Seminar on Responsible

Mineral Resources

Development for DepEd

Science Teachers

MYTHS AND FACTS

What are Geological Hazards?

Source: Google

Why is Philippines prone to various types of mass wasting or landslide?

CLIMATICGEOLOGIC

GEOLOGICAL FACTORS

Source: DOST-PHIVOLCS

Climatic Factors

• ~ 20 tropical cyclones per year enter PAR

Numerous typhoons and extended rainy seasons/periods

Strong and shifting wave currents

Kapag may mina, may…..

Landslide?

Baha?

Sinkhole?

Lindol?

Tsunami?

PagputokngBulkan?

Bagyo?

Ano batalaga??

MYTH: Ang PAGMININA ay pangunahing sanhi ng GUHO/LANDSLIDES

FACT:

Landslide

Barangay San Jose, Antipolo City September 2012

Ang “landslide” o guho ay ang pagbaba ng lupa, bato, at putik dahil sa

“gravity” o batak ng natural na hila ng ating daigdig.

What Causes Landslide?

DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCESMINES AND GEOSCIENCE BUREAUREGIONAL OFFICE NO. XII

Driving

Force

Resisting

ForceLandslide!

Driving forces (forces that tend

to bring the block down) :

o Block’s own weight

o When wet: water pressure

Resisting forces (forces that

tend to hold the block on the

ramp) :

o Friction along base of block

and ramp

o Cohesion along base of block

and ramp

Resisting Force

Factors that Increase Driving Force

DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCESMINES AND GEOSCIENCE BUREAUREGIONAL OFFICE NO. XII

1. Gravity

2. Steep slope (Rolling to very steep terrain with >18% slope)

3. Removal of Lateral Support

4. Overloading of Slopes

5. Transitory Stresses (Vibrations caused by earthquakes and

human activities)

Factors Contributing Low Resistance Force

DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCESMINES AND GEOSCIENCE BUREAUREGIONAL OFFICE NO. XII

1. Rainfall

2. Geology of the area

3. Land Use Cover – (Poor vegetation/Barely) Soil)

Vibrations caused by earthquakes and human activities (traffic, machinery,

etc.)

o Any time plate tectonics move the soil that covers them moves with it. When

earthquakes occur on areas with steep slopes, many times the soil/unconsolidated

rock slip causing landslides.

POSIBILIDAD NG PAGGUHO KAPAG

MAY LINDOL

PAANO NAPAPABILIS NG ULAN ANG

GUHO

• Pagtaas ng pore pressure

• Pagbawas ng friction

• Pagbigat ng lupa

= REDUCED SLOPE

STABILITY.

The rain will add

weight to the soil

Pore pressure

pushes the soil

grains apart. As a

result, the friction

is decreased

CROWN

SCARP

TOE

Mga Features o Parte ng Guho

SURFACE OF RUPTURE

SLUMPED BLOCK

Illustration credit: USGS

MYTH: Ang PAGMININA ay pangunahing sanhi ng PAGBAHA/FLOODING

FACT:

Flood

Angono, Rizal September 29, 2009(JAY DIRECTO/AFP/Getty Images)

Ang flooding o pagbaha ay ang pag-apaw ng sobrang tubig sa natural nitong

daluyan (tulad ng sapa, ilog at dagat).

Major Contributing Factors to High Incidence ofFlooding

DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCESMINES AND GEOSCIENCE BUREAUREGIONAL OFFICE NO. XII

1. Rainfall

2. Slope and Topography

3. Drainage System & Watershed

4. Soil/Rock Types

5. Land Use Cover

Major Contributing Factors to High Incidence ofFlooding

DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCESMINES AND GEOSCIENCE BUREAUREGIONAL OFFICE NO. XII

Drainage Basin

Drainage System & Watershed - area of watershed and

capacity of channel ways to contain its runoff peak

discharge

MINDANAO WATERSHED AREA

DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCESMINES AND GEOSCIENCE BUREAUREGIONAL OFFICE NO. XII

Watershed - is an area of

land that drains all the

streams and rainfall to a

common outlet such as the

outflow of reservoir, mouth of

bay or any point along a

stream channel.

General Santos City

Cotabato City

Koronadal City

Tacurong City

Kidapawan City

Mindanao River Basin

Area: 21, 502 Km2

Malungon-Buayan River Basin

Area: 1,620 Km2

WATERSHEDAREA

DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCESMINES AND GEOSCIENCE BUREAUREGIONAL OFFICE NO. XII

City of Malaybalay

FACT:

MYTH: Ang PAGMININA ay pangunahing sanhi ng SINKHOLES

Subsidence due to Sinkhole

Sinkhole in Dumanjug, Cebu

Sinkhole is a depression or hole in the ground caused by

some form of collapse of the surface layer. Most are

caused by karst processes—for example, the chemicaldissolution of carbonate rocks or suffusion processes.

Silway 8, Polomolok, South Cotabato

MYTH: Ang PAGMININA ay pangunahing sanhi ng LINDOL/EARTHQUAKE

FACT:

Earthquake

Why Do Earthquakes Occur?Scientific study has shown that earthquakes can occur due to:• Sudden formation of a new fault (fracture on which sliding occurs)

• Sudden slip on an existing fault

• Sudden change in the arrangement of atoms in the minerals of a rock

• Movement of magma in a volcano

• Explosion of a volcano

• Giant landslides

• Meteorite impact

• Underground nuclear bomb tests

Where Do Earthquakes Occur?• Most earthquakes occur in narrow zones around the globe called seismic belts

• Most seismic belts correlate with plate boundaries, but not all

• Some earthquakes occur in intraplate settings (within a tectonic plate)

Earthquake Terminology• Hypocenter (Focus): actual location of the earthquake at depth

• Epicenter: location on the surface of the Earth above the hypocenter

• Hanging Wall: top block of a fault (where a light would hang from)

• Footwall: bottom block of a fault (where you would stand)

Active Faults in the Philppines

Mindanao Fault= Daguma Extension

Earthquake Size• Size of an earthquake is measured by two DIFFERENT means:

• 1) Intensity 2) Magnitude

• Mercalli Intensity Scale – defines the intensity of an earthquake by the amount of damage it does and how much shaking is felt.

• Denoted by roman numerals

Mw6.9 Loma

Prieta 1989

Earthquake Magnitude• The size of an earthquake

is also measured by its magnitude

• Based on the maximum amplitude of ground motion measured by a seismograph

• Magnitude does not depend on distance but Intensity does

• Any seismograph will record the same magnitude because it is a standardized measure

• Intensity depends on the local geologic properties

FACT:

MYTH: Ang PAGMININA ay pangunahing sanhi ng TSUNAMI

Tsunami

Tsunamis

• Not “tidal waves” – they have nothing to due with tides

• Tsunami – a large wave that is generated by an earthquake, landslide, or meteor impact

• When a fault movement causes vertical movement beneath the sea, water rushes too fill the void so, normal (rarely) or reverse (most common) faults are involved.

• Since subduction zones can produce the largest earthquakes (most slip and rupture length) they can also generate the largest tsunamis

1964 Chile Earthquake and Tsunami

• Tsunamis can travel great distances

(animation of Chile tsunami)

1976 MORO GULF EARTHQUAKE

MYTH: Ang PAGMININA ay pangunahing sanhi ng PAGPUTOK NG BULKAN/ VOLCANIC ERUPTION

FACT:

Volcanic Eruption

Volcanoes of the World and Their Tectonic Environments

Volcano Morphology• Geologists distinguish three main types of volcanoes based on their shape.

• Shield Volcano – long and broad, low angle volcanoes that form from successive eruptions of fluid basalt e.g. Mauna Loa, HI

• Stratovolcano (composite volcano) – steep-sided alternating layers of ash and lava flows, typically intermediate in composition e.g. Mt. Rainier, WA

• Cinder Cones – cone-shaped piles of tephra at the angle of repose. Typically the smallest and easiest to erode (short-lived)

• Lava Flows:• Basaltic / Mafic Lava Flows:

• low viscosity• low SiO2

• high temp

Products of Volcanic Eruptions

Pahoehoe and Aa lava flow on Mauna Loa, Hawaii

Pahoehoe: Ropey smooth wrinkly lava flowsAa: Angular blocky irregular lava flows

Products of Volcanic Eruptions

• Andesitic / Intermediate Lava Flows: • intermediate viscosity (more SiO2 than basalt)

• flows slowly

• flows <10 km long

Products of Volcanic Eruptions

• Rhyolitic / Felsic Lava Flows: • high viscosity (more SiO2 than basalt and andesite)

• low temp

• flows slowly, if at all (typically < 1 km long flows)

Felsic (Explosive) Eruptions• Felsic magmas are more viscous and typically have more

dissolved gasses, so they tend to be explosive in nature. They commonly result in:

• Ash clouds, Pyroclastic Flows (nuée ardentes), lapilli, etc…

Products of Volcanic Eruptions• Pyroclastic Debris:

• If the magma is viscous, gas may not be able to escape and it will eventually cause an explosive eruption composed of fragmented material called pyroclastic debris, which includes various components:

• Volcanic Ash: tiny (0.01 mm grains) glass shards

• Lapilli: pea to plum sized balls of volcanic ash composed of various things:• made of Scoria = Cinders

• made of molten material that becomes tear drop shaped = Pelé’s Tears

• Made of stringy molten material = Pelé’s Hair

• Made of wet ash = accretionary lapilli

• Blocks – chunks of wall rock blasted out of volcano

• Bombs – chunks of juvenile material blown out of volcano

• Tephra – any unconsolidated (loose) pyroclastic material

• Tuff – lithified ash mixed with lapilli (‘welded’ if grains are squished)

Tephra + Rain = Lahars• Lahar – a dense river of mud that happens when loose tephra mixes

with rain or groundwater. They are very dense and powerful and can destroy just about anything in their path. They can literally carry away large bridges. Can also travel 10’s of km away from an active volcano.

A Mt. St.

Helens lahar

after the 1980

eruption

Name of Volcano RAGANG

Classification Active

Current Summit Activities

No sign of any volcanic activity

Elevation (km) 2.815

Base Diameter (km) 32

Type of Volcano Stratovolcano

Number of Historical Eruptions

8

Latest Eruption/Activity

1916 July

Name of Volcano MATUTUM

Classification Active

Current Summit Activities

No sign of any volcanic activity

Elevation (km) 2.293

Base Diameter (km) 25

Type of Volcano Stratovolcano

Number of Historical Eruptions

1

Latest Eruption/Activity

07 March 1911

Name of Volcano PARKER

Classification Active

Current Summit Activities

No sign of any volcanic activity

Elevation (km) 1,784

Base Diameter (km) 40

Type of Volcano Stratovolcano

Number of Historical Eruptions

1

Latest Eruption/Activity

04 Jan. 1640

MYTH: Ang PAGMININA ay pangunahing sanhi ng BAGYO/ TYPHOON

FACT:

Typhoon

References:

• Mines and Geosciences IEC Materials

• Philippines Institute of Volcanology and Seismology (PhiVolcS)

• Philippines Atmospheric, Geophysical and Astronomical Services Administration (PAG-ASA)

• United States Geological Survey (USGS)

• National Oceanic and Atmospheric Administration (NOAA)