Differential Impacts & Tectonic Hazard Patterns (Edexcel A Level Geography): Revision Note

Tectonic Hazard Trends Since 1960

Global disaster trends

• The number of recorded disasters has increased significantly since 1960

• There are a number of reasons for this including:

  • Increased population - the world population has grown from 3 billion to over 8 billion since 1960

    • This means more people are likely to be impacted by any hazard event

    • Increased population density in urban and coastal areas increases the vulnerable population

  • Increased monitoring and reporting means more hazard events are recorded

• Most of the increase has been the result of floods and extreme weather

Tectonic disaster trends 

• The number of tectonic disasters has fluctuated since 1960 but has generally remained steady

• The slight increase in a number of earthquake disasters does not mean there have been more earthquakes or higher magnitude earthquakes. It results from:

  • Greater urbanisation leads to higher population densities and increased building density

  • Population growth means more people are living in earthquake-prone regions

Number of deaths

• The number of deaths resulting from all hazards has decreased since 1960

• This is the result of:

  • Improved building construction, design and materials 

  • Increased monitoring 

  • Greater preparation and planning - hazard mapping, land use zoning, evacuation planning

  • Education - earthquake drills

  • Improved warning systems 

  • Increased development

• The number of deaths from tectonic hazards fluctuates depending on a range of factors including:

  • Magnitude

  • Level of development

  • Location

                                                  1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010  2020

• The impact of a mega-disaster such as the Indian Ocean earthquake and tsunami may skew the overall trend because it leads to so many deaths

• Volcanic eruptions are less frequent than earthquakes and deaths from eruptions are now rare due to improved monitoring, exclusion zones and evacuation plans

Numbers affected

• ‘Numbers affected’ is another impact metric, alongside deaths and economic cost

• It counts people who survive but are injured, made homeless, displaced or left needing aid

• It is usually far larger than the death toll, capturing the full human scale of a disaster

• Numbers affected are often highest in emerging and developing countries, where many people lose homes and livelihoods even when deaths are kept low

Insert image: People affected by earthquakes and volcanic activity worldwide
Image caption: People affected by earthquakes and volcanic activity worldwide, 1960–2023. Source: EM-DAT, CRED (via Our World in Data).

• The graph shows how many people were affected by tectonic hazards (earthquakes and volcanic activity) each year

• Most years fall between about 1 and 5 million, but occasional spikes reach tens of millions

• The spikes occur when a large earthquake strikes a densely populated area:

  • 2008 — the Sichuan earthquake in China affected around 46 million people

  • 2023 — the Türkiye–Syria earthquakes affected tens of millions

• Unlike deaths, which have fallen since 1960, numbers affected have not fallen — population growth and urbanisation put more people in earthquake-prone regions

Economic cost trends 

• The economic cost of disasters has increased since 1960

  • As countries develop the cost of repairing infrastructure and rebuilding increases 

    • Increased wealth means people have more possessions and property to be damaged and destroyed

    • Infrastructure is more sophisticated and expensive to replace, for example, electric grids 

  • As more people are affected the cost increases

• The economic impact of disasters is affected by whether the country is developing (LIC) or developed (HIC)

  • The economic cost in US$ tends to be higher in developed countries

  • The impact on the GDP tends to be much greater in developing and emerging countries

Comparison of Costs LIC Vs HIC

Accuracy and reliability of data

• The trends associated with all disasters are complex

• They are affected by a wide range of factors

• When disasters occur the data collected may not be accurate due to:

  • The focus when a disaster strikes and in the weeks that follow is on search, rescue and recovery

  • In remote rural areas it may be difficult to collect data

Skills — interrogating the data (skill 6)

• The trends on this page come from large secondary datasets you can explore yourself:

  • EM-DAT — the Emergency Events Database, run by CRED (the Centre for Research on the Epidemiology of Disasters): frequency, deaths, numbers affected and economic cost by disaster type and country

  • USGS — the United States Geological Survey: global earthquake catalogue, magnitudes and the “Did You Feel It?” intensity data

  • UN GAR — the United Nations Global Assessment Report on Disaster Risk Reduction: modelled risk and exposure datasets

  • These datasets can be used to plot change over time and to test whether rising disaster counts reflect more hazards or better recording

Tectonic Mega-Disasters Case Studies

• Tectonic mega-disasters are high impact, high magnitude hazard events which affect several countries either directly or indirectly

• Examples of mega-disasters include:

  • Asian tsunami (2004)

  • Eyjafjallajokull eruption, Iceland (2010)

  • Tohoku earthquake and tsunami, Japan (2011)

Table of Impacts