A Deep Dive into Monterey Canyon, California’s Great Abyss

Standing in Moss Landing, a small coastal town known for its fishing fleet, busy harbor, and the twin smokestacks of its power plant, it’s hard to imagine that just offshore lies one of the most dramatic geological features on the West Coast, hidden beneath the water. I’ve been to the town many times (Phil’s Fish Market & Eatery is no longer there, unfortunately, but The Power Plant Coffee is nice), and I always enjoy how quiet and old-fashioned it feels, like a glimpse of California from 30 years ago. Most people passing through probably have no idea that beyond the harbor, the seafloor suddenly drops away into a vast underwater canyon.

Monterey Canyon is one of the largest submarine canyons on Earth. It stretches roughly 95 miles into the Pacific and plunges more than 11,800 feet at its deepest point. In scale it rivals the Grand Canyon, but almost all of it lies out of sight beneath Monterey Bay.

Monterey Canyon’s immense scale is the result of millions of years of underwater erosion. Powerful turbidity currents, dense flows of sand and sediment racing down the continental slope, have slowly carved the canyon and carried its debris far into the deep Pacific. One prevailing theory how it formed is that the canyon began as a river channel carved by the ancestral Salinas River, which carried sediments from the ancient Sierra Nevada to the ocean. As sea levels fluctuated during ice ages, the river extended further offshore, deepening the canyon through erosion. Another idea points to tectonic activity along the Pacific Plate as an important influence. Movement along nearby faults helped shape the seafloor and surrounding landscape, while gradual sinking of the continental shelf allowed sediment to collect and periodically cascade down the canyon into deeper water. These forces, combined with powerful turbidity currents, underwater landslides of sediment-laden water, worked in tandem to sculpt the dramatic contours we see today.

While the geology is awe-inspiring, the biology of Monterey Canyon makes it a living laboratory for scientists. The canyon is teeming with life, from surface waters to its darkest depths. Near the top, kelp forests and sandy seafloors support a wide variety of fish, crabs, and sea otters, while the midwater region, known as the “twilight zone,” is home to bioluminescent organisms like lanternfish and vampire squid that generate light for survival. Lanternfish use bioluminescence to attract prey and confuse predators, while vampire squid use light-producing organs to startle potential predators or escape into the deep. In the canyon’s deepest reaches, other bizarre creatures thrive in extreme temperature and pressure, including the gross-looking Pacific hagfish and the bizarre gulper eel. Some communities around cold seeps on the seafloor are sustained by chemical energy (chemosynthesis). Microbes feed on methane and other chemicals seeping from the sediments, supporting ecosystems of clams, bacterial mats, and, occasionally, tube worms.

The barreleye fish, captured in stunning video footage by MBARI, is one of the canyon’s most fascinating inhabitants. This deep-sea fish is known for its domed transparent head, which allows it to rotate its upward-facing eyes to track prey and avoid predators. Its unique adaptations are a dazzling product of evolution in deep water conditions, and only in recent decades have we developed the technology to explore the ocean this way and see these animals in their natural environment.

The canyon’s rich biodiversity depends on upwelling currents that draw cold, nutrient-rich water to the surface, triggering plankton blooms that sustain a complex food web. This process is vital in California waters, where it supports an astonishing array of marine life, from deep-sea creatures to surface animals like humpback whales, sea lions, and albatrosses.

What sets Monterey Canyon apart is the sheer accessibility of this underwater frontier for scientific exploration. The canyon’s proximity to the shore makes it a prime research site for organizations like the Monterey Bay Aquarium Research Institute (MBARI). Using remotely operated vehicles (ROVs) and advanced oceanographic tools, MBARI scientists have conducted groundbreaking studies on the canyon’s geology, hydrology, and biology. Their research has shed light on phenomena like deep-sea carbon cycling, the behavior of deepwater species, and the ecological impacts of climate change.

They recently developed this animation, the most detailed ever created of Monterey Canyon, to show what it looks like below the surface. It combines ship-based multibeam data at a resolution of 25 meters (82 feet) with high-precision autonomous underwater vehicle (AUV) mapping data at just one meter (three feet), revealing the canyon’s intricate underwater topography like no one has ever seen before.

MBARI’s founder, the late David Packard, envisioned the institute as a hub for pushing the boundaries of marine science and engineering. Researchers like Bruce Robison have pioneered the use of ROVs to study elusive mid-water and deep-sea animals, capturing stunning footage of animals like the giant siphonophore, a colonial organism that can stretch over 100 feet, making it one of the longest animals on Earth.

Among the younger generations of pioneering researchers at MBARI, Kakani Katija stands out for her groundbreaking contributions to marine science. Katija has spearheaded the development of FathomNet, an open-source image database that leverages artificial intelligence to identify and count marine animals in deep-sea video footage, revolutionizing how researchers analyze vast datasets.

Two leading scientists at MBARI, Steve Haddock and Kyra Schlining, have made groundbreaking discoveries in Monterey Canyon, expanding our understanding of deep-sea ecosystems. Haddock, a marine biologist specializing in bioluminescence, has revealed how deep-sea organisms like jellyfish and siphonophores use light for communication, camouflage, and predation. His research has uncovered new species and illuminated the role of bioluminescence in the deep ocean. Schlining, an expert in deep-sea video analysis, has played a key role in identifying and cataloging previously unknown marine life captured by MBARI’s remotely operated vehicles (ROVs). Her work has helped map the canyon’s biodiversity and track environmental changes over time, offering important clues about how human activity is affecting the ocean and how marine ecosystems respond.

Monterey Canyon draws scientists from around the world. Its deep, steep walls and easy access from shore make it an ideal place to test new technologies, from autonomous underwater vehicles to instruments that track subtle changes in ocean chemistry. The canyon also feeds into a larger culture of ocean exploration here, with places like the Monterey Bay Aquarium helping translate what scientists discover in the deep into stories the public can see and understand.

As scientists push deeper into Monterey Canyon, right off our own coast, each expedition reveals something new. Strange animals, shifting sediments, and clues about how this hidden world works. But the more we learn, the more questions emerge about how life survives in the deep and how human activity may be changing it. With every dive, the canyon reminds us how much of the ocean remains unexplored.