This shows the distribution of hazards and their various causes and impacts; hazards are divided into Geophysical as they have to do with tectonic processes and hydro-meteorological as it involves the climate
Earthquakes- Most earthquakes are concentrated around plate boundaries; the more powerful earthquakes are located along destructive or conservative plate boundaries. As in a conservative plate boundary the plates are parallel to the plate margin so they slide past each other and for a destructive plate boundary the plates are converging.
The fundamental explanation of their occurrences as with geophysical hazards has to do with the knowledge of plate tectonics. At destructive plate boundaries, oceanic crust are being subducted beneath a continental plate it produces various earthquakes types. The force as the plates meet causes stresses in the crust, then its pressure is suddenly released causing the ground above to shake violently thus resulting in what is formerly known as an earthquake. Also, by conservative plate boundaries the magnitude varies from shallow to quite high; this is true of the San Andreas Fault, Western USA.
Furthermore, earthquakes are also located around constructive plate boundaries but are associated with low magnitude earthquakes so they pose little hazard to people.
Volcanoes- Distribution of Volcanoes is global, although they are usually perceived to only occur on plate boundaries; however this is not always the case. Sometimes they can occur on faults or ancient faults like Mt Etna. This is still active because the fault line it used to lie on still provides it with magma.
The active volcanoes are found along three tectonic areas; the constructive and destructive plate boundaries, and at hotspots. The main volcanoes are located along the destructive plate boundaries, as when two plates collide and the oceanic plate is subducted beneath continental plates explosive volcanoes are formed. Examples include Mt St Helens in Northwestern USA and the Soufriere Hills in Montserrat.
Volcanoes can also be present at hotspots; which are localized areas of the lithosphere which have an unusual high heat flow, for example, the volcanic Hawaiian Islands. However the largest and most fatal volcanoes are primarily on plate boundaries, sometimes concentrated in a certain area, like the “Ring of fire” on the Pacific plate and its surrounding plates. These volcanoes often occur due to spreading ridges, causing gaps which magma flows up. Volcanoes in this area usually follow earthquakes, which are also more frequent here than on faults.
Tsunami – associated with earthquakes and only affect coastal areas e.g. Hawaii and Indonesia.
Flood – are mostly due to excessive rainfall associated with atmospheric processes, so are distributed where this is common; these areas where monsoon rain and cyclones are widespread. In temperate climates like the UK prolonged high rainfall are as a result of series of depressions. Moreover, the El Nino Southern Oscillation whereby there are temperature fluctuations in the surface waters of the Eastern Pacific Ocean can bring about devastating floods, as in Mozambique. Also, floods could be due to rapid thaw of accumulated snow adding water to a full river system.
Drought – have a dispersed pattern as a high percentage of the world’s land surface has some level of drought exposure. The El Nino can bring about major changes to rainfall patterns thus bringing about drought conditions to Indonesia and Australia. In temperate regions, depressions bring about large amounts of rainfall. However if anticyclones form and persist depressions are forced to track further north, leading to very dry conditions. Examples include the droughts in the UK and France in 2003 and 2006 etc. Furthermore, movement in the Inter tropical convergence zones brings a set of seasonal rain and high pressure zones might block the rain bearing winds thus leading to droughts.
A secondary effect of a drought is Fire, also known as Wildfires. A wildfire is an uncontrolled fire often occurring in wild land areas, but which can also consume houses or agricultural resources. They are common in much of the world where the climates are sufficiently moist to allow the growth of trees, but feature dry, hot periods when fallen branches, leaves and other material can dry out and become highly flammable. Wildfires are also common in grasslands and scrublands. Examples include Western USA and Australia.
Hurricanes – are violent storms between 200 and 700km in diameter, occurring in latitudes 5-20 degrees north and south of the equator and once generated, they tend to move westward. They mostly occur over warm oceans in order that the Coriolis effect can cause the rotation of air.
Both [ Geophysical and Hydro-meteorological
Avalanches & Landslides – areas prone to landslides are mountainous and experience landslides after abnormally heavy rain and or seismic activity.
Moreover, avalanches are concentrated in high mountainous areas such as Southern Alps of New Zealand or the Rockies of North America.