Distribution of hazards

Constructive:

Ocean ridges - Mid-atlantic Ridge. Mostly on sea floor. Only hazards to people when merge above sea level to form islands e.g. Iceland.

East African Rift Valley - line of 14 active volcanoes.

Destructive:

80% of worlds most active occur.

Oceanic plates subducted beneath continental plates.

Explosive volcanoes form e.g. Mt St.Helens + The Ring of Fire around the Pacific.

Landslides:

Mountainous areas after abnormally heavy rain or seismic activity.

Deforestation of hillsides in South East Asia and building on hills in Hong Kong - widespread slides following rain.

Snow Avalanches:

Global Warming may increase avalanches but deaths have slowed because of effective management.

High Mountainous Areas - Southern Alps of New Zealand or Rockies in North America (average of 100+ deaths per year)

Slopes steeper than 35'

Over 1/3 has exposure.

70% of worlds people and agriculture.

Causes: Variations in ITCZ - moves N and S through Africa; brings band of seasonal rain. High pressure zones expand and block rain-bearing winds.

Ethiopia and Somalia - famines.

El Nino - changes rain patterns; 2006 - drought in Australia & Indonesia.

Changes in mid-latitude depression tracks - Temperate regions = large amounts of rainfall.

If blocking anticyclones form - depressions track north = dry conditions; UK + France 2003 + 2006.

Evident in some 33% of the worlds area.

Regional scale, high-magnitude floods frequent in India/Bangladesh & China.

Causes = Excessive rain due to atmospheric processes - monsoon rainfall + cyclones. Series of depressions can lead to prolonged rainfall = flash flooding.

El Nino - Mosambique 1997/2006.

Snowmelt.

Latitudes 5-20' North/South of the Equator

Move Westward once generated

26'C Sea Temperature - 70m depth

5'N or South of equator so coriolis effect can bring rotation of air

Cause: Heavy rain/ High wind + Velocity/ Very low central pressure = storm surges and coastal flooding

Hotspots:

Volcanic hazards:
Most catostrophic are:

Localised areas of the lithosphere with an unusually high heat flow, magma rises to the surface as a plume e.g. hawaii.

As a lithospheric plate moves over a hotspot a chain of volcanoes is created.

Pyroclastic flows

Ash fall

Tsunamis

Mudflows; (1983 mudflows from nevado del ruiz killed over 22,000 people.)