Living through an overturn
Let us consider a present day scenario.
The trigger could be the collapse of an ice sheet over the antarctic land mass. Once the ice starts to move it quickly accelerates as a layer of lubricating water and mud develops beneath it. It doesn't have to melt - just to flow out into the sea.
As the ice continues to flow, millions of tonnes per minute are moving. The mass of the polar region is no longer distributed evenly round the axis of rotation, and the earth starts to wobble on its axis. Just a little at first, but enough for sensitive instruments to pick up. As the ice flows the imbalance grows, and the antarctic crustal plate is now exerting more and more pressure on the plate opposite the ice flow.
An earthquake swarm develops along the plate boundary as one plate is pushed under the other. But much of the force is transmitted north through that plate and an earthquake swarm appears on its boundaries with the next, and the next.
The ice river launches minor tsunamis that radiate north from the flow, but each one raises the sea level a little. It doesn'tgo back down.
The time taken from the Ice sheet collapse to the next stage may be days, or months. But the relentless pressure of one continental plate on the next results in breakaway. very similar to the collapse of the ice sheets, but instead of being lubricated by water and mud, the continents are lubricated by a layer of molten rock.
At the point of breakaway changes happen fast, The whole crust of the earth starts to rotate over the core. For a moment the swarm of earthquakes die down - a few minutes at the most. Then a strange new type of earthquake is felt. A slow undulation of the ground, and in the middle of a continental plate, that may be all, accompanied by a vibration of the ground that seems to penetrate through everything, a deep rumble of continuous thunder.
People living in these areas would see the stars or sun appear to change direction, and in the space of an hour return towards the dawn. A rising sun might quickly set again, and a setting sun climb back into the sky. The following day the sun would rise in the west and set in the east. North would have become (almost) south and south (almost) north!
These would be the lucky people in areas of minimal disturbance. Rivers would flow back in their beds and form inland seas, or inland seas would drain down new valleys in vast floods.
The unlucky people would be those living on the margins of the continental plates, and regions where rift valleys form. Here, as the moving plates approach the equator - within the space of an hour - the plates stretch over the bulge of the equator, and rifts open through the crust. Volcanos spew ash and larva through the rifts. Natural gas escapes and ignites. The noise deafens and the ground shakes in violent earthquake.
As the crust moves over the bulge of the equator and towards the poles, the edges of continental plates are crushed together. In places within the hour, one crust is thrust over another plate into mountains miles high. The earth behaves like plastic and buckles and breaks. A mountain plateau is created in a chaotic jumble of crossing faults and fissures.
Again the heat generated melts rock and small volcanoes errupt through the fissures.
The ocean waters travel with the crust, but tsunamis propagate away from the violent upheavals on the plate margins. Sea water rushes in to fill a basin that sinks below sea level, or away from a sea bed now raised into dry land. Huge rafts of vegetation and dead animals and people are swept from coastal plains and are piled in drifts on shores hundreds of miles away. Hippopotomi and crocodiles from the rivers of africa are swept into the estuaries of Southern England, buried in drifts of gravel.
The luckiest people and animals are those that live close to the equator at the two points on each side of the earth around which the crust rotates. Here, although a continuous earthquake will still be felt, the forces are far less violent. Afterwards, the climate here may stay very much the same.
After an hour long earthquake the air is filled with dust and fumes of sulphur and volcanic ash. In the centre of the continetal plates, away from rifts, things settle down very quickly, but along the new mountain ridges, and in the zones of violent uplift, violent earthquakes continue at frequent intervals as the plates start to settle down.
Of the new volcanoes, some may die down in a few days, others months or years. Some will not start to die down for hundreds of years. Some newly created magma pools may not burst through to the surface for several hundrd years. An intense period of volcanic activity will decline slowly for thousands of years.
Climate change will also be dramatic and sudden. A temperate summer changes overnight to an arctic winter, a frost develops as the land cools that won't thaw until the next overturn. Coral reefs die in an arctic sea, and a new reef starts to form on a new tropical shore. Regions that remain in a similar climate zone retain their vast biological diversity - round the axis of rotation - but regions thrust into new zones see a rapid decline in species that cannot adapt to the new climate.
Civilisation has collapsed. Billions of people dead, but people will survive. In some regions some infrastructure will remain intact, but don't expect to be rescued.
Your first task is to work out where you have ended up on the new axis of rotation. Use the height of the midday sun in the sky to determine North and South, and your lattitude.
If the sun stays in the sky day and night you are in a polar summer - you have a couple of months to move towards the equator before winter sets in.
If the sky remains dark for 24 hours this might be thick volcanic dust, but if you see stars but no sun, you are in a polar region where winter will develop its chill in a few days. Find thick clothing immediately, and move towards the equator with maximum urgency.If you survive the next overturn it will be up to you to keep our civilisation going and help rebuild.
This information is copyright Peter Thomson 2005