Field of Science

Geological risks and human society

"Civilization exists by geological consent, subject to change without notice."
Will Durant (1885 - 1981) American writer, historian, and philosopher

Fig.1. Woodcut of the "terrible and great" water-flood in the year 1651 of the German river Rhine.

Earthquakes and volcanic eruptions are part of the activity of earth and not controllable or alarming as natural events; however as these events affect human infrastructure they became natural disasters.
Human population today tends to be concentrate
d in cities, in 1950 just 30% of the world's population lived in urban areas, today already it is 50% and until 2025 it will likely increase to 60%.

Unfortunately many urbanized areas are concentrated in regions with s
trong seismic or volcanic activity - cities and harbours developed along coasts where oceanic plates move under continental plates. Islands and regions with volcanic soils are very fertile and attract people. In contrast seismically stabile regions like Siberia or the interior of Australia are strongly weathered and the soils depleted of nutrients.
Considering the distribution of earthquakes and the density of population the most dangerous countries are located around the Pacific Ocean (the notorious ring of fire) like Indonesia, Japan, China, North to Central America and the Andes, also countries in the Near East and around the Mediterranean Sea are at risk.

Fig.2. Simplified map with earthquake events, volcanoes and larger cities, modified after U.S.G.S. 2005.

Fig.3. "...the resulting map gives each person living on earth the same amount of space while also preserving the geographical reference. This map allows to understand the earthquake intensity in relation to today’s population distribution, and thus gives an idea of where most people are of risk related to seismic activity.", Global Earthquake Intensity map after Benjamin Hennig 2011.

The increment and concentration of humans and infrastructure in narrow spaces increases the risk of and the impact from natural hazards like floods, earthquakes and volcanic eruptions, even small disasters can have great effects. Main problems are the to high grow rates, overcrowding population, no adequate infrastructures and development planes, limited space, mismanagement and corruption, all these factors increase the vulnerabilities of large cities and their inhabitants to local events.
Also modern technology and industry tends to be concentrate in single spots, however at the same time globalization tends to interconnect economies worldwide - a local catastrophe can so have worldwide economics percussions.
Living in highly technological cities also poses the danger that people loss contact and so awareness to natural hazards. In slightly modified or rural areas traces of past catastrophes can be observed, like landslide scars or deposits of rock fall or debris flows, in urbanized areas these traces tend to be smoothed or cancelled to build new infrastructures.
Defence or protection constructions tend also to smooth the temporal occurrence of natural hazards, most of these measures are build to prevent short term events of lower magnitude, producing the false impression that floods or mass wasting processes in general are extraordinary and rare events. People behind the protection w
all tend to be less vigilant or reduce private mitigation measures. When then an event is large enough to overcome the protection barriers, the results tend to be even more disastrous.

Even if natural disasters are not controllable, what is manageable is the response of single individuals and society to such a catastrophe, interestingly this response is strongly influenced by the former experience of catastrophes and the form of government in the afflicted region.

- The Netherlands, with large areas located on sea level, had to deal in historic times with floods and storms coming from the North Sea. In the last centuries with an ambitious project and kilometres of dams' additional large land areas lying below sea level were gained from the sea. The struggle against natural disasters is fought with technology and considered a task for the entire society.

- In the U.S. the answers to the inundation caused by hurricane Katrina in New Orleans were mixed between government actions and individual interests. Authorities reacted unprepared in a first moment and help was organized late, however there were strong efforts by local groups or individuals. When the government intervened, many homeowners refused to abandon their properties and tried to deal with the catastrophe independent.

- In strongly organized and centralized governments, like Cuba or China, ordered evacuations are followed mostly without opposition.

The wealth of a society plays also an important role in the results of a catastrophe. In the Indian city of Delhi the poorest people are concentrated at the city limits or in the areas of less interest for city planners, areas however in danger to become inundated, as happened in summer 2010 when the river Yamuna flooded the slums.

After many catastrophes follows the "blame game". Humans tend to connect an effect to a cause, during medieval times it was god or the devil, today it is mostly the behaviour of politics, economics or society. Often in the apparent rational blame a certain supernatural believe still persists. Many natural disasters are comprehended as a sort of revenge by misbehaviour of western civilization against nature, like regulation of rivers or overexploitation of natural resources.


CHESTER, D.K.; DEGG, M.; DUNCAN, A.M. & GUEST, J.E. (2001): The increasing exposure of cities to the effects of volcanic eruptions: a global survey. Environmental Hazards 2: 89-103

Online Resources:

SWAAF, K.F. de (20.03.2011): Von Ruhe bis Hysterie - So geht die Welt mit Katastrophen um. (Accessed 27.03.2011)

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