Geohazards are natural hazards caused by geological processes of the Earth, such as earthquakes, volcanoes, floods, landslides, and tsunamis. These events can cause significant loss of life and property damage when they occur. Some geohazards like volcanoes and cyclones may be predicted by monitoring warning signs like changes in gases, small earthquakes, and swelling of the volcano. Major earthquakes typically occur along fault lines and are followed by aftershocks. Volcanic eruptions pose hazards from pyroclastic flows, lahars, and tsunamis they can trigger. Landslides involve the breakdown and downhill movement of rock and debris. Tsunamis are gravity waves

1. GEOHAZARDS
Everything you need to know about Geohazards
by Jevish Sydamah…

2. WHAT IS GEOHAZARDS?
 A Geohazard is any natural hazard that is caused by the Earth, for example volcanoes, earthquakes,
floods, tsunamis and cyclones. These and other Geohazards can cause great loss of life and damage to
property when they occur so governments are always looking for ways of reducing the impacts of
Geohazards. It is sometimes possible to predict when certain Geohazards will occur, such as volcanoes and
cyclones. For example the eruption of a volcano can be predicted when scientists observe the following
warning signs:
 1. The gases that volcanoes give off suddenly change.
 2. Small earthquakes happen in the local area.
 3. The volcano starts to get bigger as it fills with magma.

3. EARTHQUAKES
 Earthquakes: Fractures in Earth's crust, or lithosphere (its crust and upper
mantle), where sections of rock have slipped past each other are called faults.
Earthquakes are caused by the sudden release of accumulated strain along these
faults, releasing energy in the form of low-frequency sound waves called seismic
waves. A major earthquake are usually followed by aftershocks. The epicentres of
large earthquakes are normally located along known seismically active zones,
although the disruptive effects of an earthquake may extend over areas 100s of
kilometres away. Earthquakes may cause liquefaction, landslides, marine landslides
and tsunamis.

4. VOLCANOES
 Volcanoes: A volcano is defined by an opening in the Earth's crust
from which lava, ash, and hot gases flow or are ejected during an
eruption. Volcanic hazards vary from one volcano to another and from
one eruption to the next. The big killers are pyroclastic flows, lahars, and
tsunamis triggered by volcanic eruptions. The most frequent lethal events
are so-called tephra explosions – very rapid jets of lava . The longest-
lasting damage is usually inflicted by thick lava flows or major collapses of
volcanic edifices, as at Mt. St. Helens in 1980.

5. LANDSLIDES
 Landslides: A landslide is a Geohazard that involves the breakup and downhill flow
of rock, mud, water and anything caught in the path. Landslides are one of the main
processes by which landscapes evolve and the related hazards result in a complex,
changing landscape. Landslides both vary enormously in their distribution in space and
time, the amounts of energy produced during the activity and especially in size. This
means that the resulting surface deformation or displacement varies considerably from
one type of instability (that trigger the breakup) to another. Individual ground instabilities
may have a common trigger, such as an extreme rainfall event or an earthquake, and
therefore occur alongside many equivalent occurrences over a large area. This means that
they can have a significant regional impact.

6. TSUNAMIS
 Tsunamis: Tsunamis are gravity waves (different physical features
than wind induced surface waves) created by a rapid displacement of a
water column. The displacement can be the result of earthquakes,
volcanic eruptions or landslides. These energetic waves travel fast with
long wavelengths and relatively small amplitudes in open ocean. When
hitting shallow water they build up an amplitude and can become tens,
and on very rare occasions, even hundreds of meters high. The coastal
inundation can be devastating and catastrophic.

7. EXTREME GEOHAZARDS
 Extreme Geohazards
The Sumatran earthquake/Indian ocean tsunami was one of the most extreme
Geohazard in modern history . This extreme reached us all, beyond the mere geophysical
waves. As tourists come from all over the world to visit the beautiful shores of the Indian
ocean, the 2004 tsunami affected people from around the globe. The extent of it's
destruction and the dimension of the disaster are parts of the definition of extreme.
That, combined with their physical features that normally are several orders higher or
more powerful than the average Geohazard. So, when we talk about extreme Geohazards
we not only refer to the physical characteristics of the Geohazard but also the risk they
represent in terms of consequences of this hazard.

8. MEGA TSUNAMIS AND
SUPER VOLCANOES
 Really extreme Geohazards – mega tsunamis and super volcanoes
Norway is situated in a safe distance from the Ring of Fire. Crustal movements in
this part of the world are very slow stemming from post glacial rebound, the uplift
of ground due to the absence of heavy glaciers that melted thousands of years ago.
Norway has in fact a rather high number of earthquakes as well but these far from
qualify as extreme Geohazards. But, if we look at the geological history of Norway
we find evidence of a really extreme Geohazard. More than 8000 years ago, the
submarine Storegga landslide caused a wide ranging mega tsunami hitting most of
our entire coastline.

9. EXAMPLE OF A
GEOHAZARD
 Submarine) Landslides
 Debris flows
 Shallow gas accumulation
 Overpressured zones (including gas and shallow water flows)
 Naturally occurring gas hydrates and their climate-controlled meta-stability
 Mud flows, diapirism and mud volcanism/mud volcanoes
 Earthquakes and seismicity
 Tsunamis from tectonics and landslides
 Rock falls and landslides

10. STATS CAUSED BY
GEOHAZARDS
 The World Disasters Report 2005 estimated that in 2004, over 250,000 were reported
killed by natural disasters—mostly from the Indian Ocean tsunami in December.
Disasters affected 146 million persons and inflicted estimated damage of US$ 100-145
billion. From 1995 to 2004, about 6,000 reported disasters killed over 900,000, affected
over 2.5 billion persons, and caused at least US$ 738 billion in estimated damage . This
compares to 640,000 reported killed and 1.74 billion reported affected by natural disasters
from 1985 to 1994. Over the decade, 51 people died per natural disaster event in
countries of high human development (as defined by United Nations Development
Program), compared to 573 deaths per event in countries of low human development.

11. PHOTOS…

12. STRUCTURE…

13. GEOHAZARD RESOURCE…

14. VOLCANO…

15. LANDSLIDE…

16. TSUNAMI…

17. EARTHQUAKE…

18. HOPE YOU ENJOYED THE
PRESENTATION.
THANK YOU FOR
READING…
BY JEVISH SYDAMAH