Matt Cain (7-8) retired 15 of the first 16 batters he faced. He struck out five and walked one in seven innings, allowing only an RBI single by Nate McLouth in the sixth before Hardy's homer carried over left fielder Jeff Francoeur and into the first row.
"I thought it was a pop-up that Francoeur would have caught easily. It just kept going," Cain said.
Troy Patton (2-0) tossed one scoreless inning of relief to help Baltimore to its fourth win in five games.
Norris gave up six hits, struck out two and walked two in five innings. He had won his first two starts since the Orioles acquired the right-hander from Houston on July 31.
Norris wanted to stay in the game but was hit for in the fifth. He said he goes into every start "programmed" to throw 120 pitches, though Showalter said he called Norris out on his math, saying he averages about 98 a game.
Even still, Norris enjoyed watching the offensive outburst in the late innings.
"It's a lot of fun. It's something I'm definitely not really used to" coming from the Astros, he said. "Screaming in the clubhouse, I think I scared one of the trainers off the table."
The finale between the black-and-orange and the orange-and-black turned out to be a one-sided affair.
Cain, long accustomed to receiving little run support, baffled Baltimore's batters most of the afternoon. He sent down the first eight he faced before Norris' comebacker bounced off his glove, knocked him down and trickled around for an infield single.
The Orioles couldn't crack Cain again until Brian Roberts tripled leading off the sixth. After pinch-hitter Henry Urrutia struck out, McLouth singled to slice San Francisco's lead to 2-1.
A day after hitting his majors-leading 42nd home run, Chris Davis doubled off the 399-foot marker in center leading off the seventh. Two batters later, Hardy homered to left to put the Orioles ahead.
Jones sent a changeup from starter-turned-reliever Barry Zito over the wall in left in the ninth to put the Orioles up 10-2. That sent most of the announced sellout crowd of 41,622 headed for the exits.
San Francisco's stagnant offense never put up a fight. The Orioles retired 17 of the final 19 batters for the Giants.
Buster Posey, the reigning NL MVP and batting champion, is hitless in his last four games and in a 2-for-19 skid. World Series MVP Pablo Sandoval, who turned 27 on Sunday, snapped a 0-for-20 skid when he singled in the sixth and also walked twice.
"We scored two runs early and then it's like we sit around and wait," said Giants shortstop Brandon Crawford, who was 0 for 3 with a walk. "We just kind of sit on the two-run lead and think that's all we need. A lot of times with our pitchers it is, but we have to pile on when we can."
Orioles INF Wilson Betemit (right knee) will begin a rehab assignment at Class-A Frederick on Monday, while OF Lew Ford (sports hernia) will report to Double-A Bowie on Tuesday. ... Giants CF Angel Pagan is progressing well in Arizona from left hamstring surgery and could be ready to make a rehab start soon, manager Bruce Bochy said. The Giants hope Pagan can return around Sept. 1. ... The Orioles begin a three-game series at Arizona on Monday. The Giants are traveling to Washington on Monday to open a three-game set against the Nationals on Tuesday.