These are ways scientists learn about the deep ocean:
Here are some of the major features of seafloors:
Magnetic polarity is present within the seafloor. Using a magnetometer, scientists were able to plot symmetrical striped patterns using points of normal and reverse polarity. These patterns revealed that:
Seafloor Age: There have been four magnetic periods over time:
Older sediment is located further away from mid-ocean ridge crests and newer sediment is located closer to them. The oldest seafloor is less than 180 million years old. Characteristics of sediment as it progresses further away from ridge crest are described below:
Seafloor Spreading Hypothesis: Harry Hess designed this hypothesis by combining the ideas of Wegener’s continental drift hypothesis and Holmes’ mantle convection hypothesis. As lava rose to the surface, existing seafloor was pushed in opposite directions. Cooled lava then formed different stripes. Since magnetite crystals face the North Pole, the different stripes show the different ages of the seafloor. Therefore, each of the magnetic periods has its own layer of igneous rock with different magnetic polarity from the layers around it.
Hess also realized that the oldest oceanic crust must be recycled somehow because new oceanic crust is constantly being created but the Earth can’t get any bigger. He then came up with the following conclusions: