The skyscrapers of Manhattan symbolise political and financial power and are an open provocation to photography. Has there ever been a city that more desired to be pictured than New York? Designed to awe the eyes, the financial district skyline received thousands of glowing reviews daily from captured photos and dispatched postcards.

For this reason, it is cruelly appropriate that the attack on America is essentially a photo story. Reporters and columnists terribly resent the platitude about a picture being worth a thousand words, but for at least the first 24 hours - with few facts and no culprits - prose ran a hopeless second in the telling of this story.

Representing, through its movie industry and multi-channel television, the most visual culture there has ever been, America also has a film-star obsession with its own looks. Even its military headquarters - the Pentagon - wanted to be an architectural wonder.

So it is right that, whatever else happens, the things we will never, ever forget are the photographs. The picture-book nation has now produced an album of terrible negatives. Some of the images - the jet heading directly for the tower; the World Trade Centre engulfed in flames; the people diving to certain deaths from the buildings - will become as horribly iconic for future generations as the young girl fleeing screaming from the napalm in Vietnam, or the red cloudburst of President Kennedy's head in Dallas.

But looking at what was shot as America snapped, what strikes me first is that the most vividly appalling images are all, in a strange way, palimpsests: reflecting other images from the nation's visual memory, whether factual or fantastic.

Take the pictures of the towers smouldering and then crumbling. What is the scene that citizens have most feared seeing for the past five decades? It is the sight of a great city enveloped in a cloud of dust and rubble. We expected it to be the nuclear mushroom cloud - the shape that has haunted our imaginations since Hiroshima and Nagasaki. It is an image we have already seen in the quasi-reality of Hollywood movies, which have regularly explored the deep fear that someone might, one day, take up the challenge to potency thrown out by America's tumescent skylines. In Independence Day, Manhattan is flattened by extraterrestrials. In Spielberg's AI the twin towers are brought low, though by flood rather than fire.

In the news pictures, Americans see the image that they for so long feared the Soviet Union might create - the World Trade Centre in a mushroom cloud of dust - produced long after the Cold War by a nameless nemesis. Even the thick dust that stuck to the people running from the buildings resembled the radioactive ash so fixed in imagination and cinema during the US-Soviet Union stand-off. Indeed, these scenes are so close to our imaginings of nuclear war that it is almost as if some photographic Nostradamus has proved to be only very slightly wrong in his predictions.

There is another pictorial echo in the shots of the twin towers imploding. Because the metal communications wand on top of one of the buildings looked so like those on top of space rockets - and because a rocket is launched from vast clouds of fire and smoke - the fall of the towers recalled film of an Apollo rocket launch played in reverse. This visual mimicking is again painfully fitting, because the moon-shot project was, in common with the New York skyscrapers, a symbolic declaration of American size and reach.

THE image that chronologically preceded the pseudo-nuclear explosion - of one of the jets heading directly for the World Trade Centre - looks like some sick satirical twist on the picture that still dominates airline advertising: the liveried airliner, proud in the clouds above a city. It also eerily reproduces a scene that has filled minds and movies since the World War II: terror from the skies, the fear that one of our most celebrated inventions might be turned against us.

Aerial attack from spacecraft or booby-trapped plane is a standard plot of the disaster movie, and the narrative device of a terrorist bomb from above also powers books by two of America's best-selling writers: The Sum of All Fears by Tom Clancy and Black Sunday by Thomas Harris.

Another panel fixed on the collective retina this week - people diving from the towers, in effect preferring one death to another. This also had a terrible but apt visual antecedent. In 1929, stockbrokers threw themselves from banking towers because they had no desire to stay alive, a moment captured in iconic pictures of the Depression. In 2001, financiers made the same Wall Street fall because it was their one forlorn chance of escaping death. The suicide of bankers and the homicide of bankers are joined in a visual time-loop.

These are the photographs that the history books will hold. But, far away from New York and Washington, the day produced another picture that will be less noticed but was probably unique in political history. As George W. Bush read a story to Florida schoolchildren, he was interrupted by his chief of staff, Andrew Card, who whispered the news from New York.

Politicians almost always find out about their crises in private. They have time to compose the face they will later show on television. One distant day, their memoirs will reveal how they were told. But it fell to Bush to take in public the worst news an American leader has ever received in peace-time. His startled and uncomprehending expression should perhaps be shown as a warning to all who seek a life in public office.

The events of that terrorist super-Tuesday give a nearly unbearable piquancy to old pictures of New York. The skyline that loved to be in photographs now exists only in them.

- GUARDIAN