Ocean drilling or the probing of the sea floor is an important method used by oceanographers to learn about seas and sea life. In the early years of ocean science, the scientists dredged and collected sediment samples from the ocean floor because they did not have drilling technology and could not collect any samples from very deep parts of the ocean. This changed in 1968 when the US National Science Foundation established a sea floor drilling program. It was originally intended to study plate tectonics. For the next twenty-five years the Deep Sea Drilling Project (DSDP) collected cores from the ocean floor. The cores were sediment and rock in long cylinders, several meters in length and only a few centimeters in diameter. This was accomplished with pipes many thousands of feet long with drills at the end.
Again, the cores were meant to be a means to study spreading from plate tectonics. The cores provided valuable information for that field and they ultimately revealed much more. Ocean cores can provide information about climate change and the evolution of the earth to marine geologists, paleoclimatologists, and other scientists. The cores, because they have been resting quietly on the bottom of the ocean, have been more preserved than the rocks on land that geologists study for the same clues.
In 1985 a new drilling project, the Ocean Drilling Program (ODP), began as a result of the success of the DSDP, and it focused more on the breadth of information that ocean cores can provide. Sea floor drilling continues today with more advanced technology and drills that can reach even greater depths. Now, when cores are drilled they are divided in half, one half to be studied in the laboratories of the drilling ships and the other half is sent to a core library. There are numerous core libraries around the world where marine geologists and other scientists can go to look at different ocean cores.
Ocean cores, like rock formations on land, are composed of layers of sediment. Often, ocean cores feature more continuous sedimentation than continental samples. There are fewer gaps and conclusions can be drawn about the ancient world from smaller samples, using the same dating methods. Rock morphology and mineral composition are examined, just as with land samples. From ocean cores, scientists have learned about large climate shifts, and changes in temperature and precipitation that have occurred in the past. The locations the cores are drilled from indicates regional differences and other paleoclimate evidence.