There are events that can't be predicted but could affect human civilisation drastically. They affect the world's climate and therefore human civilisation.

Space objects
One of these is large objects from space hitting the planet. These include comets and asteroids, or meteorites. The largest of these hit infrequently but can cause mass extinctions, of the type believed to have caused the end of the dinosaurs, identified as an object that hit the Yucatan coast of Mexico.

This is believed to have caused a long period of extreme climate conditions, including very high temperatures at first, followed by a long period of very low temperatures as dust and clouds in the atmosphere prevented solar radiation getting through to the surface.

It is estimated that it took a million years for plant cover to regain the quantity of the time before the object struck.

At the same time new species of animals evolved to fill the ecological niches left vacant by the extinct dinosaurs and other large animals.

An example within the historical period may be the events at the end of the Old Kingdom in the Egyptian civilisation. Reference

A chronicle of the time describes the Nile floods as being much reduced for many years with a resultant severe famine. This has been dated to about 2200 BCE. A crater in southern Iraq (revealed by Saddam Hussein's genocidal draining of the marshes) seems to be dated to about the same time. Reference Thus the reduction in the flow of the Nile lasting several decades may have been caused by a space object's impact on the African rainfall. The effects can be detected in ice cores in Greenland and Antarctica.

Super-Volcanoes
Some volcanic areas of the earth's surface have the power to affect world climate in an adverse way as much as a medium-sized space object.

The ice cores in Antarctica and Greenland show periods in the past when climate cooled suddenly, with signs of volcanic dust. Calderas can be seen in several areas. These indicate cubic kilometres of material have been expelled in sudden explosions.

The caldera at Toba in Indonesia is the site of a volcano which exploded about 40,000 years ago and may have almost wiped out the human species.

We may note that as recently as 1816 there was the "year without a Summer" caused by the explosion of the volcano Tambora in Indonesia in 1815. There was ice and snow in the summer months throughout the northern hemisphere, as far south as Pennsylvania in the United States, and harvests failed throughout this area.

One historical event can be seen in the island of Santorini or Thera between Crete and the mainland of Greece. Its explosion in 1650 or 1645 BCE (disputed date) is believed to have been the main cause of the disappearance of the Minoan civilisation and disruptions to all the human cultures around the Mediterranean.

Another historical event that has recently been identified is 1258 when there was no summer and a complete harvest failure. Many died in London of starvation. Although signs of a volcanic explosion many times greater than the most recent Krakatoa event have been detected in lake sediments and ice cores the actual site of the explosion has not yet been identified.

1258 Event

The effects of large volcanic events have been described in a useful book by David Keys - Catastrophe (1999). He traces the effects of an explosion, which he locates at Krakatoa (now between Java and Sumatra in Indonesia), in 536, which caused acute cooling throughout the planet, and major political changes in areas as far apart as Western Europe and China, and also the Americas. Keys argues that many of the modern states have their origin in the post catastrophe period (see Speculations).
He points out that in the US several sites, such as Yellowstone and Long Valley, California, have the potential to create huge climate changes and physical destruction affecting the whole planet.

One of the most active sites of a super-volcano is at Rabaul in New Guinea. This has been showing signs of activity during the 20th century. Others can be found near Naples Italy (Campi Flegrei) and in the Aleutian Islands. Slowly awakening are Yellowstone in the US and Long Lake in California, US.

It seems certain that at some time in the future many of these may explode, with serious effects on human civilisation. At present there is no means of estimating when.

Small scale event
The Icelandic volcano that erupted in April 2010 caused the shut down of jet aviation in Europe for a period, damaging the whole economy. A hypervolcano would be far more dangerous.

News
Pago volcano on New Britain, an island belonging to the state of Papua New Guinea is believed (October 2002) to be on the point of eruption. It is believed this may be a Caldera producing volcano. (It is more likely it will be on the scale of Pinatubo, which had mainly local effects, and a small global effect - several years when the average global temperature cooled a little, before resuming its rise). Reference
Earthquakes
26 December 2004 showed how destructive an earthquake can be when a tremor deep in the ocean at the boundary of the India-Australia plate and the Indonesian plate caused a Tsunami that affected the whole Indian Ocean area as far as East Africa. Probably some 300,000 people were killed directly and many others from the after effects.

There are also dangers of a similar Tsunami in the Caribbean area from the subduction zone north of Haiti, which could affect Florida and the Atlantic coast of the United States, and the eastern side of the Atlantic from west Africa to Europe. Is there a warning system?

The Haiti earthquake of January 2010 killed possibly 200,000 people, mainly from poor quality building.

Guardian survey.

David Keys - Catastrophe (1999)




Als die Sonne erlosch

Studies of volcanic events, earthquakes and Tsunamis

Bill McGuire - Apocalypse


Apocalypse: A Natural History of Global Disasters

Apocalypse: A Natural History of Global Disasters

Space objects might be detected by a space watch. If one is detected could it be deflected? It seems possible that a suitable space guard might be able to prevent such an object landing on the planet, if it is detected early enough. Discussion goes on in such agencies as the US space agency NASA about possible means of deflection.

Present day technology is probably not yet able to deal with one, but in the foreseeable future humans might possess suitable technology. Nevertheless, at present astronomical detection could not expect to detect every object and small ones of the type that exploded over Tunguska in 1908 would probably not be either detected or deflected. That object, if it had exploded over London, instead of over a nearly unpopulated Siberia, would have killed millions.

New Scientist article

Volcanoes
It seems very unlikely that any conceivable engineering could prevent a super-volcano explosion - or indeed, allow humans to prepare for an explosion and its subsequent effects.

An event of the type proposed for 563 CE could, if repeated today, result in the deaths of one to two thousand million people. This might well be accompanied by political disturbances, especially in the Third World. Keys suggests that the modern western type countries could survive such a period with their organised government systems, but would face severe food shortages and large numbers of refugees.

A Toba type event might again reduce humanity to a small group. Could such an event be foreseen?

Earthquakes
It seems unlikely that much warning can be given for earthquakes - they are always going to be unexpected, though clearly some countries are more vulnerable than others. Turkey, Iran and Japan are some of the most unstable.

What can be done is to design buildings so that they can resist even severe earthquakes. Almost all traditional buildings tend to collapse. Mud bricks as used in Iran nearly always collapse. In many countries building standards are ignored by more or less criminal building companies giving bribes to underpaid building inspectors.

Recent earthquakes in Turkey, Iran, Armenia have shown how sub-standard buildings can kill thousands. In Japan fewer people are killed by modern buildings.

All countries bordering the Pacific have a Tsunami watch system that detects undersea earthquakes and gives enough warning for coastal zones to be evacuated. On 26 December 2004 there was no system in place in the Indian Ocean, where earthquakes were considered less likely. The Indian Ocean is surrounded by less developed countries. A Tsunami watch could have saved thousands of lives in Sri Lanka and India merely by warning people to flee inland. The people killed in Somalia would have had many hours warning. A Tsunami watch is now being installed in the Indian Ocean.