Oceanography is the study of the Earth's oceans. Toward the end of the 19th century the Challenger, a British ship, became the first research ship to use relatively sophisticated measuring devices to learn about the oceans. The tools used by scientists have grown over the years to include sonar, floats, satellites, submarines, and computer technologies.
Several clues point to oceans existing almost since the beginning of the planet. Scientists date the earth at 4.56 billion years old from rocks in sediments nearly that old in water. Ancient lava flows are another clue. When lava flows have a distinct glassy crust this indicates the lava was cooled rapidly underwater. Other studies of radioactive elements prove water to be abundant throughout Earth's history.
Oceans provide moisture and heat to the atmosphere and influence large-scale circulation patterns. The ocean is also a vast reservoir for carbon dioxide - but this is best left for another blog update.