Voyage's Close Calls Produce Better Maps of Undersea Mountains

[Judi Lynn]

Voyage's Close Calls Produce Better Maps of Undersea Mountains
LiveScience.com livescience.com – Tue Mar 8, 5:50 pm ET

Our knowledge of the ocean floor has many gaps; maps based on satellite data contain only the roughest of details. A scientific cruise is using sonar to fill in the picture along its path from South Africa to Chile.

Since a U.S. Navy research vessel, the Melville, departed from Cape Town Feb. 20, geophysicist Joseph "JJ" Becker has been mapping underwater mounts as tall as 14,800 feet (4,500 meters), using a sonar system that bounces sound off the seafloor and analyzes the signal that returns.

The satellite data don't offer precise information about the height of seafloor mountains, so for the crew of the Melville, passing over them can be tense. In one case, the satellite data predicted the peak of a mountain would be 19.7 feet (6 m) below the surface. The ship draws almost the same depth. During the approach, Becker and the ship's captain carefully monitored the mountain below them on the sonar to make sure they weren't going to run aground. Meanwhile, someone else kept an eye out for rocks or shoals.

Even a sonar-detected depth of 984 feet (300 m) was cause for concern in the open ocean, where some spire could have gone uncharted. "In real life, this is a bit like driving your car toward a brick wall, calculating how many seconds it will take to hit the wall and being ready to slam on the brakes at the last minute," Becker told OurAmazingPlanet.

More:
http://news.yahoo.com/s/livescience/20110308/sc_livescience/voyagesclosecallsproducebettermapsofunderseamountains

[Orsino]

1. Bruised shins produce better map of living-room furniture. n/t