This document summarizes different types of geologic hazards including earthquakes, volcanic eruptions, and landslides. It describes earthquakes as the shaking or trembling of the ground caused by displacement below the surface. Major earthquake hazards are ground shaking, ground rupture, tsunamis, liquefaction, landslides, and fires caused by gas line ruptures. Volcanic eruptions occur when pressure builds up inside a volcano, causing ash, gas and magma to be released. Associated hazards are lava flows, lahars, pyroclastic falls, volcanic gases, and tephra falls. Landslides involve the downward movement of earth materials along slopes, often caused by earthquakes or heavy rain. Specific landslide

1. GEOLOGIC HAZARDS

2. A geological hazard is a condition or event that may cause harm to property and
life as a result of a geological process such as earthquake, volcanic eruption, or
landslide.
A. Earthquake
01
B.Volcanic
Eruption
02
Landslides
03

3. A. Earthquake
An earthquake is a feeble shaking to violent trembling of the
ground produced by the sudden displacement of rocks or rock
materials below the earth’s surface. There are two types of
earthquakes: tectonic and volcanic earthquakes. Tectonic
earthquakes are those generated by the sudden displacement
along faults in the solid and rigid layer of the earth. Earthquakes
induced by rising lava or magma beneath active volcanoes are
called volcanic earthquakes.

4. Most common earthquake-
related hazards
• Ground shaking is a disruptive up-down
and sideways movement or motion
experienced during an earthquake. Strong
ground shaking can cause objects to fall,
break windows among others.

5. •Ground rupture is displacement
on the ground due to movement
of fault. This will be experienced
by areas where fault passes
through (note not all cracks on
the ground that people see after a
strong earthquake are faults,
some may just be surficial cracks
because of ground failure).The
movement may have vertical and
horizontal component and may
be as small as less than 0.5
meters.

6. •Tsunami is a set of sea
waves resulting from the
disturbance of ocean floor by
an earthquake.This is a
series of giant sea waves
commonly generated by
under-the-sea earthquakes
and whose heights could be
greater than 5 meters.
•

7. •Liquefaction is a
process that transforms
the behavior of a body
of sediments from that
of a solid to that of a
liquid when subjected to
extremely intense
shaking.

8. •Earthquake-induced landslides are
failures in steep or hilly slopes
triggered by an earthquake. Loose thin
soil covering on the slopes of steep
mountains are prone to mass
movement, especially when shaken
during an earthquake

9. •Fire is caused by
rupture of gas lines
during ground shaking
and displacement. It
poses threat of
explosions which may
cause death and
destruction of property.

10. B.Volcanic Eruption
• Volcanic eruption happens
when materials such as
magma, ash, and gas are
released from a volcano due to
a buildup of pressure inside.
The effects of an eruption can
be on a local scale affecting the
areas near the volcano (e.g.
lava flow reaches nearby
towns) or on a global scale (e.g.
volcanic ash particles on air
change global temperature).

11. •Lahar is a mixture
of volcanic debris
and water that
flows at the slopes
of the volcano. It
destroys
infrastructures,
buries towns and
crops, and fills river
channels.
•

12. •
•Pyroclastic fall is a
mass of hot, dry
pyroclastic material
(mixture of ash and
dust) and hot gases. It
moves rapidly along the
ground surface. It buries
towns and causes burns,
injury, and damage
upon impact.
•

13. •
•Volcanic gases are vapors
released during an eruption.
Some of these gases, such as
hydrogen sulfide (H2S) and sulfur
dioxide (SO2), are poisonous.
They cause respiratory damage
and death.
•

14. •Tephra falls are rock
fragments and lava
blobs ejected by a
volcano.They damage
structures, break power
lines, kill vegetation,
and cause respiratory
damage.

15. A landslide, also called landslip, occurs when earth
materials (rocks, debris, and soil) move downwards
along a slope. It may be caused by earthquakes or heavy
rainfall. It can also be aggravated by human activities
such as deforestation, blasting, and construction.
Landslide hazards are events associated with a
landslide that may cause adverse effects on organisms
and their environment.

16. •Mud flow is the flow
of mud and rock. It
may pick up trees,
houses, and cars as it
moves down the
slope. It may block
bridges and
tributaries causing
flood along its path.

17. Earthflow is the downward flow of fine-grained
materials, such as clay, fine sand, and silt. It is
slower than mudflow, but it inflicts the same
damage.
• Rock fall is the sliding, toppling, or falling of rocks along a
slope. It disrupts road traffic in mountainous regions. When it
hits a structure or vehicle, it causes damage depending on the
size of the rock and the force of impact