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Types of Geological hazards
A geologic hazard has been defined as an extreme natural events in the crust of the earth that pose a threat to life and property, for example, earthquakes, volcanic eruptions, tsunamis (tidal waves) and landslides.
(OECD Glossary of Statistical Terms – Geologic hazard Definition https://stats.oecd.org › glossary › detail)
Overall there can be a distinction between weather events and Geological Hazards
- Geological Hazards are ones that link directly to geological processes and extra terrestrial events that affect human and animal populations and associated plant life and,
- Weather events and biological hazards It can be argued that these events may be exacerbated due to higher populations and human- induced global changes that affect climate and land degradation .
- There is a causal link between earth movements that cause earthquakes and volcanoes that link downslope to movement of rock and soil material. Ash flows and falls from volcanoes can form lahars (volcanic mud flows), landslips and landslides. Similarly movement along oceanic plate fault lines causes earth quakes and locally tsunamis on shorelines.
- These linked mechanisms also are assisted in their propagation by the action of weather and human movement to higher risk areas
- Rainfall that lubricates the unstable moving landscapes – examples mainly are from collisional terranes and associated stratovolcanoes –e.g. Vesuvius, Mount St Helens and Tavurvur
- The main examples are the volcanoes along the oceanic ridges (Mid Atlantic and east Pacific Rise) and the East African Rift
- Iceland receives thousands of earthquakes associated with the Mid Atlantic ridge that essentially is slowly splitting the island in two.
- Volcanoes in extensional zones are more predictable hazard to humanity than those in convergent margins and generally pose less immediate risk to communities
- Humanity has taken a risk mitigation approach to weather events as it is powerless to influence them directly
Hazards on earth can also be subdivided into Geological hazards and weather events (see module 10 page)
This does not account for the affect of local weather events created by volcanic eruptions and the effect of weather events in activation geological hazards.
- iceland the splitting of the North American and Eurasian plates
|Geological hazards||Weather events and biological hazards|
|Earth Movements Earthquake, Volcanic eruption, Lahar, Avalanche, Landslide, tsunamis, Sinkhole, meteor and asteroid collisions||Weather events and Climate – Blizzard, Drought, Hailstorm, Heat wave, Cyclonic storm, Ice storm, Tornado (water spout),
Bushfires and Wildfire
Disease and global pandemics
Earth Movements such as quakes, eruptions, lahars (volcanic mudflows) and tsunamis extra-terrestrial collisions with earth are generally out of human control and management, but can be exacerbated by human activities. For example avalanches and landslips can be made worse by human removal of vegetation and disturbance of unstable slopes.
Biological hazards including bacteria, viruses, epidemics and pandemics
Bacterial disease that have affected human populations as well as viruses. Major events have included Pneumonia, meningitis, and food poisoning. Throughout history, millions of people have died of diseases such as bubonic pljor kille4rs have beenague or the Black Death, which is caused by Yersinia pestis bacteria and smallpox, which is caused by the variola virus. In recent times, viral infections have been responsible for two major pandemics: the 1918-1919 “Spanish flu” epidemic that killed 20-40 million people, and the ongoing HIV/AIDS epidemic that killed an estimated 1.5 million people worldwide in 2013 alone. and the EBOLA SARS MERS and CORONA viruses in the 21st century. These three latter viruses have been Caused by encroachment of humanity on wild lifeabitats and populations
Major natural disasters
Using the definition above linking geohazards to the crust of the earth, there is a link to the major global natural disasters affecting life and property. Lightning causing death and fire is a natural phenomenon that in extreme situations be generated by large fire fronts. The major hazards are:
- 7 Landslides.and natural hazards
- 6 Volcanic eruptions.
- 5 Tornadoes.
- 4 Lightning.
- 3 Tsunamis.
- 2 Hurricanes.
- 1 Earthquakes.
Of the major natural disasters listed above the effects some can be greatly exacerbated by human activity. For example landslides and land slips usually occur when hydrological (water saturation of a rock and soil) loading of the soil and rock mass on steep slopes is excessive. If these slopes have also been cleared or partially so due to human activities (including agriculture and mining) the landslide can be far more destructive as the rock and soil mass becomes over saturated and will form a sheet like dense flow carrying thick mud and rocks and burying all in its path. There are numerous examples of this occurring in Latin America. Major landslips can occur im regions that have an unstable substrate such as regions affected by the movement of ice across a landscape that can create clays that can liquefy whne saturated to form a glide plane for large areas of land such as the one in Norway in early June 2020
Meteors and extra-terrestrial collisions
- Extra-terrestrial collisions are a source for major concern when they occur.
- These have created local and global extinctions of plants and animals and the Cretaceous age comet that collided with the earth has been linked to the extinction of the dinosaurs
- The large amount of water on the earth is also linked to collisions with the primitive earth Scientists predict that the water in Earth’s oceans came from water-carrying bodies in the early solar system that collided with our planet, similar to today’s ice-rich asteroids or comets. But scientists do not know where in the formative disk these objects originated.