The invention of sonar changed the way that the seafloor is mapped. A combined transmitter and receiver , called a transducer , sends a sound pulse straight down into the water. The pulse moves down through the water and bounces off the ocean bottom. The transducer is able to pick up the reflected sound. Computers precisely measure the time it takes for the sound pulse to reach the bottom and return.
The depth of the ocean is calculated by knowing how fast sound travels in the water approximately 1, meters per second. This method of seafloor mapping is called echosounding. Echosounders can use different frequencies of sound to find out different things about the ocean.
Water depth is typically measured by echosounders that transmit sound at 12 kiloHertz kHz. Lower frequencies 3. Higher frequencies kHz can be used to identify fish and plankton that are in the water column See Fishing. Search for:. Home Science of Sound Sound What is sound?
How do you characterize sounds? Amplitude Intensity Frequency Wavelength How are sounds made? What happens when sound pressures are large? Sound Movement How fast does sound travel?
Why does sound get weaker as it travels? Sound Spreading Sound Absorption How does sound move? Reflection Refraction Scattering Reverberation How does sound travel long distances? Sound Measurement How is sound measured? What units are used to measure sound? How are sounds viewed and analyzed? How is hearing measured? What sounds can people hear? What sounds can animals hear? Sounds in the Sea What are common underwater sounds? How does sound in air differ from sound in water?
How do people and animals use sound in the sea? Why do sounds have certain properties? This measurement for the deepest point - known as Challenger Deep - is arguably the most precise yet. This instrument allows you to map a swath of soundings perpendicular to the line of travel of the ship. It's like mowing the grass. And we were able to map the trench at a m resolution," he told BBC News. The distance to the bottom of Challenger Deep has an error associated with it of about plus or minus 40m.
The figure of 10,m is slightly less than some other measurements in the modern era, but they are all broadly similar. A location in the trench about km to the east of Challenger goes almost as far down. Dr Gardner said his team's survey put a huge effort into getting the "sound speed profile" of the water column correct - this measure of how the echosounding signals curve as they descend is the largest source of error in the measurement.
He presented the results of the mapping here at the American Geophysical Union AGU Fall Meeting , the world's largest annual gathering of Earth and planetary scientists. The US State Department funded the study because it wants to know whether the exclusive economic zone encompassing the American territories of Guam and the Northern Mariana Islands can be pushed out beyond its current limit of nautical miles km. This may be possible if the shape of the seafloor fulfils certain requirements under the United Nations Convention on the Law of the Sea.
But the data also has high scientific interest in that it gives geologists a clearer picture of the structures in one of the most fascinating subduction zones on Earth.
It is at the trench where a huge slab of Pacific oceanic crust is diving down under the adjacent Philippines tectonic plate. Researchers are keen to know what happens when underwater mountains, or seamounts, go over the edge and are swallowed.
There has been considerable debate over whether the descent of the seamounts can influence the frequency and scale of big earthquakes. It has been suggested they might create extra friction that can then be released suddenly to trigger major tremors.
That crust is really brittle. Always check your chart to see water depths. Sonar is used. Find more answers Related Questions. The greatest known depth of the ocean is 35, ft. What instrument measures perimeter? A tape measure is an instrument that measures perimeter. You can use a scale to measure milligrams, centigrams, grams, and small numbers of kilograms. When measuring small amounts of capacity, you can use a graduated cylinder. Graduated cylinders can measure milliliters and centiliters.
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