18.104.22.168 Most of these volcanoes are on the sea floor
and do not present a major hazard to people
with the exception of when they emerge above
sea level to form islands e.g. Iceland.
22.214.171.124 Rift valleys occur where the continental crust is being
stretched. For example the East African rift valley has a
line of 14 active volcanoes some of which can produce
violent and dangerous eruptions (Mt Nyragongo in DR
1.1.2 Destructive (Convergent) plate boundary
126.96.36.199 80% of the worlds volcanoes
occur along destructive plate
188.8.131.52 Oceanic - Oceanic, Soufriere
Hills in Montserrat.
184.108.40.206 Oceanic - Continental, Mt St
Helens in Washington.
Primary hazards - Collapse of buildings and infrastructure (water pipes/ gas supply)
Secondary hazards - Soil liquefaction, landslides, avalanches, tsunamis and exposure to adverse weather.
1.2.1 Destructive (Convergent) plate boundary
Continental - Continental
Oceanic - Oceanic
Continental - Oceanic
These are where the most frequent and highest magnitude earthquakes occur due to the force of compression as the plates meet, causing stresses in the crust. When the pressure is released the ground above shakes violently.
220.127.116.11 Features - Fold
1.2.2 Conservative (Transform) plate boundary
This is where lateral crust movement occurs, i.e. San Andreas Fault in California.
These produce frequent shallow earthquakes, sometimes of high magnitude.
1.2.3 Constructive (Divergent) plate boundary
These are usually submarine (Iceland is an exception) and are associated with shallow, low magnitude earthquakes as the crust pulls apart.
1.2.4 Other areas
18.104.22.168 A small minority of earthquakes
occur at intra-plate locations usually
as a result of old fault lines e.g.
Church Stretton fault in Shropshire.
22.214.171.124 Some earthquakes occur as a
result of human activity, e.g.
dam/resevoir building and fracking.
2.1.1 7th biggest killer, causing over
1400 deaths per year (more than
volcanoes or drought).
2.1.2 They occur in mountainous areas, after heavy rain
and after seismic activity. Human factors such as
deforestation and building on hillsides also increase
the risk of slides (Philippines)
2.2.1 Occur in high mountainous areas such
as the S. Alps of NZ or the Rockies in N.
America. Occur on slopes steeper than
2.2.2 150+ deaths per year
caused by avalanches.
2.2.3 Global warming may be increasing
avalanche occurrence. Trends in
deaths have slowed due to effective
3.1.1 Causes: Variation in the ITCZ which moves North
and south through Africa bringing a band of
seasonal rain. Sometimes high pressure zones
block rain to areas like Ethiopia and Somalia.
3.1.2 El Nino can cause major changes to
rainfall patterns, leading to drought in
Indonesia and Australia.
3.1.3 Changes in mid-latitude depression
tracks have caused droughts in UK
and France (1976, 1989-92, 1995,