Overview:
The Mariana Trench — the deepest place on Earth and a defining feature of the Pacific — is now at the center of a controversial Trump-era proposal that could open nearby waters to deep-sea mining. Scientists warn the plan risks irreversible damage to marine ecosystems, migratory species and island communities, raising urgent questions about why one of the world’s most iconic ocean regions is being targeted at all.
By Andrew D. Thaler
WASHINGTON, 22 DECEMBER 2025 (SAN FRANCISCO CHRONICLE) — Can you name a single geologic feature of the deep sea?
Take a moment. Think about it.
Did you pick the Mariana Trench? Odds are pretty good that you did. It is the deepest point on our planet and one of the few places in the deep ocean that most people have heard of.
The Mariana Trench is not just an isolated spot on the seafloor. This 7-mile-deep column extends into sunlit waters and stretches over 1,500 miles, from Farallón de Pájaros, the northernmost island of the Marianas, to Guam. The geologic structures that make up the trench include the subduction zone, where the Pacific Plate sinks beneath the Mariana Plate at a rate of 1 to 3 inches per year; basins to the west of the trench, where the ocean’s crust buckles and cracks, creating chains of volcanic islands, and an eastern basin, where the Pacific crust is stretched and deformed as it is dragged into the trench, creating a complex network of seamounts and abyssal plain.
The trench lies largely within the U.S waters of Guam and the Northern Mariana Islands. More than 200,000 people live on its edge.
On 12 November, the Trump administration put out a request for information about the mineral resources in the basin east of the Mariana Trench. This is the first step in a process that could eventually open the region to deep-sea mining — an emerging industry with a half-century history of false starts and failed attempts to reach commercial production.
It targets small cobblestones called polymetallic nodules that form on the deep abyssal plain. Large, tracked crawlers or autonomous robots collect these nodules, which are then carried to the surface in a hopper or pumped up to a ship through a riser and lift system. Also targeted are dense, metal-rich ferromanganese crusts, which form on the sides of seamounts. Ferromanganese crusts are mined in a process similar to mountaintop removal, where thick crusts are stripped from the seamount, ground into fist-size chunks and pumped to the surface. Both nodules and crust are rich in cobalt, nickel and manganese, three critical minerals that play a key role in the renewable energy transition.
The leading proposals call for a dewatering plume, where deep, ore-contaminated water from the surface vessel is released into the midwater.
Ocean scientists are only beginning to understand how deep-sea mining can impact seafloor ecosystems. But early deep-sea experiments give us rare glimpses. Fifty years on, scars left by mining tools persist and the animals that built and defined these deep-sea ecosystems haven’t recovered. We know far less about how the industry will alter the water column. Recent studies have shown that the mid-water plumes produced by some deep-sea mining technologies could collapse marine food webs. Large, migratory predators, including sharks and commercially important billfish and tuna, depend on the mass of midwater prey that migrate to the surface to feed.
Whales, dolphins and turtles, which migrate through and feed in the Marianas, are vulnerable to ship strikes. The proposed mining area is lightly trafficked now, but a full-scale deep-sea mining operation will involve dozens of ships transiting through the area to deliver supplies and personnel and offload ore. Critically endangered hammerhead sharks are particularly abundant around seamounts, where they aggregate to feed and reproduce.
For whales and dolphins, the noise produced by deep-sea mining is an addition to the ocean soundscape. Deep-sea mining produces a continuous drumbeat as ore is pumped through the riser and lift system; the noise can exceed 120 decibels — far above natural levels, approaching the volume of a jet engine during takeoff. That sound will be constant throughout the life of the mining operation, impeding marine mammals’ ability to navigate and communicate.
The impacts of deep-sea mining on coastal communities are even less well understood. The Clarion-Clipperton Zone — an area of the Pacific between Hawaii and Mexico where the majority of impact studies have been conducted — lies far from human habitation. The Mariana Trench region is much closer to the inhabited islands of the Northern Marianas and Guam, where mining operations could come in direct conflict with commercial and artisanal fisheries. The prevailing currents of the region could potentially carry mining plumes into the island chain.
What is curious about the Trump administration’s request for information is that, until early November, no one involved in the industry was seriously discussing the area around the Mariana Trench. While the eastern Mariana basin is in an optimal zone for crust formation, ferromanganese crust mining is the least mature of the deep-sea mining industries, and no U.S mining company has developed a ferromanganese crust mining tool. The region is less than ideal for nodule mining, with a complex and varied seafloor that is unlikely to have the vast, dense fields of nodules seen in places like the Clarion-Clipperton Zone. There are no known commercially viable nodule fields within the proposed area.
I am not an absolutist when it comes to the development of deep-sea mining. The industry is rich with potential and peril. Right now, the most compelling argument working to deep-sea mining’s advantage is that this is the first major extractive industry for which environmental concerns have preceded commercial exploitation. It presents a rare opportunity to get things right, provided we do not preemptively launch a hasty race to the seafloor.
Even still, I can think of no worse place to begin than in the area surrounding the Mariana Trench. Beyond the lack of proven commercially viable ores, the immaturity of crust mining technology and the potential to harm marine life important to the people who live on the edge of the trench, it would be a foolhardy move for an industry in its infancy to mine the only feature of the deep ocean that everyone recognises…PACNEWS
Andrew D. Thaler is a deep-sea ecologist, conservation technologist and ocean educator. He is a Public Voices Fellow on Technology in the Public Interest with the OpEd Project.