Researchers finish Crater Lake map
August 04, 2000
By PAUL FATTIG
CRATER LAKE — Ancient landslides and lava flows never before seen by humans have been revealed at the bottom of the nation’s deepest lake.
The revelations came as scientists from the U.S. Geological Survey and the University of New Hampshire mapped the lake bottom with the latest deep-sea technology in a unique project at Crater Lake National Park.
But you don’t have access to sophisticated underwater mapping gadgets to glimpse the submerged caldera: the researchers have been posting online computer images of their work at http://tahoe.usgs.gov/craterlake/
“It went smooth as silk,” said Jim Gardner, a marine geologist who is chief of Pacific sea-floor mapping for the USGS in Menlo Park, Calif.
A military helicopter with an Army reserve crew from Fort Lewis, Wash., carefully lifted the 11,200-pound research vessel from the lake to the rim Thursday morning, reversing its mission of July 28.
The lake is the remnant of a 12,000-foot volcano that erupted 7,700 years ago.
While there were no apparent surprises found at the lake bottom, project scientists won’t know for sure what they’ve got until other scientists pore over the data collected, Gardner said.
“Our job was to map the bottom,” he explained. “Now it’s up to other scientists to look for surprises.”
More images will be available on the Internet in the coming weeks, he said, noting that the USGS will also produce a CD-Rom of the lake bottom.
“We’ll give that away to anyone who wants it once it’s completed,” he said.
The nearly $200,000 mapping project was the first to map the scenic lake since 1959. However, the mapping technique used more than 40 years ago was crude compared to modern sonar systems, said Mac Brock, the park’s natural resource manager.
In addition to the maps, scientists are creating three-dimensional images of the lake floor, he said.
“Eventually we will have an interactive display in our visitor center so that anyone can take a ‘tour’ of the lake bottom,” Brock said.
Although the scientists of 1959 mapped with acoustics, their equipment lacked the multi-beam capability of today’s equipment. Gardner and his associates relied on high- resolution multi-beam echo-sounder technology, which sends out pulses of sound two to three times a second.
As a result, instead of the roughly 6,000 sound beams used for mapping in 1959, more than 50 million beams were pinged to the bottom this past week. Each will be accurate to within 50 centimeters, Gardner said.
The focal point was the geothermal vents on the lake floor, which is 1,932 feet below the surface at its deepest point.
In 1988, scientists in a tiny submarine surveyed about 2 percent of the lake floor. During that survey, they discovered hydrothermal vents with bacterial mats and tiny mites living around them.
This week’s research was done by a craft containing $3 million in state-of-the-art equipment and owned by C&C Technologies Inc., of Lafayette, La. The firm specializes in underwater mapping.
More than half of the $200,000 price tag was paid for out of a settlement with American Eurocopter of Grand Prairie, Texas. After a helicopter owned by the firm crashed into the lake in September 1995, the firm paid the Park Service $122,500.
Federal law requires owners of crashed aircraft to remove wreckage from crash sites in national parks.
“But the helicopter disintegrated when it crashed on the surface of lake,” explained park spokesman John Miele. “Chances of recovering it would have been slim to nil.
“An operation to recover anything from the bottom of the lake would have been very costly and risky.”
The pilot and a passenger died in the crash. Their bodies were never recovered. It’s unknown whether the underwater mappers have found the remains of the craft, Miele said.
“Everything looks like rock at this point,” he said. “They have to analyze the density of the material to determine whether they have found the remains of any of the wreck. That’s going to take a while.”