Quake debate

It was still dark when Nihat Altundag and his family were woken by a deep rumbling. With their house in the Turkish town of Pazarcik shaking, they fled out into the street. "Our house looks solid from the outside, but there are cracks inside," Altundag told a reporter.¹ "There are destroyed buildings around me, there are houses on fire... a building collapsed just 200 metres away from where I am now.

"Thank God, our friends are safe, but we heard there are people who can't get out of their homes and there are people we can't reach... We are waiting for the sun to rise so that we can see the scale of the earthquake. People are all outside, all in fear."

There were scenes like this across southern Turkey and northern Syria yesterday. In GaziantepA major city in south-central Turkey, with a population of 2 million. , close to the epicentreThe central focus of something. In an earthquake, the point on the Earth's surface directly above the focus. of the quake, people rushed to their cars and drove to the safety of open spaces. The city's Roman castle suffered heavy damage.

In rebel-held areas of SyriaA Middle Eastern country that was the site of much of the fighting during the Crusades., the situation was more desperate still. With a shortage of specialised equipment, people dug by hand to try to reach those trapped in the rubble.

By this morning, at least 3,381 people were confirmed dead in Turkey and 1,444 in Syria. Thousands more have been injured and an unknown number trapped in the rubble. The WHO has warned the number of dead could rise to about 20,000 in the coming days.

The region is no stranger to earthquakes. But few have been as violent as this one, which measured 7.8 on the Richter scaleA measure of the strength of earthquakes, developed by Charles Richter in 1935.. To make things worse, a second earthquake measuring 7.5 hit the area 11 hours later.

According to the theory of plate tectonics, the Earth's crust is made up of a dozen rigid plates which move at about the speed that fingernails grow. Earthquakes occur when the fault lines between them come under too much pressure as the plates rub against each other.

The forces involved are so powerful that some scientists believe they have increased the speed at which the Earth spins. In June its shortest day ever was recorded, with 1.59 millisecondsOne thousandth of a second. shaved off its usual 24-hour rotation.

One expert, Professor Bill McGuire, argues that climate change is making the world more vulnerableat risk of being harmed to earthquakes. He imagines the Earth as "a slumbering giant that tosses and turns periodically in response to various pokes and prods".

When the great weight of ice disappeared at the end of the last Ice AgeA long period of time in which global temperatures are extremely cold., he writes, "the crust popped back up like a coiled spring released, at the same time tearing open major faults and triggering great earthquakes".

Now, he fears, global warming could cause similar "geological mayhem" by causing the ice sheets of the Arctic and Antarctic to melt.

Yes: Bill McGuire's theory is persuasive. Glaciers have been melting at a staggering rate, and without that weight of ice on the Earth's crust tectonic plates can move more easily, causing more quakes.

No: McGuire may be correct, but the changes caused by the end of the last Ice Age took tens of thousands of years. It is too soon for global warming to have had a similar effect in our own era.

Or... It is hard to know. Fault lines have been causing earthquakes throughout history, but there are so many different factors involved that we cannot say for sure whether climate change is one of them.