Lesson 1 - Potential Volcanic Hazards

24 ACTIVE VOLCANOES AS OF 2025

• how many active volcanoes does Philippines have?

VOLCANO

• is an opening in the earth’s crust through which lava, volcanic ash, and gases escape.

• Pressure build sup inside the magma chamber, causing the magma to move through channels in the rock and escape onto the planet’s surface

MAGMA

• inside an active volcano is a chamber in which molten rock, called___ collects

LAVA

• once the rock escapes onto the planet’s surface and it allows onto the surface, the magma is known as  ___

FORMATION OF VOLCANOES

1.Volcanoes form when magma (molten rock) from inside the Earth comes to the surface.

2.Magma comes from The upper mantle beneath the Earth's crust.

3.At subduction zones, one tectonic plate moves under another, causing melting that creates magma.

4.The magma erupts as lava and ash, which pile up on the surface.

5.These layers of lava and ash build up over time to form a volcano mountain.

1.LAHAR
2.ASHFALL
3.PYROCLASTIC FLOW
4.BALLISTIC PROJECTILES
5.VOLCANIC GASES
6.LAVA FLOW

• six components of volcano-related hazards

LAHAR

• means a muddy flow of volcanic material mixed with water.

• It carries fresh volcanic debris like ash and pyroclastic materials, plus older materials from rivers and water channels.

• It can bury houses and is deadly because of its thickness and toxic chemicals.

• Lahars usually form in areas with water channels and follow paths of volcanic debris flows.

• Lahar moves very fast, up to tens of meters per second, making it impossible for people to outrun.

• Large boulders carried by lahars can be found scattered, showing past lahar activity in an area.

• The formation of the wet cement-like structure of lahar does not always come from rivers and water channels. Oftentimes, intense rainfall may also bring out the formation of lahar.

• Volcanoes release various toxic gases and materials up the atmosphere that affect the weather in the area. In turn, this leads to a lot of rain, lightning, and thunder.

ASHFALL

• is made of tiny volcanic particles less than 2 mm called ash, which falls after an eruption.

• After an eruption, ash rises in a column and then falls, covering nearby areas.

• can cause health problems like breathing difficulties and skin damage.

• It can contaminate water sources, making them toxic.

• can also damage buildings, infrastructure, the environment, and aircraft.

• Example: The 2020 eruption of Taal Volcano caused harmful ashfall affecting nearby

communities.

TEPHRA

• is a general term for all volcanic fragments, including ash.

PYROCLASTIC FLOW

• are fast-moving currents of hot volcanic particles, gases, and ash that come from a volcano after an explosion.

• They are part of what is called pyroclastic density currents (PDCs)

PYROCLASTIC DENSITY CURRENTS (PDCs)

• hot, fast-moving clouds of ash, gas, and rock fragments that surge downslope.

BALLISTIC PROJECTILES

• are large volcanic blocks or bombs thrown from a volcano during an eruption.

• They land 2-5 km away from the volcano but can travel farther if the eruption is strong.

• These projectiles act like cannonballs and can create small craters where they land.

• They carry hot, partially molten lava that can cause fires or explosions if they hit homes or people.

VOLCANIC GASES

• Volcanic eruptions release many gases before,

during, and after the eruption.

• These gases come out through vents, fumaroles, and hydrothermal systems.

• Some gases are heavier than air and can settle in low areas, harming people and animals nearby.

1.WATER VAPOR
2.CARBON DIOXIDE
3.SULFUR DIOXIDE
4.HYDROGEN SULFIDE
5.HYDROGEN HALIDES

• common gases and their effects

WATER VAPOR

• Harmless, colorless, and most abundant gas.

CARBON DIOXIDE (CO2)

• Colorless and odorless; high levels in low areas can cause

  headaches, dizziness, breathing problems, and can be fatal.

SULFUR DIOXIDE (SO2)

• Colorless with a strong smell; irritates skin, eyes, and lungs; can

  create smog harmful to communities.

HYDROGEN SULFIDE (H2S)

• Smells like rotten eggs; toxic and can cause unconsciousness and death in high amounts.

HYDROGEN HALIDES (HF, HCl, HBr)

• Toxic acids that form acid rain, harming water

sources and plants.

LAVA FLOW

• are bright red-orange because they are molten rocks coming from a volcano.

• Lava moves down slopes from eruption vents.

• The amount of silica in lava affects how thick (viscous) it is.

• Low silica lava has low viscosity and moves very fast, sometimes kilometers per hour.

• Steeper slopes make lava flow even faster due to gravity.

• Lava flows are very hot and can cause forest fires.

• They can burn soil, plants, houses, and buildings, creating dangerous rivers of lava.

SIGNS OF AN IMPENDING VOLCANIC ERUPTION

1.  More frequent and stronger earthquakes happen near the volcano as pressure builds underground.

2. Steam and gases coming out from vents near the volcano increase, sometimes seen as clouds.

3. Fumaroles (gas vents) release more gases, especially carbon dioxide.

4. The area’s temperature rises, showing magma is getting closer to the surface.

5. The ground near the volcano tilts, cracks, or lifts as rocks are pushed up.

6. Lava may appear at the volcano’s opening, showing magma is escaping.

7. Vegetation may change color due to more volcanic gases.

8. Landslides can occur because of volcanic activity.

9. Nearby springs or water sources may dry up.

HAZARD MAP

• serve as a guide to people about the danger ones and safe zones in the vicinity of the volcano. The maps may change from time to time depending on the activity of the volcano

1.ALBAY (MAYON VOLCANO)
2.BATANGAS (TAAL VOLCANO)
3.CAMIGUIN (HIBOK-HIBOK VOLCANO)
4.SORSOGON (BULUSAN VOLCANO)
5.NEGROS OCCIDENTAL (ANLAON VOLCANO)
6.PAMPANGA (PROXIMITY TO MOUNT PINATUBO)
7.CAVITE (AFFECTED BY TAAL VOLCANO)
8.IFUGAO (NEAR VOLCANIC HAZARD ZONES)
9.NORTHERN SAMAR (VOLCANIC ACTIVITY EXPOSURE)
10.MASBATE (VOLCANIC INFLUENCE)

• top 10 provinces with the most active volcanoes/affected

1.LAHAR HAZARD MAP
2.ASHFALL HAZARD MAP
3.PYROCLASTIC FLOW HAZARD MAP
4.BALLISTIC PROJECTILE HAZARD MAP
5.VOLCANIC GASES HAZARD MAP
6.LAVA FLOW HAZARD MAP

• interpreting hazard maps

ALERT SIGNALS

• there are various recommended actions per alert level warning

• communities must never be complacent in applying extra measures for protection and evacuation since volcanoes are highly unpredictable

1.0 (NO ALERT)
2.1 (ABNORMAL)
3.2 (INCREASING UNREST)
4.3 (INCREASED TENDENCY TOWARD HAZARDOUS ERUPTION)
5.4 (HAZARDOUS ERUPTION IMMINENT)
6.5 (HAZARDOUS ERUPTION)

• Mayon Volcano Alert Signals

0 (NO ALERT)

• quiet

• no eruption in foreseeable future

1 (ABNORMAL)

• low-level unrest

• no eruption imminent

2 (INCREASING UNREST)

• moderate unrest

• unrest probably of magmatic origin; could eventually lead to eruptions

3 (INCREASED TENDENCY TOWARD HAZARDOUS ERUPTION)

• relatively high unrest

• magma is close to the crater

4 (HAZARDOUS ERUPTION IMMINENT)

• intense unrest

• hazardous eruption is possible within days

5 (HAZARDOUS ERUPTION)

• hazardous eruption ongoing

• pyroclastic flows may sweep down a long gullies and channels, especially along those fronting the low part(s) of the crater rim.

STAND-DOWN PROCEDURES

• alert levels will be maintained for the following periods after activity decreases to the next lower level

• From level 5 to level 4: wait for 12 hours after level 5 activity stops

• from level 4 to level 3 or 2: wait for 2 weeks after the activity drops below level 4

• from level 3 to level 2: wait for 2 weeks after the activity drops below level 3