The Planet Earth Geohazard
Interior Structure of the Earth Geo – “geological” meaning from earth
- Earth radius: 6371 km, although Hazard – a situation that poses a risk to
larger at equator than at poles property, environment or life
- Density (mass/volume), temperature,
Geohazard – means the risk of damage
and Pressure increase with depth in
caused by a geological process.
the earth.
- The Earth has a layered structure and Natural Hazard – are defined as
is viewed in two different ways: (1) environmental phenomena that have the
layers of different chemical potential to impact societies and the human
composition, and (2) layers of environment.
differing physical properties. - Can also cause secondary natural
- Compositional layering: hazard events that create additional
o Crust – low density silicate hazards. Ex. Volcanic activity can
rocks create other hazards, such as ash and
▪ Continental – 10-70km lava spread.
thick - Natural hazard is the threat of an
▪ Oceanic – 8-10 km thick event that will likely have a negative
o Mantle – 3488 km thick, made impact.
up of a rock called peridotite - Natural Disaster – is the negative
o Core – 2883 km radius, made impact following an actual occurrence
up of Iron (Fe) with some of natural hazard in the event that it
Nickel (Ni) significantly harms a community.
- Physical Properties - Avalanche, Drought, Earthquake,
o Lithosphere – 100 km thick (up Hurricane, Landslide, Lightning,
to 200 km thick beneath Tornado, Tsunami, Volcanic activity,
continents), very brittle, easily Wildfire
fractures at low temperature
o Asthenosphere – about 250 km Man-made Hazards
thick – solid rock, but soft and - Events that are caused by humans
flows easily (ductile) and occur in close to human
o Mesosphere – about 2500 km settlements
thick, solid rock, but still - The events leading up to a man-made
capable of flowing hazard may be the result of deliberate
o Outer Core – 2250 km thick, Fe or negligent human actions, but their
and Ni, liquid impact can be equally as devastating.
o Inner Core – 1230 km radius, Fe
and Ni, solid
, - Ex.: Toxic wastes, Dam failures, Fires, Introduction to Volcanoes
Chemical spills, Industrial pollution,
What is a volcano?
Ionizing radiation
- A vent, hill or mountain from which
Why is it important to study geohazard?
molten or hot rocks with gaseous
- Geologic hazards are responsible for material have been ejected
great loss of life and destruction of - Craters, depressions, hills or
property. Data on hazards, exposures, mountains formed by removal of pre-
vulnerabilities, and losses enhance existing material or by accumulation
the accuracy of risk assessment, of ejected materials.
contributing to more effective -
measures to prevent, prepare for and
The Nature of Volcanic Eruptions
financially manage disaster risk.
What determines whether a volcano
extrudes magma violently or gently?
Magma’s composition, temperature, and
dissolved magma it contains – these factors
affect magma’s viscosity.
Magma associated with an explosive
eruption may be five times more viscous
than magma that is extruded in a quiescent
manner.
- The more silica in magma, the greater
its viscosity.
Why does the Philippines have many
volcanoes?
- The Philippine sits on a unique
tectonic setting ideal to volcanism
and earthquake activity. It is situated
at the boundaries of two tectonic
plates – the Philippine Sea plate and
the Eurasian plate – both of which
subduct or dive beneath the
archipelago along the deep trenches
along its east and west seaboard.
Shield Volcanoes- Shield volcanoes are
produced by the accumulation of fluid
Interior Structure of the Earth Geo – “geological” meaning from earth
- Earth radius: 6371 km, although Hazard – a situation that poses a risk to
larger at equator than at poles property, environment or life
- Density (mass/volume), temperature,
Geohazard – means the risk of damage
and Pressure increase with depth in
caused by a geological process.
the earth.
- The Earth has a layered structure and Natural Hazard – are defined as
is viewed in two different ways: (1) environmental phenomena that have the
layers of different chemical potential to impact societies and the human
composition, and (2) layers of environment.
differing physical properties. - Can also cause secondary natural
- Compositional layering: hazard events that create additional
o Crust – low density silicate hazards. Ex. Volcanic activity can
rocks create other hazards, such as ash and
▪ Continental – 10-70km lava spread.
thick - Natural hazard is the threat of an
▪ Oceanic – 8-10 km thick event that will likely have a negative
o Mantle – 3488 km thick, made impact.
up of a rock called peridotite - Natural Disaster – is the negative
o Core – 2883 km radius, made impact following an actual occurrence
up of Iron (Fe) with some of natural hazard in the event that it
Nickel (Ni) significantly harms a community.
- Physical Properties - Avalanche, Drought, Earthquake,
o Lithosphere – 100 km thick (up Hurricane, Landslide, Lightning,
to 200 km thick beneath Tornado, Tsunami, Volcanic activity,
continents), very brittle, easily Wildfire
fractures at low temperature
o Asthenosphere – about 250 km Man-made Hazards
thick – solid rock, but soft and - Events that are caused by humans
flows easily (ductile) and occur in close to human
o Mesosphere – about 2500 km settlements
thick, solid rock, but still - The events leading up to a man-made
capable of flowing hazard may be the result of deliberate
o Outer Core – 2250 km thick, Fe or negligent human actions, but their
and Ni, liquid impact can be equally as devastating.
o Inner Core – 1230 km radius, Fe
and Ni, solid
, - Ex.: Toxic wastes, Dam failures, Fires, Introduction to Volcanoes
Chemical spills, Industrial pollution,
What is a volcano?
Ionizing radiation
- A vent, hill or mountain from which
Why is it important to study geohazard?
molten or hot rocks with gaseous
- Geologic hazards are responsible for material have been ejected
great loss of life and destruction of - Craters, depressions, hills or
property. Data on hazards, exposures, mountains formed by removal of pre-
vulnerabilities, and losses enhance existing material or by accumulation
the accuracy of risk assessment, of ejected materials.
contributing to more effective -
measures to prevent, prepare for and
The Nature of Volcanic Eruptions
financially manage disaster risk.
What determines whether a volcano
extrudes magma violently or gently?
Magma’s composition, temperature, and
dissolved magma it contains – these factors
affect magma’s viscosity.
Magma associated with an explosive
eruption may be five times more viscous
than magma that is extruded in a quiescent
manner.
- The more silica in magma, the greater
its viscosity.
Why does the Philippines have many
volcanoes?
- The Philippine sits on a unique
tectonic setting ideal to volcanism
and earthquake activity. It is situated
at the boundaries of two tectonic
plates – the Philippine Sea plate and
the Eurasian plate – both of which
subduct or dive beneath the
archipelago along the deep trenches
along its east and west seaboard.
Shield Volcanoes- Shield volcanoes are
produced by the accumulation of fluid
