There are several different ways that we can find gas hydrates in the sediments under the ocean. The most commonly used technique for finding gas hydrates is collecting seismic data. Seismic data uses sound waves to create an image of the sediments beneath the ground. It can be used on land and at sea, but here we will talk about collecting seismic data at sea. To collect seismic data at sea, a ship travels along towing a sound source (like a large speaker) and a series of hydrophones, which listen and record the sound waves that are reflected off the seafloor and the sediment layers under the seafloor. The sound waves reflect, or bounce back, like an echo when you shout in a big empty room. We can use the reflected sound waves to build up an image of the layers of sediment below the seafloor, by measuring how long it takes for the sound waves to travel down, be reflected, and travel back to the hydrophones. Depending on the type of sediments being imaged, we can gather data from as deep as several kilometers beneath the seafloor.

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