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Comment: 11:53 - 13:06 (01:13)
Source: Annenberg/CPB Resources - Earth Revealed - 4. The Sea Floor
Keywords: subduction, "Grand Canyon", vessel, instrument, "camel-grab", "box corer", "James Sadd"
Our transcription: Subduction begins at enormous underwater trenches, some of them several times deeper than the Grand Canyon.
Because of the great depth, marine geologists have had to come up with a host of ingenious ways of exploring the deep sea floor.
The primary tool used by Earth scientists to study the ocean floor is a research vessel like this one, outfitted with a variety of oceanographic sampling instruments.
Mounted on the stern of the vessel, is this A-frame, which is a hydraulically movable rack used to lift and deploy the instruments.
The oceanographic sampling instruments are tethered to the vessel with this steel cable wound around a revolving drum.
Scientists can take a bite of sediment or rock from the ocean bottom using a sampling instrument like this "camel-grab".
It takes sediment samples very quickly but only of the upper few centimeters of ocean bottom.
Often times, an undisturbed sample of the deeper layers is required to examine variations in the accumulated sediment on the ocean bottom with time.
This "box corer" takes an entire column of sediment, which later can be split open and the individual layers analyzed like pages in a book.
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