–By Christy Fandel, Coast Survey physical scientist
Have you ever wondered what lies beneath the charted soundings on a nautical chart? While surveying Alaskan waters during the 2013 hydrographic field season, collecting bathymetry to update NOAA’s nautical charts, hydrographers revealed many interesting geologic features on the seafloor.
NOAA focuses a significant portion of our ocean mapping effort along the Alaskan coast. The Alaskan coastline represents over 50% of the United States coastline and dated nautical charts are inadequate for the increasing vessel traffic in this region. NOAA surveys are essential for providing reliable charts to the area’s commercial shippers, passenger vessels, and fishing fleets.
This past season, NOAA-funded hydrographic surveys in Alaska revealed many interesting geological features on the seafloor. Three surveys, in particular, took place in southeastern Alaska in the Behm Canal, along the Aleutian Chain within the coastal waters surrounding Akutan Island, and around Chirikof Island.
These three areas were among the areas surveyed by the NOAA Ship Rainier and surveying contractor Fugro-Pelagos during the 2013 field season.
In May, hydrographic surveying conducted by NOAA Ship Rainier in the Behm Canal revealed two distinct geological features. In the northern region of the canal, scientists identified a long, meandering ancient river. This ancient submarine river is nearly 40 km in length with up to 50 m in relief. Further south, Rainier surveyed a large volcanic-like feature. The surveyed volcano appears to have a distinct caldera, or collapse-feature that most likely formed after the volcanic eruption.
Multibeam bathymetry of the northeastern portion of the Behm Canal shows a large, meandering submarine river. The cross-sectional inset highlights the relief of the channel, nearly 50 m, as shown by the red box.
Multibeam data acquired by NOAA Ship Rainier shows a large volcanic feature in the southern portion of the Behm Canal.
Directly following the Behm Canal survey, Rainier transited west to survey the coastal waters surrounding Chirikof Island. The acquired bathymetric data revealed a stark northeast-trending fault in the southeastern portion of the survey area. This surveyed fault is distinguished by a clear misalignment across the fracture.
The red box outlines the northeast-trending fault along the coast of Chirikof Island, shown with bathymetry acquired by the Rainier.
Concurrently, an Office of Coast Survey hydrographic surveying contractor – Fugro-Pelagos – was surveying off the western coast of Akutan Island. Fugro’s hydrographers identified a large volcanic feature within the acquired bathymetric data. The surveyed volcanic feature is believed to be either a volcanic vent or cinder cone volcano. The multiple circular rings outlining this feature may represent the successive lava flows that formed the volcano.
Multibeam bathymetry acquired by Fugro, around Akutan Island, shows a large volcanic vent or cinder cone volcano, marked by multiple circular rings that represent the successive lava flows that formed the volcano.
With the upcoming 2014 hydrographic field season quickly approaching, the number of geologic discoveries will only increase. Extending all along the Aleutian Chain, from Kodiak Island to Bechevin Bay, the planned surveys for the 2014 field season will surely reveal many interesting and previously unknown geologic features.
Cold Bay Elementary School students visit the NOAA Ship Rainier
On September 13, NOAA Ship Rainier began surveying Cold Bay, its fourth project of the summer. Cold Bay is a small town on the Aleutian Peninsula approximately 540 miles southwest of Anchorage, Alaska. The town currently has approximately 88 full-time residents and boasts an airport with one of the longest runways in Alaska.
On September 19, after deploying her launches for the day, officers and crew welcomed aboard the entire Cold Bay Elementary School – all eight students, teaching assistant Mrs. Lyons, and their teacher, Mrs. Burkhardt. The students are currently between fourth and seventh grade and go to school in a state-of-the-art, two-room school-house.
During the tour, the students learned about driving the ship and making nautical charts. They saw how sonars work, and they even used a sediment sampler to determine the seafloor composition.
The students were full of questions and enjoyed learning about life on a ship. They also captured the admiration of Rainier‘s commanding officer. “When Cold Bay residents describe their town, they can also boast of wonderful elementary school students who have a desire to explore new things,” explained Cmdr. Rick Brennan. “One of the great things about working on a NOAA ship is the opportunity to meet students like this. Combining our love of the sea with their enthusiasm for learning — that’s where America’s future hydrography starts.”
This student is ready to work!
The group examines bottom samples collected by the Rainier.
Cmdr. Rick Brennan explains how davits work.
- Cmdr. Brennan with friends — and potential future hydrographers.
In late May, NOAA Ship Rainier officially started her Chatham Strait hydrographic survey project in southeast Alaska. It’s often difficult to imagine the age of many of the depth measurements depicted on Alaskan charts, but this short animation brings it home.
The older picture is U.S. Coast and Geodetic Survey Steamer Patterson and her steam-powered launch Cosmos, surveying Gut Bay in 1897. (The USC&GS is one of NOAA’s predecessor agencies, and a direct predecessor of the Office of Coast Survey.) We juxtaposed Patterson with the Rainier, who is finally able to update the bathymetry — at the exact same location — 116 years later.
The Patterson was under the command of Lt. Cmdr. E.K. Moore, U.S. Navy, while Coast Survey assistants carried out the scientific work. In today’s Coast Survey, a NOAA officer — on the Rainier, it is Cmdr. Richard Brennan — is both commander of the vessel and its chief scientific officer.
The opening to Gut Bay is only about 100 yards wide – and it seems narrower!
“It must have been a real challenge to get the Patterson into this tiny bay in 1897,” Cmdr. Brennan observed. “The opening to the bay is only about 100 yards wide — and seems narrower than that when you are in the middle of it, since the cliffs rise almost vertically on either side.”
“We had the benefit of surveying the very narrow entrance’s seafloor with complete multibeam sonar coverage, and had the use of radar and GPS to inform us about our exact location as we made our way through the incredibly tiny opening into this bay. The Patterson (a steam powered sailing vessel) would have had to do this visually with only a few lead line soundings across the entrance. This must have made for an exciting navigational experience!”
Credit for photo of Rainier: Ensign Damian Manda
NOAA Ship Rainier is due to arrive at its homeport in Newport, Ore., on November 1, completing the ship’s 2012 hydrographic survey season. (Watch Rainier’s progress on NOAA’s Ship Tracker.) This survey season, Rainier departed Newport on May 17 and spent her summer mapping 604 square nautical miles of the ocean floor in Alaska, stretching from Kodiak to the Shumagin Islands, along the Alaskan archipelago.
Rainier has a long 1,769 nautical mile trip back to homeport in Newport, Oregon.
“We completed our last survey on October 24, and began the long 1,769 nautical mile trip back to Oregon,” said Rainier’s commanding officer, Cmdr. Richard Brennan. “The crew put a lot of great effort into their work, some of it under challenging weather conditions.”
Rainier and her four smaller survey vessels use multibeam echo-sounders to measure the depth of the ocean along her path, collecting millions of measurements. More than half of the area surveyed by Rainier this summer had never been surveyed before, leaving large sections of nautical charts void of ocean depth measurements. Commercial shippers, passenger vessels, and fishing fleets need updated charts, which NOAA’s Office of Coast Survey will produce with the multibeam’s precise and accurate measurements.
“Simply put, we have better maps of the moon than of our oceans,” said Rear Adm. Gerd Glang, director of Coast Survey. “Much of our knowledge of U.S. coastal seafloors dates from eras when ocean commerce was more limited, especially in Alaska.”
“At a time when Alaskan waterways are facing unprecedented demands from maritime commerce, Rainier is acquiring the data for navigational charts that are the foundation of the marine transportation system,” Glang explained.
The 231-foot Rainier, one of the most modern and productive hydrographic survey platforms of its type in the world, is named for Mount Rainier, a massive volcanic cone rising 14,410 feet above sea level in Washington. At the time the ship was commissioned, in 1968, vessels of this class were named for geological features. Rainier underwent a major repair period from Nov. 2009 to Jan. 2011, when new systems and equipment were installed.
The ship’s sophisticated seafloor mapping systems allow researchers to acquire hydrographic data that is used to update the nation’s nautical charts. Rainier carries four survey launches that survey shallow, near-shore waters.
Rainier’s scientists, survey technicians, NOAA Corps officers, and crew bring a wide range of navigational and hydrographical expertise to the mission. Rainier has a total complement of 52 people: 12 NOAA Corps commissioned officers, 11 engineers, 14 deck/boatswains, 9 hydrographic survey technicians (in addition to the officers, who are all hydrographers), four stewards, and two electronic technicians.
The ship is part of NOAA’s fleet of research and survey ships operated by NOAA’s Office of Marine and Aviation Operations.
One of Rainier’s projects for 2012 was four surveys in the Shumagin Islands, constituting 2083.2 linear nautical miles of survey lines, and 112.85 square nautical miles of seafloor – most which were never surveyed before.