It took 160 years to build the city of Christchurch. It took an earthquake 24 seconds to rip the heart out of it.
Some buildings were reduced to piles of masonry and concrete and twisted metal almost instantaneously. Hundreds of others remained standing but damaged beyond the point of salvation. A century and a half of human endeavour was wasted in less than half a minute.
But nothing of this compares with the human tragedy. In that half a minute, 185 people died or were mortally wounded. Others were maimed, injured, trapped and broken in spirit.
We measure our lives in the numbers of hours, days and years. Some numerical sequences assume a seemingly intolerable burden of loss and tragedy. Think of 1914-1918. Think of 9/11. Christchurch people cannot but think of 12:51 22/2/11.
That hour on that day will forever be a dividing point for Cantabrians. If you were there, the progress of your life will be measured in part by what happened before that time and what came after it.
If you were there, you will instantly know something of the common tragedy shared by all.
The experience is indescribable, but let's try. There is the noise; louder and more frightening than any thunder. There are pure, visceral forces of nature - movements of the elements that no muscle in the body can possibly counteract. There is the choking dust. And there is the fear; always the fear, to be rekindled anew a little with each of the thousands of aftershocks. You cannot fight any of it. All you can do is endure, and for some, at the worst time, to hope to survive.
But in the midst of that worst time, there was also heroism and self-sacrifice. Stories are told of people who died to save others. For many of the victims - those who were trapped, who had to confront what one of them has called the 'dark place' - there were the rescuers who stayed behind to help at a time when many people chose to flee. Ordinary people doing extraordinary things.
There is now a new vocabulary. Liquefaction. Post-traumatic stress. Survivor guilt. GeoNet. Things that were remote, technical or theoretical before - up to and including the seemingly random movements of tectonic plates - suddenly become immediate and personal.
And then there is human contact. The smile, the touch, the words that are given and received as the most precious gift. Eyes lock. Friends embrace. Loved ones kiss. Strength comes from knowing that you are not alone.
A disaster leaves people helpless and out of control. In its aftermath, the best thing to do is little by little, step by step, take control back.
It happens in a grim sequence: cover the dead, look after the injured, evacuate from danger, find loved ones, seek security and home and shelter, secure water and food and provisions, pick up a broom or a shovel, clean up the things that have fallen, ensure warmth and light and cater for bodily needs.
Try to plan for the future. Tomorrow will dawn and there will be a new normal.
Ric Stevens is the Deputy Editor of The Press in Christchurch.