1. Bathymetry
What lies beneath?

2. The Ocean Floor Is Mapped by Bathymetry
The discovery and study of ocean floor contours.

3. How did early scientists study the ocean floor?
Early measurements were made by making SOUNDINGS.
Sounding:
A simple method of finding the depth of the ocean using something heavy tied to a rope.
HMS Challenger

4. Advances in Bathymetry: Echo sounding
a method of measuring seafloor depth using powerful sound pulses.
Echo sounding is a method of measuring seafloor depth using powerful sound pulses.
The pulses of sound energy, or “pings,” from the sounder spread out in a narrow cone as they travel from the ship.
When depth is great, the sounds reflect from a large area of seabed. Because the first sound of the returning echo is used to sense depth, measurements over deep depressions are often inaccurate.

5. An echo sounder trace.

6. Advances in Bathymetry: Multibeam Systems
Multibeam sonar:
A high-tech version of echo sounding using as many as 121 beams of sound radiating out at up to 120º.

7. Multibeam transducer on a research ship.

8. Mowing the lawn…

9. Measuring the seabed from space.
Satellite bathymetry:
A very accurate method of mapping accomplished by bouncing 1000s of radio waves a second off of the ocean surface.

10. Multibeam vs. Satellite Bathymetry

11. Concept Check:
How was bathymetry accomplished in years past? How do scientists do it now?
Echo sounders bounce sound off the seabed to measure depth. How does that work?
Satellites orbit in space. How can a satellite conduct oceanographic research?