Our ocean is an incredibly vast and mysterious place. And there is no place where that is more evident than the deepest ocean area in the world: the legendary Mariana Trench. Located east of the Philippines, the Mariana Trench lies in the Mariana Archipelago in the western portion of the North Pacific. The greater area of the Mariana Trench Marine National Monument is made up of more than 95,000 square miles of ocean. Beneath these waters lie incredibly complex aggregations of submerged islands and volcanoes … and of course, an astoundingly massive trench.

Dive in with us to have your biggest questions answered about the famed Mariana Trench.

How deep is the Mariana Trench?

The deepest part of the Mariana Trench, known as Challenger Deep, is almost 36,000 feet below the ocean’s surface. For context, Mount Everest is about 29,000 feet above sea level, so the Mariana Trench is about 7,000 feet deeper than Mount Everest is tall. For one more comparison, the RMS Titanic lies at a depth of about 12,500 feet below sea level. The Challenger Deep is in waters nearly three times deeper than this ship’s final resting place.

Due to its enormous size, the Mariana Trench has at times been affectionately nicknamed the Grand Canyon of the ocean. This is certainly a picturesque image, but don’t let the mammoth size of this U.S. national terrestrial park fool you into thinking the Mariana Trench matches its size. The trench’s footprint is estimated to be 120 times larger than the Grand Canyon’s, and to reach the bottom of Challenger Deep, you’d need to descend through almost six Grand Canyons stacked on top of each other before you’d reach the seafloor.

Oh … and did we mention it’s five times wider than it is deep? It’s about 43 miles wide!

What is Challenger Deep, and how long would it take to reach it?

Challenger Deep is the deepest point of the Mariana Trench. Fewer than 30 people have ever journeyed to this area. The trek below the surface is long, dark and time-consuming, and it’s not an expedition considered lightly by scientists and explorers.

The first people to descend into the depths of this area in 1960 were oceanographers Jacques Piccard and Don Walsh, and it took them close to five hours to reach Challenger Deep. Since then, more advanced submersibles have been created, but it still takes two to four hours for modern vessels to reach such depths. For example, explorer and filmmaker James Cameron reached the seafloor in a little more than 2.5 hours in the first documented solo submarine dive to the area, and it took oceanographer Dr. Dawn Wright about four hours in 2022. It is crucial that these submersibles descend slowly and steadily beneath the surface, as the immense water pressure compounds with every mile a submersible descends. Speaking of pressure …

What is the water pressure at the bottom of the Mariana Trench?

If you thought the depth of the Mariana Trench was its only jaw-dropping feature, think again. Water pressure is one of the most important factors affecting deep-sea life. In the ocean, pressure increases by one atmosphere for every 33 feet (10 meters) of depth. One atmosphere (a unit of measurement for pressure equivalent to average air pressure at sea level) is equal to about 14.7 pounds per square inch (PSI), which is the approximate standard atmospheric pressure at sea level. If you were to convert atmospheric pressure into weight, one atmosphere is about the weight of a bowling ball. Stay with me, friends.

If a vessel were to dive 2,000 feet below the surface, the pressure would equal that of 60 bowling balls stacked atop every square inch of that submersible. But 60 bowling balls is simply nothing compared to the pressure in the Mariana Trench. The atmospheric pressure at the depths of Challenger Deep is equal to about 16,000 PSI. That pressure is about the same as the weight of an entire full-grown elephant on every square inch of a submersible!

Need a more extreme comparison? If a human were to be placed at the bottom of the Mariana Trench, the pressure would be equal to that of 50 jumbo jets piled on top of a person!

Do any animals live in the Mariana Trench?

The depths of the Mariana Trench come with immense pressure and extreme darkness, but somehow, life finds a way to survive. Organisms that live at an extreme depth, like that of Challenger Deep, have to be highly adapted to low temperatures (typically just above freezing), high pressure and virtually no light at all.

Species found in the depths of the Mariana Trench might look vastly different from animals from other ocean depths because their anatomy has been refined to thrive in harsh conditions. At such great depths, these animals typically depend on chemosynthesis (using nutrient-rich waters being pumped out of hydrothermal vents) or descending detritus (dead matter that has fallen from higher parts of the ocean) for food, such as whale falls. Just a handful of these animals include species of octopuses and squids, sea cucumbers, amphipods, sea jellies, shrimp, sea worms and some wild-looking fish!

In 2025, more than 7,000 new species were discovered in the Mariana Trench, including the hadal snailfish (Pseudoliparis swirei). This is the deepest-dwelling fish currently known to science. Now, the fish has been dubbed “the Mariana snailfish.”

How was the Mariana Trench formed?

The process by which the Mariana Trench was created is a geologically fascinating one known as subduction. On the Earth’s surface, there are thin plates that cover the planet’s mantle, which is made of molten rock. If two of these plates collide, one pushes down into the Earth’s mantle while the other is pushed over the bottom plate. When this happens, a trench is formed from the drag of the bottom plate. This process can sometimes create incredibly strong earthquakes. The plates that forged the Mariana Trench’s creation are estimated to be up to approximately 180 million years old.

This trench was unknown to scientists until 1875. It was then that a team of explorers on the HMS Challenger measured the depth of the sea by simply lowering a weighted rope into the water. They were baffled when they measured that first portion of the seafloor to be five miles below the surface. And so was born the origin of some of the most daring deep-sea explorations known to mankind to date.

Is the Mariana Trench protected?

The Mariana Trench is in waters off Guam and the Mariana Islands. The region is protected from some human activities under its status as a marine monument. The creation of the Mariana Trench Marine National Monument signified that international, national and local leaders all recognize the importance of protecting this area.

However, just because the region is protected does not mean it’s not vulnerable to modern threats to ocean health. Plastic bags have been spotted in the Mariana Trench during several expeditions, highlighting the far-reaching impact of the marine debris problem. No corner of our ocean is safe from the ever-present threat of plastic pollution. The reality of a changing climate makes the future well-being of wondrous places like the Mariana Trench uncertain. What’s more: More than 70% of the global ocean has yet to be mapped. And what we don’t yet know about, we cannot wisely work to protect.

It’s up to us to work together to defend our ocean, from the sandy shores of our favorite beaches to the deepest, darkest parts of the sea. Together, we can work to protect our ocean as a whole, which ultimately helps protect treasured places like Challenger Deep.

Find out how you can join Ocean Conservancy’s wave of momentum to secure a healthy ocean and a thriving planet, forever and for everyone!

The post The Mysteries of the Mariana Trench appeared first on Ocean Conservancy.

The Mysteries of the Mariana Trench

Intro

At the western tip of Luzon, which is the biggest island of the Philippines, lies the small coastal town of Bolinao. Tourists seldom find their way here as it takes around seven hours to get here by bus from Manila. Still, you can spot foreigners walking around every now and then, but they really stand out among the Filipinos. A reason for their presence is often that they study or work at the Bolinao Marine Laboratory (BML), which belongs to the University of the Philippines (UP). It is one of the seven research institutions participating in the GAME project 2026. Every year, GAME brings together Master’s students from all over the world to experience different cultures and conduct globally replicated experiments in marine ecology.

This year’s Team Philippines consists of Jona, a Filipino master student of Marine Biology at the University of the Philippines, and Konstantin, a German student who is enrolled in the Master programme „Ecology and Evolution“ at Freiburg University. As part of GAME 2026, we are currently staying at BML for 6 months to run experiments about the influence of underwater soundscapes on the colonization of marine hardbottoms.

Where are we?

At the BML, we live in a dormitory together with many other students and scientists mostly from the Philippines and a few international interns. At almost any time of the day there is someone in the kitchen to hang out with, eat together, or simply have a chat. It is easy to make friends in this little community. The way to work is just a short walk along a forest path, where we can pick mangos for a snack and spot butterflies, birds, or even wild macaques climbing through the trees. After crossing a street, we reach the institute. But instead of enjoying the cool temperatures of the laboratories, we spend most of our working days outside, doing fieldwork in or near the water.

On Fridays, Konstantin experiences real Filipino culture during an almost weekly party at the institute with karaoke and lots of food and drinks. And Jona even brought some German culture to the Philippines by baking German bread for everyone.

What do we do?

Even though Bolinao is a remote place, it can get quite loud. Tricycles and jeepneys pass by, children play basketball in the streets, and karaoke can be heard almost everywhere and at any time. But just a few meters offshore, the soundscape changes. Beneath the surface of the ocean, you enter a world filled with sounds that are not so familiar to humans. When you dive down, alongside the rhythm of your own breathing, you might hear the crackling snaps of shrimp, the grunts of fish, or the rumble of waves rolling overhead. Together, these sounds form a natural underwater symphony which, however, can easily be interrupted by the noise of passing boats.

Marine organisms use sounds to communicate and to gather information about their environment, and there is growing evidence that this also applies to the larvae of sessile invertebrates such as mussels, barnacles and tunicates. During their pelagic life they are presumably able to use sounds for finding their way to suitable habitats, in which the sessile adult life stage can survive and reproduce. But what happens when these natural soundscapes are disturbed by anthropogenic noise? And what is the effect when the soundscape in a degraded reef gets enriched with sounds of a healthy coral reef?

In our experiments, which we just finished a few days ago, we investigated how different underwater soundscapes influence the colonization of hard substrata by the larvae of marine invertebrates. For this, we placed PVC settlement panels in the water and exposed them to playbacks of either boat noise, or amplified recordings from healthy coral reefs. A further group of panels was not exposed to any playbacks. By comparing the communities that establish under these different acoustic conditions, we can determine whether soundscapes affect the settlement of larvae.

Challenges

In contrast to the other GAME teams of this year’s project, we don’t have a jetty at BML. So, our first challenge was to build a setup that could carry an MP3 player for the soundscape playbacks, an amplifier, and an underwater speaker, which all need electricity supply, and position it about 30 to 50 meters away from the beach.

We ended up building a floating frame that carries the settlement panels as well as the underwater speaker, and combined it with a waterproof box, which was above the waterline and contained all the sensitive technical equipment. The box was firmly sealed so that it withstood waves and heavy monsoon rains, while its interior remained dry. At the same time, it was protected with a reflective car cover to prevent the technical equipment from overheating, as the box was constantly exposed to the burning tropical sun. To supply the set up with electricity, we – with the help of technicians and divers – rammed long bamboo poles into the seafloor and attached a cable to them that was connected to an electrical outlet on land.

As a consequence of this particular set up, every time we want accessed it, we either went snorkeling or took a boat. Hence, we had to plan our work according to the tides. We also needed to avoid the hottest hours of the day, and sometimes we needed to hurry because a storm was approaching. In the end, you could say that we learned to live in the rhythm of Mother Nature.

After some test runs, everything was ready and we could finally start the experiments. From that moment on, we regularly inspected the frames to check whether everything was still in place and whether there were any damages or malfunctions. So, we still had to go into the water almost every day. It was beautiful to make a small detour while working to see some nudibranchs, octopus or pufferfish and get to know the local underwater environment better every day. Once a month we took all the settlement panels out of the water to collect data about the abundance of single species and to document the community composition. Already after a few weeks in the water, many barnacles had settled on the panels. At a later stage, they dominated the artificial substrates together with macroalgae and black mussels. Furthermore, we could detect different species of ascidians, polychaetas, and hydrozoans, which, however, only occurred in very low abundances.

Alongside with the preparations of the experimental set up, every few weeks, Konstantin was able to join the coral research group during their fieldwork and went diving with them. This how we got our recordings of sounds from nearby healthy coral reefs. He deployed underwater microphones (hydrophones) while diving and since this task took only some minutes of the dive, he often still had enough air and time to enjoy the underwater world of the Philippines more closely.

Life in Bolinao

To put it in a nutshell, life here is a mix of relaxing beach vibes, lively markets in the city center and a wonderful community in and around the institute. A foundational value embedded in Filipino communities is Bayanihan, which embodies unity, cooperation, and collective volunteerism, where individuals work together toward a common goal without expecting personal gain or reward. This is something we feel and experience at the institute, as any individual is willing to provide help without asking for anything in return.

Science has a very strong application-oriented status here. Within the working groups at the institute, people often discuss the benefit of their research to the community. We also talked to local fishermen. They were very curious about our work and told us how they could already make use of previous research by the institute and increase their income at mussel farms.

Our experiment also could help these fishermen in the future. If we gain a better understanding of how soundscapes affect marine life, we could use that knowledge to prevent the decline of biodiversity in these waters. This would enable the community to secure stable access to the natural marine resources that serve as an important source of food and income here.

The end of our experiments

The Philippines experience 20 typhoons in a year on average and most of them hit the country during the northwest monsoon between July through October, which is overlapping with the last phase of our experiments. The frames we deployed were built to go along with the waves, but strong waves with heavy rains inflicted some damage on them. Because of that and since further storms were about to come, we decided to terminate the experiments some weeks earlier than planned.

We didn’t do much analysis of the data that we collected yet, but the first results are already fascinating. When comparing the communities that established under the influence of boat noise with those that developed in the absence of playbacks, it seems that the noise decreased the communities‘ biomass and biodiversity while it also altered their composition.

For assessing the dry weight of the organisms that colonized the panels, we scraped off everything that grew on their surfaces and dried this material in an electric dryer. After this work, the whole laboratory building smelled like a fish market. On the next day, we could already see that people took notice as many fans appeared on the hallway to blow away that smell. Luckily, everyone has been very kind and patient, helping us with ventilation and cleaning and simply putting up with the smell. Soon, our time here will come to an end, and we will head back to Kiel, Germany, to work on our data. We will be sad to say goodbye to all our colleagues and friends here, and we hope that the smell of fish will not be the only impression we leave behind!

Soundscapes in the pearl of the orient seas: The Philippines!

It all started with a bang – several million years ago. Beneath the Atlantic, successive eruptions raised an enormous volcanic mountain from the ocean floor, and its very tip now forms rugged cliffsides, deep red canyons and fertile ground for hotel chains. How land was formed here, in the middle of the ocean, is still plainly evident in the red and black banded mountainsides of Madeira, in pools of volcanic rock frozen mid-flow and in cliffs sculpted by magma, wind and water. Life clings to this volcanic ground with stubbornness: Cacti climb sheer ridges, while sage-green, brown and vibrant yellow shrubs crouch against the rugged terrain.

Today, Madeira is known as the Island of Flowers, an image that echoes across postcards, signs and souvenirs. Indeed, many of the winding mountain roads are lined by eucalyptus trees from Australia, tall white and lilac lilies from South Africa, and hydrangeas from Asia. Fitting for an island that lives from tourism, while also beginning to buckle under its strain.

Our own project looks, at least partly, at another, less visible invader: human-made sound. Beneath the ocean’s surface, boat engines add to the island’s natural underwater soundscape, and during the six months we spend here we want to find out whether sound changes where the larvae of marine sessile animals, such as bryozoans, tunicates or polychaetes, choose to settle. Those animals are sessile in their adult life, but as larvae they are free floating. In this stadium, they are influenced by a wide variety of environmental factors—including noise—while they seek out a suitable habitat in which they could settle and survive.

And with that “Óla” from Team Madeira. We are Elin and Jana, two German students who have come to Madeira for half a year to take part in this year’s GAME (Global Approach in Marine Ecology) project.

Jana studies biology at the Ruhr-University in Bochum. “I was always interested in marine biology and had already worked in this field for my bachelor’s thesis. When I decided that I didn’t want to move away from Bochum for my Masters, I was a little bit sad, deep down, thinking that I couldn’t continue to pursue marine biology. So, I was thrilled to return to the ocean and to fieldwork when I got accepted for GAME”.

Elin studies biological oceanography in Kiel “This year’s GAME topic of The influence of soundscapes on hard bottom community colonization seemed made for me, since I had already written my bachelors thesis about the colonization of hard substrates and if I could’ve picked any field, sound would have been it.”

This year is the first time that GAMIEs are working with sound, which made the planning phase in Kiel in March extra exciting for us. We tested underwater microphones, so called hydrophones, tried out speakers and had many, many, many discussions about scientific literature and the experimental setup. In the end all teams agreed on one basic concept: One student in each country would analyze the effects of boat noise and the other the influence of natural soundscapes on the formation of invertebrate communities. Natural soundscapes will be captured by deploying thydrophones in underwater habitats that are typical for the marine region a team is working in. In Madeira, the underwater world is strongly shaped by the past volcanic activity, and features steeply sloping rock faces and rocky areas that are overgrown with algae and sessile animals. These form the most typical habitat of the region. Furthermore, here and there they give way to sandy bottoms at greater depths.

We are investigating the settlement under the influence of natural sounds, because more and more marine habitats have been destroyed by human activity. In the past, several studies have been conducted on marine mammals, fish, shellfish and coral species, which found that when sound was used to simulate healthy habitats in otherwise disturbed environments, it led to the successful re-establishment of populations. A concept that is known as acoustic restoration.

In our experiments, both, the natural sounds and the boat noise, will be played back from speakers and will be directed onto plastic plates hanging in the water, to which the larvae of sessile animals can attach.

So much for the theory.

After arriving on Madeira in early April, we got to work and realized quickly that reality is lots of planning, glue, trips to the hardware store and starting over. Luckily, we have kind and helpful supervisors at MARE, the research institute here in Madeira, many of which are former GAMIEs. They contributed their experience, advice and occasional emotional first aid. But most of the time we’re trying to do as much as we can on our own – with special support from Jana’s electronics-technician-husband, Niklas, who also came along to Madeira and is of great help with all the equipment. Even though we had many long and a few frustrating days, it was nice to plan and build everything on our own. Actually, it’s incredibly rewarding to see the finished results of our work running smoothly while the experiments are going on.

Our workplace here in Madeira is the marina in Quinta do Lorde, which is almost on the eastern tip of the island. It’s a beautiful workplace, because most days the water is calm and clear and we get to see sepias, triggerfishes and a school of barracudas swimming in the shallow waters. This makes it all the more frustrating that it is forbidden to go in, due to the ship traffic – you can imagine how hard it is for two marine scientists to follow this rule, and how often we stare into the water longingly.

The ideal way for us to run the two experiments was conducting them both at the same time. But of course, the playbacks of the natural soundscape and the boat noise shouldn’t mask or overlay each other. And they should not reach those panels that we have to study invertebrate settlement in the absence of any playbacks. This prerequisite is called acoustic isolation: whatever happens near one speaker shouldn’t affect the other settlement plates. Since sound can travel far under water, we choose the two opposite ends of the marina and two jetties in between for the deployment of the settlement panels.

Unfortunately, our workplace is in a busy marina and to check if the play-backed boat noise doesn’t affect the other locations where we placed settlement plates, we need silence throughout the entire area. So, we had to stop and redo the measurements many, many times, because of incoming and departing boats, loud wind, cracking noise from the jetties or technical difficulties with our hydrophones.

We had one truly frustrating Friday afternoon when we wanted to test acoustic isolation but couldn’t get even five minutes of silence without a boat engine in the background for hours! And then, shortly before we had to catch the last bus home, we finally managed to do the test- and it was perfect. We had recordings without any disturbances and we had acoustic isolation- which meant we could run both experiments in parallel.

Then the wind blew the hydrophone from the jetty into the water, while we were packing up. Jana was over it and ready to give up, but Elin declared it the best thing that had happened that day. She had in the morning naively predicted a short workday with plenty of time to go snorkeling. Instead, she got special permission to go into the marina just this once – and gleefully fished out the hydrophone. Everything was done just in time before the last bus came and we decided never to test acoustic isolation on a Friday afternoon again.

Since Jana studies the effects of natural soundscapes on larvae settlement, she needs to record the marine ecosystems of Madeira. The team at MARE helped her to choose a few promising locations, which best reflect Madeira’s rocky underwater landscape. They are in protected areas and have little boat traffic.We built six hydrophone stands, of which one was placed at each location with the help of a technical diver. The stands were constructed in a way that the hydrophone could be attached and detached by freediving from the surface, and this allows us to work independently of the diver. And, of course, to have the opportunity to go snorkeling for work :). For the first month it was just Elin who could hold her breath long enough to reach the hydrophone stand, which was in 5 to 8 meters water depth, because she had years of experience. But after training freediving while snorkeling in beautiful locations all over the island, first Niklas and then Jana figured it out and now we can divide this very popular task among the three of us.

Even when the project is running smoothly, there are always a million little things to think of, to plan and to organize. Our motto became ‘at least one of us is thinking’ – because of how often one of us forgot something or didn’t think ahead and the other one caught it just in time. And there is something to it. Even though we will write separate Master theses, we share the work and the responsibility, and it is amazing to work in a team in which you can truly rely on the fact that the other person cares just as much and is right there with you.

When we’re not in the workshop building our frames or glued to the binocular during long sampling days, we love to be in the water for snorkeling trips or go hiking in the beautiful mountains. The island’s nature is fascinatingly versatile, and after almost 5 months have passed now, we’re sure that we’ll never grow tired of the amazing views. There are so many Levada trails with waterfalls, hidden paths through the mountains and small towns to visit. Levadas are man-made irrigation channels on Madeira. They carry the water from the mountains from the north to the south. The network, which spans a total of 2,000 to 3,000 kilometers, is used today not only for agriculture but primarily as a world-famous hiking trail. We make a point to go exploring new places, but the joy of staying for half a year is that you get to find your favorites and come back to them.

We are really happy to have worked and lived here on Madeira, and we can’t believe that half a year has almost come to an end; we’d do it all over again in a heartbeat.

Team Madeira – At least one of us is thinking