MYTHS AND FACTS - region12.mgb.gov.phregion12.mgb.gov.ph/attachments/article/200/Myths and...
Transcript of MYTHS AND FACTS - region12.mgb.gov.phregion12.mgb.gov.ph/attachments/article/200/Myths and...
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Seminar on Responsible
Mineral Resources
Development for DepEd
Science Teachers
MYTHS AND FACTS
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What are Geological Hazards?
Source: Google
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Why is Philippines prone to various types of mass wasting or landslide?
CLIMATICGEOLOGIC
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GEOLOGICAL FACTORS
Source: DOST-PHIVOLCS
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Climatic Factors
• ~ 20 tropical cyclones per year enter PAR
Numerous typhoons and extended rainy seasons/periods
Strong and shifting wave currents
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Kapag may mina, may…..
Landslide?
Baha?
Sinkhole?
Lindol?
Tsunami?
PagputokngBulkan?
Bagyo?
Ano batalaga??
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MYTH: Ang PAGMININA ay pangunahing sanhi ng GUHO/LANDSLIDES
FACT:
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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.
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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
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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)
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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)
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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
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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
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CROWN
SCARP
TOE
Mga Features o Parte ng Guho
SURFACE OF RUPTURE
SLUMPED BLOCK
Illustration credit: USGS
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MYTH: Ang PAGMININA ay pangunahing sanhi ng PAGBAHA/FLOODING
FACT:
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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).
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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
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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
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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
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WATERSHEDAREA
DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCESMINES AND GEOSCIENCE BUREAUREGIONAL OFFICE NO. XII
City of Malaybalay
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FACT:
MYTH: Ang PAGMININA ay pangunahing sanhi ng SINKHOLES
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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.
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Silway 8, Polomolok, South Cotabato
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MYTH: Ang PAGMININA ay pangunahing sanhi ng LINDOL/EARTHQUAKE
FACT:
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Earthquake
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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
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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)
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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)
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Active Faults in the Philppines
Mindanao Fault= Daguma Extension
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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
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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
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FACT:
MYTH: Ang PAGMININA ay pangunahing sanhi ng TSUNAMI
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Tsunami
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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
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1964 Chile Earthquake and Tsunami
• Tsunamis can travel great distances
(animation of Chile tsunami)
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1976 MORO GULF EARTHQUAKE
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MYTH: Ang PAGMININA ay pangunahing sanhi ng PAGPUTOK NG BULKAN/ VOLCANIC ERUPTION
FACT:
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Volcanic Eruption
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Volcanoes of the World and Their Tectonic Environments
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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)
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• Lava Flows:• Basaltic / Mafic Lava Flows:
• low viscosity• low SiO2
• high temp
Products of Volcanic Eruptions
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Pahoehoe and Aa lava flow on Mauna Loa, Hawaii
Pahoehoe: Ropey smooth wrinkly lava flowsAa: Angular blocky irregular lava flows
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Products of Volcanic Eruptions
• Andesitic / Intermediate Lava Flows: • intermediate viscosity (more SiO2 than basalt)
• flows slowly
• flows <10 km long
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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)
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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…
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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)
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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
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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
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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
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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
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MYTH: Ang PAGMININA ay pangunahing sanhi ng BAGYO/ TYPHOON
FACT:
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Typhoon
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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)