One of the most difficult environments for geologist to gather samples of rock and study geological features are the ocean floors. The vastness of the ocean in addition to the immense pressure makes traditional methods of collecting samples and viewing features nearly impossible. To combat this, geologists have developed tools and techniques to help them understand the hidden features of the sea. With water covering a majority of the planet it is important for scientist to be able to gather samples in order to get a complete picture of Earth's geological history.
Marine geology is the branch of geology dedicated to studying geological features impacted by the ocean. This includes the coast lines as well as features found deep on the ocean's floor. One method scientist use to study the ocean floor is visual observation. This is more difficult than on land however advances in technology such as submarines and other subversive craft have made it easier. Using submarines scientist can physically see the bottom which can help them get a better understanding of what the environment looks like. Clearly there are limitations to this process and sand and silt make understanding the composition difficult through visual analysis.
Having samples of a material allows scientist to see the layers of rock to better understand the process that created them. One way to do this is by getting a core sample that can be studied later. This process involves dropping weighting pipe to the bottom of the ocean floor and bringing samples back to the surface. Geologists are aware that the same forces at work on land are at work in the ocean as well. Samples of rocks help determine their composition allowing them to understand geological histories of the regions studied. A better method for getting core samples in a gravity corer. This drills into the ocean floor bringing a solid core up in the process.
Benthic Landers are a tool often used to gather chemical samples of material in the ocean. Typically used by marine biologist they can also be useful by geologist to detect chemical composition of the water and gather samples. They can then later be analyzed to see what processes are taking place in a particular region.
Gravimeters are a common tool used to determine the density of rocks along the ocean floor. This allows for scientist to determine the hardness of rock and detect liquids that are under the surface. It is used by both geologist and the oil industry to find deposits below the surface. It works by detecting magnetic forces and with them scientist are able to get an understanding of the internal forces at work within a rock bed.
Magnetometers are used to determine the magnetic fields within a rock. This is important to understand the metallic composition of rocks through the magnetic field they project. A key benefit to this equipment is that it helps scientist isolate particular objects in rock that they are searching for. Used in a variety of disciplines it helps gather understanding of composition with requiring a direct sample of the object itself.
Geologists rely heavy on seismic surveys to determine the properties on the ocean floor. By reflecting seismic waves off of the objects below, scientists are able to determine density and composition of the material below. In areas where it is difficult to reach these surveys are the best tools scientists have to determine what is truly below. These surveys provide a map of the area below and have been used to detect features that were once beyond observation and understanding.