IN golf, as in nature, earthquakes happen when continents collide.
This week, Chicago will be rocked to its firm sporting foundations by a Ryder Cup battle of seismic potential between the United States and Europe.
Twice before on American soil this event has gone off the Richter Scale -- vast fissures appearing between the two sides at Kiawah Island in 1991 and Brookline eight years later.
Patriotic fervour, stirred by General 'Storming' Norman Schwarzkopf's victory in the first Gulf War, and prickly mistrust between two teams not well enough acquainted to know better, cranked up the animosity at Kiawah.
There were even pre-dawn calls to European players from a Charleston radio station, and others joined in when room telephone numbers were given out on air.
At Brookline, a noisy Boston crowd was stirred to rabid excitement as the home team embarked on a stunning Sunday comeback.
Then the match erupted into huge controversy when the US players and their partners infamously stampeded on to the 17th green to celebrate a monster birdie putt by Justin Leonard.
Leonard had come back from the dead against Jose Maria Olazabal to clinch Ryder Cup victory with that putt... or so his team-mates thought. In fact, the Spaniard had a birdie putt of his own to send the game up 18.
When calm eventually was restored, Olazabal missed; the American celebrations resumed and the Europeans seethed.
Well, not all Europeans.
Padraig Harrington played the first of his six successive Ryder Cups at Brookline and still believes, "in terms of pure excitement on a golf course, that was special... and I've won three Majors."
Unlike Colin Mongomerie -- who was the target of such vicious verbal abuse that Sunday at Brookline that his father left the course in disgust and his opponent, Payne Stewart, had some spectators ejected -- Harrington was well received by the Boston Irish.
While Monty could be disturbed by a butterfly breaking wind on the next fairway, Harrington, on his Ryder Cup debut, put his special powers of concentration to good use at Brookline.
"When there's needle, it's exciting," says Harrington. "Okay, I don't think there was any needle at Celtic Manor two years ago and that was exciting. So what you really need is for the Ryder Cup to be very close. Then it's exciting."
And Medinah is going to be very, very close, he expects.
"It really is beginning to look like that. The US (players) were very strong in the summer but now it all seems to have evened itself going into the match."
With just under 10 million people living in its greater metropolitan area, Chicago is the third largest city in the US behind New York and Los Angeles, with strong ethnic links to European countries like Ireland, Poland and Germany.
The passion for sport there is powerful, whether it's the Bears or the White Sox, the Cubs or the Bulls, whose golf-mad former talisman Michael Jordan has been called up by US skipper Davis Love III to tour the fairways at Medinah helping focus support for the home team.
Chicago was beaten by Rio in its bid to host the 2016 Olympics and also has been frustrated in its efforts to bring American football's Superbowl to town, so city residents have heartily embraced this Ryder Cup.
Given that Harrington enjoyed Brookline and believed that Ben Crenshaw's side paid Europe a compliment with that celebratory stampede in 1999, he'd have relished the opportunity to perform in front of a vociferous Chicago crowd at the weekend.
"It started out with a good atmosphere that Sunday in Boston. I had a lot of Irish-Americans following me and everyone was having a great day," he recalls. "Then David Duval won 5&4 in front of us and from that moment on there was a big surge in the numbers following our game.
"They started shouting at Mark O'Meara that he needed to win. They were supporting him, but it was pressure as well. I particularly remember the noise as we walked after our shots on the par-three 16th. It was like standing beside the speakers in a disco."
Harrington's caddie that day, Dave McNeilly, adds: "You could see more and more of the American team arriving at our match, so it really looked as if it was coming down to us.
"I've never been as nervous in my life. Padraig had about a five-and-a-half-foot putt for a half on a par-five and the crowd were so vociferous my mind was just shutting down. I couldn't handle watching it, never mind standing over that putt or holing it.
"As we were leaving each green for the next tee, it felt like walking into the ring for a boxing title fight. You were passing through this avenue of people and they were literally screaming into your face.
"You just kept your head down, tried to keep focused on the next hole, tried to keep your mind clear for thought," explains Ulsterman McNeilly, who was amazed by Harrington's ability to block it all out as he trundled on to victory.
"I'll never forget, Padraig hit a three-wood down 17 and this will tell you what a strong mind he has: he walked 70 yards up to the green to see how hard the surface was and then walked back to play his second shot.
"He was booed all the way because they thought he was trying to slow-play Mark. He didn't even notice, he was so much in his own world at that moment."
Irish golf will be represented by Rory McIlroy and Graeme McDowell at Medinah, and Harrington expects both to play a prominent and powerful role.
World No 1 McIlroy has grown from a wide-eyed though richly talented rookie at Celtic Manor into a team leader in Chicago, while McDowell truly is a Rottweiler when it comes to match play.
It didn't surprise Harrington to hear Jim Furyk describe McIlroy as "a marked man" at Medinah, though he disagrees with Paul Azinger's assertion that the US merely have to "beat Rory to win the Ryder Cup".
"All they're basically doing is substituting Rory for Tiger," he says. "We Europeans would always put a bullseye on Tiger's back, and the Americans are doing the same to Rory. For sure, if they manage to beat Rory, it'll make it harder for Europe to win, but it doesn't mean they will win the Ryder Cup.
"It was great to see Rory get himself into contention over last weekend at the Tour Championship. There's nothing like being able to do that when you're not firing on all cylinders, and everything he's done since the US PGA has been building him up nicely for Chicago.
"Rory and Graeme are guaranteed to start the first morning in the foursomes. You could put your house on that, while you'd be surprised if they were split up in the afternoon fourballs. Working out the partnerships in foursomes and fourballs and trying to get everyone a game on the first day is a big deal," he adds. "It's much easier to pick your pairings for the second day."
The ability of Peter Hanson at foursomes is likely to earn him a place in that opening session on Friday morning. Meanwhile, rookie Nicolas Colsaerts is a cert for that afternoon's fourballs, Harrington believes.
Sunday's singles line-up is probably most critical of all, he says. McIlroy and Lee Westwood are obvious candidates to lead out the team, though Ian Poulter will also figure very close to the top of the order.
"Like Monty, Poulter could never play at eight, nine or 10," Harrington explains. "He wants to be getting a big win early on and dominating. I'm not saying he wouldn't do the job down the order, but the last thing you want is him out there playing when the match looks like it could be over and he's possibly getting distracted by the leaderboard."
By contrast, McDowell is the perfect tail-gunner, as he proved with his match-clinching victory over Hunter Mahan at Celtic Manor.
"He's somebody in my own mindset. He wants the toughest possible pressure-filled match -- to play an opponent who's under pressure and wants to grind it out," says Harrington.
"Graeme doesn't want to get caught by some guy in the middle of the pack who gets on a run and shoots seven or eight-under. He wants to get the guy who has watched all the leaders go out, who knows his game is pivotal and is under a lot of stress. It's going to be a tough grind the whole day and it's going to come to the last couple of holes."
Harrington dismisses concerns about Westwood's poor form and last-place finish in Atlanta last Sunday.
"Don't you worry about that," he says emphatically. "Lee's too long in the tooth to have any such concerns. I've no fears for him at Medinah, none whatsoever."