In his latest book, Megadisasters: Predicting the Next Catastrophe, Florin Diacu looks at a variety of natural disasters, describing how scientists and mathematicians have struggled to understand and predict them over the centuries. In the excerpt below, Diacu tells the story of Tilly Smith, a young English girl whose vigilance saved around 100 lives in the catastrophic tsunami in 2004.
On the morning of 26 December 2004, Tilly Smith was with her parents and younger sister on the Mai Khao beach in Phuket. Ten years old, blond hair falling on her shoulders, Tilly looked jolly and fresh as she smiled in the sun. She had good reasons to be happy, thinking of the damp, cold England she had left behind. As mother and daughter went down to the water, Tilly noticed that the sea looked bubbly and frothy like on the top of a beer. This image triggered some recent memories in her mind. Two weeks earlier, during her geography class at Danes Hill School in Oxshott, Surrey, Tilly saw a movie about the Hawaii tsunami of 1946. She recognized the same warning signs: just minutes before the deadly wave hit, the water had begun to form bubbles and turn foamy, so very much as it did now.
‘A tsunami is coming!’ Tilly shouted. ‘We must run away!’
Her mother, Penny, had noticed that strange phenomenon too, but thought it was due to a bad day at sea, so she didn’t take Tilly seriously.
‘Mummy, we must get off the beach now!’ Tilly insisted.
Penny began to worry about her daughter, who started shouting madly at her, frustrated that her mother was blind to the danger. But in spite of her anxiety and irritation, Tilly didn’t give up. She had to convince her mother somehow. ‘If you’re not coming,’ she screamed, ‘I’m going to leave you here!’
Penny remembered Tilly’s recent geography class about tsunamis, so she gave in, and they both ran to Colin, Tilly’s father. After he heard the story, Colin alerted a lifeguard, who evacuated the tourists from the beach. It was a wise decision. Minutes later the killer wave showed up.
In September 2005, back in England, Tilly received the Thomas Gray Award of the Marine Society in recognition of her timely and decisive actions, which saved human lives. But she most cherished the inner satisfaction that she and her family, as well as the about 100 people who had been on the Mai Khao beach, were alive because she alone had recognized the danger.
Nothing happens without warning; it’s just that the signs are often obscure or opaque. Heart attacks, for instance, take many by surprise because they do not recognize the symptoms. The same problem occurs with most natural disasters. But the difficulty to acknowledge the message and act on the spot can be eliminated through training.
Most tsunamis give notice tens of minutes before they reach the shore. One or several of the following signs may be seen, heard, or felt:
. an earthquake occurs
. the sea recedes to a considerable distance
. the sea bubbles
. the water stings the skin
. the sea smells of rotten eggs or oil
. a flash of red light sparks on the sea near the horizon
. a boom is followed by a whistle, or by a jet-plane- or helicopter-like noise
Each phenomenon depends on circumstances, and their explanations vary. The sea’s recession compensates for the soon-to-arrive wave. The bubbling and the stinging of the skin, which resemble the effects of sparkling water, are consequences of the air or gases the wave pushes ahead of it. An earthquake or a volcano eruption may release chemical components with funny smells or lead to reactions that produce electrical discharges. Finally, the noises can be consequences of those reactions or may occur because of the friction between the large wave and the shallow seabed.
Some early warnings, which often occur before any of the physical signs are apparent, may come from nearby animals. The first documented animal reaction to a tsunami appears for the underwater earthquake of 1755, whose epicentre was some 350 kilometres southwest of Lisbon. The combined disaster killed between 60,000 and 100,000 people in Portugal, Spain, and North Africa, with the tsunami playing a lesser role in those deaths.
The earthquake struck on the morning of 1 November, causing wide fissures in Lisbon’s centre. Those who rushed to the docks for safety watched as the receding water revealed a seafloor littered by shipwrecks and cargo. More than an hour after the earthquake, a twenty-metre high tsunami, followed by two more waves, engulfed Lisbon’s harbour and downtown area. The animals are said to have run away from the shore long before the wave showed up.
The reason why animals feel the approach of tsunamis is yet unknown. Some scientists speculate that animals can detect certain earthquake waves, which propagate through the Earth’s crust.
Nevertheless, warning signs exist for tsunamis. But we need to learn how to read them. This is not always easy because we may see danger when there is none. Aesop’s tale about a shepherd boy who cried wolf to make fun of his fellow villagers shows how false alarms could do more harm than no warning at all. Nevertheless, Tilly Smith’s example proves that instruction and vigilance can save lives.