The focus is the first point of Earth's movement during an earthquake because that is where the rupture or slip along the fault initiates. The focus is the point within the Earth where the strain accumulated along the fault is first released, causing the rocks on either side of the fault to suddenly shift and cause the seismic waves that make up the earthquake. So the focus marks the hypocenter or origin point where the earthquake energy is generated.

1. Geological Hazards

2. Geologic hazards are naturally occurring geologic
conditions that can cause immense damage to
properties and loss of lives.

3. Earthquake
● This is the sudden
movement of Earth’s crust
that results from the
release of accumulated
strain from tectonic and
volcanic activities.
Earthquakes can cause damage
to structures.

4. Parts of an Earthquake
● Hypocenter or focus refers
to the actual location of the
first motion that causes the
earthquake
● Epicenter is the point on
Earth’s surface directly
above the focus.
● Faults are planes of fracture
in rock bodies. Parts of an earthquake

5. Effects of an Earthquake
● Ground shaking is the vibration of the ground during an
earthquake.
● Liquefaction is where soil loses strength temporarily and
behaves as a liquid.
● Surface faulting is the tearing of the ground surface
caused by displacement along faults during earthquakes.

6. Volcanic Eruptions
● Volcanic eruption is
the discharge of
materials and gas
from the interior of
the volcano to the
surface and to the
atmosphere.
Alert levels for Mayon volcano

7. Movement of Materials:
Volcanic Eruptions
● Basal flow is a dense
mixture of gas, ash and
volcanic rocks.
● Turbulent ash cloud
includes pyroclastic surges
and columns of ash.
● Lahar is a catastrophic
mudflow on the slopes of
volcanoes. Lahar

8. Landslides
● Landslides or mass
wasting is the general
term that refers to the
movement of Earth
material down slopes.
A mudflow in Brazil.

9. Landslide Types
● Rockfall is the fall of
unconsolidated material.
● Earthflows occur when
water seeps into the soil
and bedrock causing
breakage and flow.
● Mudflows are composed of
a mixture of water and
volcanic materials.
Rockfall in Afghanistan

10. Tsunami
● Tsunamis are created
by weather
disturbances such as
an earthquake,
landslide, volcanic
eruption, or meteorite.
● A series of waves is
formed. A tsunami in Thailand.

11. Earthquake is the sudden movement of Earth’s crust
caused by movements along faults.
1
Volcanic eruptions may cause pyroclastic flows and
lahar and may release toxic gases.
2
Landslides may be in the form of mudflow, earthflow
or rockfall. All can impose danger to human lives and
structures.
3

12. Read and analyze the following statements given
below. Identify the word or words being described
by each statement.
1.This is composed of mixture of water and volcanic materials that are
fast moving outflows.
2.It is the movement of Earth material down slopes.
3.This is a composition of pyroclastic flows that are characterized by
dense mixture of gas, ash, and volcanic rock.
4.It is the amount of energy released by earthquake.
5.These are formed on hillsides during heavy rains or melting of snow.

13. Why is the focus the first point of Earth’s
movement?