DRRR Reviewer 3rd Qtr

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Volcanic Eruptions

Volcanic Eruptions

- Because of the location of the Philippines (Pacific Ring of Fire), the landscape contains numerous volcanoes

- Tectonic plates undergo subduction in the form of trenches which contribute to the formation of the volcanoes

Volcano

- is the opening in the crust that ejects magma and forms a fissure and may be located on a mountain or ocean ridge

Magma chamber

- The source of the magma

Eruption

- caused by the build-up of heat and pressure within the volcano

Vent

- is the central opening of a volcano

Side vents

- are the openings on the side of the volcano

Branch

- Other pipes connected to the conduit

1. Active volcanoes

2. Dormant volcanoes

3. Extinct Volcanoes

3 Classification of Volcanoes

Active volcanoes

(Classification of Volcanoes)

- regularly erupt within the last 600 years

- include those volcanoes identified farther back in time to have erupted n the last 10,000 years

Mt. Mayon

– most active volcano

- 51 eruptions from 1616 to 2014

- most destructive occurred in 1814 with at least 1200 fatalities

Mt. Pinatubo

– one of the biggest eruption

- 1991 eruption has led to more than 700 fatalities

- considered as the second largest eruption of the 20th century

Tambora

- the largest eruption of the 20th century

Taal Volcano

– one of the most active volcanoes

- 33 eruptions since 1572

- its crater is filled with water creating a lake

Dormant volcanoes

(Classification of Volcanoes)

– erupted in the last 10,000 years but may still erupt in the future

- Mt. Pinatubo in Zambales, Philippines

Extinct Volcanoes

(Classification of Volcanoes)

– no record of eruptions; they may not be completely extinct due to their emission of sulfur

- Mt. Arayat in Arayat, Philippines

1. Lava Flow

2. Dome Growth

3. Pyroclastic Flow

4. Pyroclastic Surge

5. Ballistic Projectiles

6. Tephra fall

7. Volcanic Gases

8. Lahar

8 Volcanic Hazards

Lava Flow

- Cascading lava (surface magma) in the form of streams from the erupting vent down the slope

- lesser viscosity and faster movement

Dome Growth

- Formation of lava dome from viscous magma that solidified along the vent

Pyroclastic Flow

- Composed of an extremely hot mixture of rock fragments, expanding gases, and ashes with a temperature greater than 800 °C

- moves at 10m/s to 200m/s

Pyroclastic Surge

- Same as pyroclastic flow; has less rock but more gases

- average temperature of 100 °C

- cold surge can take place in volcanoes underneath the ocean or lake

Ballistic Projectiles

- Happens due to the built-up gas pressure that quickly launches the volcanic materials (volcanic bomb) bigger than 64mm up in the air

Tephra fall

- Any rock fragment or material ejected during a volcanic eruption that contains:

▪ ash (less than 2mm)

▪ lapilli (2 to 64mm)

▪ blocks

▪ bombs

Volcanic Gases

- mixture of gases that include water vapor, hydrogen sulfide, sulfur dioxide, carbon monoxide, hydrogen chloride, and hydrogen fluoride that affects the temperature

Lahar

- “mudflow” or “volcanic debris flow”

- composed of mixture of volcanic debris and water that has the consistency of wet concrete and it moves down the slope and find its way into the rivers

Volcanic Hazard Maps

- Utilized to provide information on the potential damaging effects of an eruption that can be used as a basis for disaster mitigation plans of a locality

Landslides

- The bulk movement of rock, debris, or earth down a tilted land due to gravity

1. Geological

2. Morphological

3. Human activities

3 Factors of Landslides

Geological

- refers to particular features of the material making up the slope

- involves physical characteristics of the rock, mineral composition, and features of the slope

Morphological

- land structure is considered under this type of cause

- decreased vegetation, fire, drought, presence of trees, earthquakes, volcanic eruptions, erosion, weathering, and heavy rainfall are other morphological causes

Human activities

- the impact of human activities aggravate the conditions; deforestation, land development, and construction, irrigation, mining, and water leakage

1. Flow

2. Topple

3. Slump

4. Slide

5. Creep

6. Fall

6 Types of Landslides

Flow

- High speed due to the fluidity and consistency

1. Debris flow

2. Mudflow

3. Mudslide

3 types of Flow

Debris flow

- Type of flow composing of loose soil, rock, organic matter, and water

Mudflow

- Type of flow composing of at least 50% sand, silt, and clay

Mudslide

- Combination of debris flow and mudflow

Topple

- Tumbling over blocked units due to gravity

Slump

- Sliding mass movement of materials along an arched portion of the slope

Slide

- Happens along weak portions of the slope such as faults, join, or bedding plane

- motion is parallel to the slope

Creep

- Unnoticeable gradual motion of materials

Fall

- Free-falling of materials (bouncing or rolling)

Sinkhole

- Depression of the land

- Opening in the ground that is a result of the dissolving of rocks beneath the surface or the collapse of the cave

- Varies in size and depth

- Often created in places where groundwater can readily dissolve particular types of rocks

1. Weathering

2. Erosion

3. Heavy rainfall

4. Drought

5. Earthquake

5 Natural Events that Trigger Sinkholes

1. Excessive groundwater pumping

2. Placement of heavy structures and equipment

3. Water leakage from sewer pipes

4. Construction of wells, dams, and ponds

5. Soil excavation, drilling, mining, and quarrying

Human Activities that Trigger Sinkholes

1. Dissolution sinkhole

2. Cover subsidence sinkhole

3. Cover-collapse sinkhole

3 Types Sinkholes

Dissolution sinkhole

- can turn into a pond due to surface runoff

- has carbonate bedrock

Limestone-solution sinkhole

Dissolution sinkhole is also called ---

Cover subsidence sinkhole

- Created by sediments filling in the cavities within the bedrock

Quicksand

Cover subsidence sinkhole is also called ---

Cover-collapse sinkhole

- Unlike the other sinkholes that develop over time, this type forms suddenly

Cover-collapse sinkhole

- Most dangerous type of sinkholes