Scientists study mystery mounds under Hood Canal
SEATTLE (AP) - Washington scientists guessed that mysterious mounds hundreds of feet below the surface of Hood Canal were deposited by Ice Age glaciers or built up by natural gas seeps or geothermal vents.
After taking a closer look with a remote control camera they have another theory: Underwater landslides.
There are two dome-shaped mounds, each more than 100 feet high and more than 1,000 feet wide, on the bottom at the south end of the canal near Lilliwaup.
Scientists with the Department of Natural Resources and Fish and Wildlife Department used a submersible vehicle in 2008 to take a closer look. They decided the mounds were created by underwater landslides of sediments that had built up at the mouths of two small rivers.
The study has been discussed at conferences, but budget cuts were one reason the report wasn't published until November by the Division of Geology and Earth Resources. The department also reported the study in its blog, Ear to the Ground.
Department scientists first noticed the mounds in sonar maps made by the University of Washington in the canal, which is not manmade. It's a 68-mile fjord on the west of Puget Sound. Hood Canal is a popular area for vacation homes. It's also the location for the Navy's submarine base at Bangor, home to the West Coast Trident fleet.
"We were left scratching our heads," said Michael Polenz, a Department of Natural Resources geologist involved in mapping the canal for possible hazards.
They were able to rule out glacial deposits, which are usually ridge-shaped. And there was no sign of seeping methane or discharging geothermal vents.
The location was the best clue to the origin of the mound. One is off the mouth of the Duwatto River and the other off the mouth of the Little Duwatto River.
They are the only rivers on the Hood Canal without deltas, said Tim Walsh, chief hazards geologist with the DNR.
It's assumed the unstable deltas slid to the bottom of Hood Canal, perhaps in an earthquake about 1,000 year ago. Similar underwater landslides today could cause a tsunami on the canal, depending on the speed of the landslide.
"We have a lot more questions than answers," Walsh said Friday.
The underwater camera also gave the Fish and Wildlife Department a look at rockfish and other marine life.
"They found evidence of rockfish in places they hadn't expected them to be," Walsh said.
After taking a closer look with a remote control camera they have another theory: Underwater landslides.
There are two dome-shaped mounds, each more than 100 feet high and more than 1,000 feet wide, on the bottom at the south end of the canal near Lilliwaup.
Scientists with the Department of Natural Resources and Fish and Wildlife Department used a submersible vehicle in 2008 to take a closer look. They decided the mounds were created by underwater landslides of sediments that had built up at the mouths of two small rivers.
The study has been discussed at conferences, but budget cuts were one reason the report wasn't published until November by the Division of Geology and Earth Resources. The department also reported the study in its blog, Ear to the Ground.
Department scientists first noticed the mounds in sonar maps made by the University of Washington in the canal, which is not manmade. It's a 68-mile fjord on the west of Puget Sound. Hood Canal is a popular area for vacation homes. It's also the location for the Navy's submarine base at Bangor, home to the West Coast Trident fleet.
"We were left scratching our heads," said Michael Polenz, a Department of Natural Resources geologist involved in mapping the canal for possible hazards.
They were able to rule out glacial deposits, which are usually ridge-shaped. And there was no sign of seeping methane or discharging geothermal vents.
The location was the best clue to the origin of the mound. One is off the mouth of the Duwatto River and the other off the mouth of the Little Duwatto River.
They are the only rivers on the Hood Canal without deltas, said Tim Walsh, chief hazards geologist with the DNR.
It's assumed the unstable deltas slid to the bottom of Hood Canal, perhaps in an earthquake about 1,000 year ago. Similar underwater landslides today could cause a tsunami on the canal, depending on the speed of the landslide.
"We have a lot more questions than answers," Walsh said Friday.
The underwater camera also gave the Fish and Wildlife Department a look at rockfish and other marine life.
"They found evidence of rockfish in places they hadn't expected them to be," Walsh said.
Actually John Locke turned the wheel and The Island moved.
:)
An ode to the best TV series ever.
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At first I thought they were going to be talking about the Mima mounds in Thurston County.
It's Dewatto, not Duwatto.
I think the big holes in the Hood Canal are more interesting. If you get up above Lake Cushman on a nice clear day you can see the holes from up there. Have used my depth sounder on them when I've been out there fishing and some of the holes are over 1000 feet deep. You can catch a lot of cod if you fish the lips of the holes during high tides.
I wonder where the rock fish were found that they didn't expect to see?
Lost submarines from Bangor.
It's Atlantis, Its Atlantis........oh wait.......it just a bump.......darn it!
 @Susabelle Got earthquake insurance?
 @Common-Tater  @Susabelle Yep.
 @Susabelle You beat me to it!
Must be a slow day in some government office somewhere.
well the state could hire a companie to do a geo sizemic survay to see what is under those mounds an what is under the floor of hood cannal maybe the state would find oil and gas. and then gennerate some real revenue.
Duwatto??? try Dewatto
Duwatto may be a closer spelling to the Twana name for the rivers. I wonder what type of Tsunami would be generated if the Hamma Hamma river delta slid off into deep water?
 @None Depending on how fast and how big the slide was, it could be a couple hundred feet tall.
This comment has been deleted
 @A.V.  @None No, as usual the white men just weren't paying attention...
 @Dumbfounded883 For sure.Â
Directly north of this in short distance is the Olympic Mountains. Go figure that one out. There is geothermal energy in this area, as yet not capitalized on.