Ask an Explorer

The Hudson Canyon team received questions throughout the expedition. Selected questions and answers appear below.

From Saratoga Lake, NY:
Where does the Hudson River begin, and how deep is the Hudson Canyon?

The Hudson River begins in upstate New York, just south of Mount Marcy in Lake Tear of the Clouds. The Hudson Canyon is 300 mi long, and at its deepest, seaward point is about 20,000 ft deep. -- Dr. Peter Rona, Rutgers University, and Tom Bolmer, Woods Hole Oceanographic Institution

From Deville, LA:
If you have some rough weather for 3 or 4 days and have to suspend surveying for that length of time, will you have to extend your trip?

This is an interesting and timely question with the impending tropical storm Gustuv just south of our survey area. The schedules of NOAA vessels are predetermined and locked. Unfortunately, bad weather results in lost surveying time. -- Dr. Peter Rona, Rutgers University, and Tom Bolmer, Woods Hole Oceanographic Institution

From San Antonio, TX:
When the radar goes down to the bottom of the ocean floor to see the depths, can it tell the difference between something lying on the sea floor and the actual bottom of the ocean? Is it the same kind of technology used for finding shipwrecks at the bottom of the sea?

Actually, radar cannot go down to the bottom of the ocean. Because radar is an electromagnetic wave, it gets quickly absorbed in the surface waters of the ocean. Instead, oceanographers use sound waves, known as "pings," to help them "see" the bottom of the ocean. The sound waves that we are using to tell the depth of the oceans, and hence topographic features, are not the same waves that are used to see something that is lying on the bottom.

To find shipwrecks at sea, oceanographers use bottom cameras, remotely operated vehicles (ROVs), and a technique known as sidescan sonar. This is similar to sea-floor mapping, but instead of sending a ping straight down, it sends pings out to the sides. Any objects encountered by the pings reflect them back to the ship. Objects sloping toward the sidescan are identified as being closer because the pings encounter them first and thus, return to the ship first. The data received back at the ship is corrected for "slant angle." Objects are seen as images in grayscale (shades of gray) and not as topographic lines or contours. -- Jim Robb, U.S. Geological Survey, Woods Hole, MA, Field Station

From Kennett Square, PA:
I'm wondering about your course. How many days will it take you to get to the Hudson Valley site, and will you be extending that travel portion to gather data or will you "hurry up and get there" to do your study? How many days will you spend weaving around doing sea-floor mapping, and how much time will you spend sampling once you get there?

It took about three full days of sailing to get from the dock in Miami to the location on the Hudson Canyon site where data collection began (See August 31 Log). The expedition team did “hurry up to get there” because a priority area for mapping had been predetermined, and it would take about 15 days to map this area, not accounting for weather-related delays. Sampling, such as the water-column samples collected with the CTD rosette, takes about 3 hrs, all "sitting on station" (remaining in the same spot) and at least five of these sample collections are planned. In addition to sample collections, researchers send down a current meter once in a while so that the data can be corrected for ocean velocity. This, too, takes time. Sampling will take about 24 hrs of the total mapping time. -- Lisa Weiss, Jacques Cousteau National Estuarine Research Reserve

(top)