Quake debate

Woken by a deep rumbling, Nihat Altundag's family fled out into the street. "There are destroyed buildings around me, there are houses on fire," he reported.¹ "A building collapsed just 200 metres away from where I am now."

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 reach open spaces.

In rebel-held areas of SyriaA Middle Eastern country that was the site of much of the fighting during the Crusades., the situation was even more desperate. People dug with their hands 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 earthquake was very violent, measuring 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 hours later.

The Earth's crust is made up of rigid plates which move at about the speed that fingernails grow. Earthquakes occur when the plates rub against each other.

The forces involved are so strong 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 quakes. 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.