Offshore drilling platforms extend the search for oil to the ocean's continental shelves—those gently sloping submarine regions at the edges of the continents.
They suffer from being heavier than conventional derricks and consequently are not usually found in offshore environments, where weight is more of a concern than in land operations.
The oceanic volcanic islands and their hot-spot trails are thus especially useful for geologists because they record the past locations of the plate over a fixed source.
As the ocean warms, a body of water called the Antarctic Polar Front—an upward movement of nutrient-rich sea that supports a huge abundance of marine life—is being pushed further south.
The geologic story the Opportunity read there always spoke of an ancient martian wasteland of windblown dunes pocked by the occasional acid-laced puddle.
To make calculations manageable even by computers, most of the models suppose either that the oceans are a motionless swamp or that they don't exist at all.