Digital Depth Models for each lake, revealing their hidden morphologies and gaining unprecedented insight into their explosive past and peaceful present.
Complex Shapes of Maar Craters
The La Preciosa and Quechulac maars, two adjacent and complex-shaped volcanoes, are the study subjects that show how BioBase effectively solves the challenges in studying maar lakes (Figure 1). Their pristine morphologies, preserved by the arid conditions of central Mexico, have unique features and stories that need to be revealed.
La Preciosa maar exhibits a particularly intriguing anomaly: half of its typical tephra ring (a rim formed by ejected volcanic material) is missing (Figure 2). This deviation from the usual maar structure raises questions about its formation and post-eruptive modifications: Was it not originally formed, and why? And if it was formed, why isn’t it there anymore? Is it underwater?
Meanwhile, Quechulac maar contains an irregularly shaped island near its center, an unusual feature for a maar volcano that typically undergoes explosive excavation (Figure 3). How did this island form, and what does it reveal about the lake’s geological history? In both cases, little can be said without understanding their underwater morphologies.
The power of BioBase for High-Resolution underwater mapping
Bathymetric mapping using Lowrance Hook 7 consumer sonar over an inflatable kayak (Video below) and BioBase allowed us to visualize the full subaquatic structure of these craters, providing unprecedented detail on their geomorphology.
When I first met these breathtaking lakes, I had no idea about their depth, much less what the morphology was like down there. While sailing on my kayak and looking at the sonar monitor (Figure 4), hypotheses erupted! Bold ideas about the origin and evolution of these volcanoes fueled our discussions. After that, the resulting bathymetric maps showed us how these two unusual maar lakes look underwater.
La Preciosa seems to have a contrasting morphology when comparing its northern and southern parts (Video 2 below). In the former, the depth is significantly higher and steeper. Meanwhile, it seems to have a gentler and shallower floor in the south. Regarding the crater rim in the south, no evidence of its presence is underwater.
In Quechulac, the bathymetric map reveals a very irregular crater floor (Video 3 below). Among several features, its highlight is a hidden subaquatic range that practically crosses the crater north to south and which hosts the island. In both cases, and beyond the corresponding geological interpretations, these morphologies wouldn’t be seen without BioBase surveying.
At the time of this post, we are also employing high-resolution drone surveying techniques to characterize the outer side of these volcanoes. We aim to construct a comprehensive Digital Elevation Model that integrates their terrestrial and underwater morphologies (Cavazos-Alvarez et al., in prep). Our findings are expected to provide reliable evidence of how these fascinating geological landforms formed, and this methodology as a game-changer for studying volcanic lakes worldwide with the high resolution that BioBase provides.
Why does this matter?
Studies such as these have multiple aims beyond knowing how volcanoes work. First, it is important to know that these maars form part of an active volcanic field with hundreds of other volcanoes that have erupted in Quaternary times, located near highly populated areas in central México. So, describing how and when these volcanoes may erupt is imperative to prevent natural disasters.
Also, as said before, maar lakes serve as time capsules, particularly of environmental changes. The studied maars are characterized by their biological and sedimentological activity that forms incredible microbialite communities (Figure 5). The sediments and microbialites within these lakes record past climatic conditions, biological activity, and even human influences over thousands of years. Understanding their morphology and eruptive history is key to accurately interpreting these valuable geological records. We are about to know more about this with the help of the bottom hardness information using this powerful BioBase tool (Figure 6).
Another important application is understanding the relationship between craters morphologies, the present ecosystems, and biological preservation. Maar lakes are closed environments prone to the formation of endemic fauna and flora species. The best examples of this are our study cases. Our preliminary data indicates that La Preciosa and Quechulac maar have distinct ecosystems despite being only 2 km apart. To support these findings, BioBase sonar logs represent a powerful tool, as they may tell us a lot of information about the distribution of the subaquatic plants (Figure 7) and the size and location of the fish species (Figures 8 and 9). This accompanies an accurate quantification of the freshwater reservoirs, treasures in semi-desertic and hydric-stressed areas such as central Mexico.
This becomes even more interesting when looking at the microscopic universe. Remember that these craters form from extremely violent explosions that, in a certain way, “reset”, the ecosystem, with a newly formed environment made of nutrient-rich volcanic ash. This makes these unique ecosystems home to diverse microbial communities that have adapted to harsh conditions, including high temperatures, extreme pH levels, and elevated concentrations of metals and minerals. The bathymetric maps, coupled with DNA, geochemical, and petrophysical studies on these microbiomes (Figure 10), will tell us much more about microbial adaptation, evolution, and potential biotechnological applications (Moguel et al. in progress).
By analyzing the DNA left behind by these tiny organisms, we can learn about the changes they’ve undergone over time and how they interact with their environment. Extreme environments exist all over our planet, from icy polar regions and deep-sea hydrothermal vents to scorching hot springs and acidic lakes. Volcanic lakes, with their own unique blend of extreme conditions, offer a fascinating opportunity to understand how geological forces shape the evolution and interactions of microbial life.
Finally, let’s think out of the box. The methodology used in this study, strongly supported by BioBase, can be applied to other volcanic lakes and even different geological settings. This opens new possibilities for studying submerged landforms and understanding Earth’s dynamic geological past in greater detail than ever before.
A New Perspective on Maar Volcanoes
Many maar volcanoes host inner lakes, each recording unique and interesting geologic histories to tell. By looking beneath the surface at this resolution, we can unravel the hidden stories locked within any maar volcano lake, in our case for La Preciosa and Quechulac. These preliminary findings demonstrate how modern technology can shed light on the intricate history of explosive eruptions and their aftermath. As digital mapping techniques advance, we can expect even deeper insights into Earth’s volcanic landscapes, helping us better understand our planet’s past and future geological activity. These are the first two volcanic stories of many we must share.
Credits to the team:
Gerardo Carrasco-Núñez – Volcanologist and Senior Researcher at Instituto de Geociencias, UNAM
Bárbara Moguel – Biologist and Academic at Universidad de las Américas Puebla
Javier Mancera-Alejándrez – Engineer and Academic at Facultad de Ingeniería Geológica, UNAM
Sergio Macías-Medrano – Engineer and Academic at Facultad de Ingeniería Geológica, UNAM
Special thanks to Ray Valley at BioBase for editing support
