But the top-ranked U.S. team was hurt in the third set when captain and three-time Olympian Lindsey Berg injured her left ankle.
Foluke Akinradewo added 15 points in the 27-25, 25-16, 25-19 victory for the Americans, who had clinched the top seed in their pool for Tuesday's quarterfinals.
Neriman Ozsoy scored 14 for Turkey, which was eliminated from the competition when defending Olympic champion Brazil swept Serbia (25-10, 25-22, 25-16) in the late match to survive.
Turkey, which came into the match 2-2, was fired up at the start and took a first-set 11-5 lead to the delight of a big turnout of Turkish fans at Earls Court. The U.S. came back with an 11-3 run and won it on Christa Harmotto's block.
The U.S. team breezed through the second set and took a 9-5 lead in the third, but then Berg limped off the court. The setter removed her shoe, and a trainer wrapped the ankle in ice.
Her team prevailed without her, winning the match on Akinradewo's kill. Berg limped to congratulate Turkey after the match.
Berg said afterward she would have the ankle examined further, but she didn't think the injury was serious.
"I'm OK," she said. "I felt something that wasn't worth pushing through."
The United States will play the 11th-ranked Dominican Republic in the quarterfinals, while No. 2 Brazil will face No. 9 Russia, No. 5 Japan plays No. 3 China and No. 4 Italy plays No. 15 South Korea.
The U.S. women have never won a gold medal in indoor volleyball. The team fell just short at the Beijing Games under coach Lang Ping, taking home the silver after falling in the final to Brazil.
Now playing under Hugh McCutcheon, who led the U.S. men to the gold in Beijing, the United States is among the favorites.
He said he was pleased with the effort of his team on Sunday.
"To me, one of the important characteristics of a great team is how you perform when there's nothing on the line," McCutcheon said.
Sunday was the final day of the preliminary round. Nataliya Goncharova scored 33 points and Russia clinched the top spot in its preliminary round pool with a five-set victory over Italy.
Ekaterina Gamova added 31 points in the 26-28, 25-19, 22-25, 25-16 15-11 victory for Russia. Simona Gioli had 21 points for the Italians.
Both teams were undefeated going into the match, and both had dropped just two sets. The teams had also earned spots in the quarterfinals, so the match decided pool finishing order.
Russia and Italy were joined by Japan and the Dominican Republic in advancing. Britain and Algeria were eliminated.
China defeated South Korea 3-2 with both teams earning a spot in the quarterfinals because of the five-set result.
A five-set match was the only way mathematically for both teams to advance to the quarterfinals. Had one team won all three points, the other team would have had to depend on results later in the day.
China won it 28-26, 22-25, 25-19, 22-25, 15-10, taking match point on Xu Yunli's kill.
Both coaches emphatically denied that they had purposely pushed the match to five sets to ensure a quarterfinal berth for both teams.
The result also meant that either Brazil or Turkey would be left out, depending on their late results. Serbia, which was winless in London, was already eliminated.
Japan defeated Britain 3-0 (25-19, 25-14, 25-12), eliminating the home team from the Olympic competition.
The 69th-ranked British women, who earned a spot in the Olympics as the hosts, surprised the field with a five-set victory over Algeria earlier in the preliminary round. Britain was not expected to win many sets, let alone a match.
The British, who had to raise money themselves to train and practiced in a small fire station gym, were given a sustained standing ovation from the crowd at Earls Court after Sunday's loss. One fan held up a hand-lettered poster that read "Thank You!"
"It has been unforgettable," British middle blocker Ciara Michel said. "We've been playing against the best teams in the world. It has been a phenomenal experience."
The Dominican Republic defeated Algeria 25-15, 25-16, 25-13 to advance. Algeria was winless in London, as was Serbia.
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