Imagine tripping over a throw rug. Now consider it, lying rumpled, piled up across the floor. This is what the geography off the coast of California would look like, if we could drain away the water.

Normally, a continent's margin includes a continental shelf, which is a broad, flat expanse, sometimes stretching for hundreds of miles off the coast. But in California, where tectonic forces have stretched and distorted rock as if it were made of Silly Putty, we have instead a tangle of deep basins and shallow ridges, folded and crumpled like our rug.

Understanding these regions and the forces that produced them are of vital importance to scientists, as millions of people call Southern California home. These same forces can trigger monstrous earthquakes and tsunamis; this dynamic stretch of coast and its inhabitants and economy are vulnerable.

We may not have the power to halt the forces at play here, but understanding them can help us to make better predictions and preparations for when they wreak havoc.

After making several dives off the coast of San Diego, we ventured further north, and prepared for three dives near Santa Catalina Island. The first was on Kimki Ridge. Kimki Fault hugs its west flank, and its 200-meter-tall existence is due to the pressure produced by creeping tectonic plates. We expected to find evidence of geologic activity, and perhaps active methane seeps at three locations along the crest.

Think back again to the imaginary rug, and picture lighter-than-water hydrocarbons migrating upward into the folds, and then oozing out under pressure, and you've got a pretty good mental image of the methane seeps.

As we dove on Kimki, we were looking for gray or white clumps of bacterial growth, and a variety of organisms that had evolved to take advantage of this unique deep-sea food source.

In a place that is eternally dark, cold and under tremendous pressure, life takes on some extraordinary characteristics. Creatures evolve without eyes, with strange sensory systems and bizarre methods of feeding and communication.

Coming upon our first methane seep, we found piles of dead white clams.

'We're getting close,' announced Milene Cormier, our science lead.

A few meters further, we observed a cluster of live clams, their hinges facing upward so their openings could face down into the flow of methane.

This way the symbiotic bacteria living within their tissues could take this toxic (to us) chemical and use it to create food. Thick, gray bacterial mats clung to the sandy floor in patches.

'Can we get a sample of the bacterial mat?' Cormier asked, and Jessica Sandoval, piloting the remotely operated vehicle Hercules, complied.

She used Herc's manipulator arm to pull out the vacuum tube, also called the 'slurp gun.' It was the end of only her first week piloting Herc, and it took her several attempts to get the tube positioned just right.

Sample collection completed, our watch finished slightly thereafter, the next watch taking over as we journeyed to our cabins in search of sleep.

The next dive was at Catalina Canyon. The vehicles descended to 1,310 meters, almost 4,300 feet, deep, and only rose about 200 meters in depth over the course of 12 hours, zigzagging back and forth across the canyon.

As before, organisms clung to rocky surfaces. Red crabs jealously guarded delicate white glass sponges, and eerie, eel-like fish glided out of the darkness. Expanses of sand and mud were left to brittle stars, urchins and the occasional flatfish or skate.

The third dive was on Catalina Island's northeastern flank.

The sun set behind the island as we prepared for our watch, casting peach and golden hues across the sky and water. Holding position alongside the island's steep and craggy shoreline, we could see the lights of Avalon starting to twinkle in the distance.

The vehicles descended through the water, ethereal dinner plate jellies dancing in the midwater between them, visible from the remotely operated vehicle Argus' view camera.

They reached the bottom quickly. It was the shallowest dive of the cruise.

The species here were dramatically different from those we had seen so far. Pink sea urchins littered the sea floor, and an abundance of lavender-colored skates hugged the sandy bottom.

But shallow is a relative term in deep sea exploration. It was still 150 meters or nearly 500 feet deep. At this depth, there was about 215 pounds of pressure per square inch, the temperature was only a few degrees above freezing, and we hovered just at the edge of the twilight zone, a place so dark that no photosynthesis could occur.

We came across a pile of pinkish round objects, clustered together in a sandy hollow. They were some kind of mollusk, probably a clam.

They looked like walnuts, and snapped close as we watched on the monitors. But we could not come up with an immediate identification, so we collected a few of them. Sandoval maneuvered the manipulator arm with dexterity and grace, no small feat for a robotic arm with a gripping strength of 600 pounds per square inch.

Later, when the animals were brought up on deck, it was revealed that their shells were incredibly delicate, making this even more marvelous!

Toward the end of the dive, as I watched from the lounge, the team finally came across a paleo shoreline, a submerged remnant of a beach eons old.

Changing sea levels, and perhaps even a sinking island, could explain its submergence. Rounded rocks and thick layers of broken shells heralded its presence.

I marveled at the diversity of the habitats we had visited thus far, the remarkable adaptations their creatures displaying.

Every inch, even the seemingly deserted muddy bottom, was densely populated. There is so much of it left to explore, and the more we explore, the more questions I have.

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