For the first time, 3-D images made with high-resolution sonar clearly reveal the stern and steam-powered paddle wheels of a historic shipwreck, the USS Hatteras, that has been on the bottom of the Gulf of Mexico for 150 years.

"It's like an intact time capsule from the Civil War," said Jim Delgado, maritime heritage director for the federal Marine Sanctuaries program, who directed the use of the new sonar technology to map the wreck last September. He released the images for Friday's anniversary of the sinking.

"The Hatteras was the only Union ship to sink in Galveston Bay during the Civil War," said Delgado, noting the ship was brought down in 1863 by the famed Confederate warship CSS Alabama.

Delgado will lecture about the 3-D images and the sinking at 6 p.m. on Friday in the auditorium at 1 Moody Plaza in Galveston.

Photos: See more images of the USS Hatteras

The discussion is part of a two-day recognition of the Battle of Galveston, during which Confederates regained control of the bay from a Union blockade. By the end of the war, Galveston was the only port still held by the Confederacy.

Half of wreck intact

The Hatteras site is one of the few listed on the National Register of Historic Places. It's in a location protected from heavy wave action.

The Hatteras was in the vanguard of the transition from wooden sailing ships to steam-powered ones. The 210-foot iron vessel had both steam-powered paddle wheels and masts for auxiliary sails in case it ran out of fuel or needed assistance from the wind.

Surprisingly, Delgado said, at least half of Hatteras' wreckage is still intact about 20 miles off the island in 59 feet of water, partially buried by 3 feet of sand.

The murky, silt-filled waters have concealed the wreckage until these new underwater images were painstakingly made by divers using the sonar equipment. The images were then fed into a computer.

Delgado said the images confirmed the stories of the ship's demise.

"What we saw were a number of fatal blows," he said. "Essentially the port side was shot full of holes. Then the ship took on water and flooded fast. Shots went through the engine room, rupturing the steam lines and filling the room full of blistering steam." The engine room is where two men who stoked the coal fires died. They were the only crew members to go down with the ship.

Delgado believes the wreckage shows the bravery of the crew. The Hatteras had been built to ferry passengers, but shortly after being launched it was purchased by the Union and transformed into a fighting ship.

End came quickly

In two years of service, it attacked merchant ships trying to run the Union blockade. The Hatteras is credited with bringing down seven such vessels off the Florida coast.

But the Hatteras, while equipped with 32-pound cannons, proved no match for the Alabama, a ship that had been designed and built for war. The faster, more powerful Alabama sank the Hatteras in only 13 minutes, Delgado said.