When a natural event become extreme in its occurrence, it poses a danger to human life and property.
What is a natural disaster?
When the event causes significant damage to life or property.
What should a natural disaster be based upon?
A natural disaster should be defined on the basis of its human consequences, not on the phenomenon that caused it.
What is a catastrophe?
When it kills or injuries large numbers of people or causes extensive property damage.
What are Geophysical disasters?
earthquakes, tsunamis, volcanic eruptions
What about Hydrometeorological?
tornadoes, hurricanes, floods, droughts
What is Rapid, or cataclysmic?
- One large-scale event causes most of the damage and destruction. Following this event, there may be a tremendous amount of suffering and chaos, but things relatively soon begin to improve.
- Cataclysmic disasters include earthquakes, volcanic eruptions, cyclonic storms, and floods.
- The damaged area in a cataclysmic disaster is usually relatively small, however loss of life is sudden and therefore dramatic.
What about in a long-term, continuing disaster?
- In a long-term, continuing disaster, the situation after the event remains constant or may even deteriorate as time passes.
- Continuing natural disasters include droughts, deforestation, and desertification (The process by which fertile land becomes desert)
- The damaged area in a continuing disaster may be extremely large.
- While continuing disasters disrupt transportation and distribution networks, they can also bring them to a complete halt and ultimately destroy the system itself.
Explain Primary effects.
directly caused by disaster event - water damage from flood or building collapse from earthquakes shaking
Explain Secondary Effects.
short-term effects associated with but not directly caused by disaster - flooding due to landslide moving into lake, which spills out.
Explain Tertiary effects.
long-term/permanent effects from natural disaste r- uplift of land due to earthquake.
What is Statistical prediction?
average expectations based on past experience
What is Mitigation?
efforts to prepare for a disaster and reduce its damage.
Give some examples of Mitigation.
Mitigation includes: land-use and urban planning; government policy (federal, provincial, municipal); public education
What are Disaster Mitigationmeasures?
measures that eliminate or reduce the impacts and risks of hazards through proactive (creating or controlling a situation by causing something to happen rather than responding to it after) measures taken before an emergency or disaster occurs.
Measures may be structural, e.g. flood dikes (a long wall or embankment built to prevent flooding from the sea.) or non-structural (e.g. land use zoning and building codes).
What are some Pre-disaster activites?
What about Emergency Response Warning?
• Evacuation / Rescue
• Emergency Assistance (food, shelter, medical)
Give some examples of Post-disaster activities.
Transitional period - Repair Structure and lifelines
Reclaim and clear land
Reconstruction Period -
What is the Lithosphere?
Transitional period - Repair Structure and lifelines
Reclaim and clear land
Reconstruction Period -
What is the Lithosphere?
stiff and rigid outer rind (The tough outer layer of something) of the Earth
What is the Asthenosphere?
inner, hotter, easily deformed part of the Earth
What is the Mantle?
a rocky shell about 2,900km thick that constitutes about 84% of Earth's volume
What are the Tectonic plates?
large blocks of lithosphere
What is the Oceanic crust?
basalt (low-silica(SiO2)) crust, high density
What is the Continental crust?
granitic (silica-rich) crust, low density
What is the Moho (Mohorovicic Discontinuity)?
the boundary between Earth’s crust and mantle, 7 – 35 km
What is convection cell or convective flow?
The mobile rock beneath the rigid plates is believed to be moving in a circular manner somewhat like a pot of thick soup when heated to boiling. The heated soup rises to the surface, spreads and begins to cool, and then sinks back to the bottom of the pot where it is reheated and rises again. This cycle is repeated over and over
Who proposed the Continental Drift Theory?
Proposed by Alfred L. Wegener in 1912
What was the name of the Supercontinent, and when did it start to break up?
Supercontinent Pangaea started to break up about 225 - 200 million years ago
Where do most of the earthquakes and volcanoes occur?
Most of the earthquakes and volcanoes occur along or near plate boundaries.
What are Divergent boundaries?
where new crust is generated as the plates pull away from each other.
What are Convergent boundaries?
where crust is destroyed as one plate dives under another
What are Transform boundaries or transform fault-boundaries?
where crust is neither produced nor destroyed as the plates slide horizontally past each other.
What are the two types of Divergent boundaries?
1) Oceanic ridges (spreading centres) - The rate of spreading along the Mid-Atlantic Ridge is about 2.5 centimeters per year (cm/yr), or 25 km in a million years. Iceland is the best example
2) Continental Rifts - Spreading centers in the continents pull apart at much slower rates. East African Rift zone is an example of this.
What are the three types of Convergent boundaries?
1) Collision zones (Two Continental Plates) - Example - The Himalayas
2) Subduction Zones (Two Oceanic Plates) - When two oceanic plates converge, one is usually subducted under the other, and in the process a trench (a long, narrow ditch) is formed
3) Subduction Zone (Oceanic and Continental Plates) - a continental volcanic arc forms on a continent where oceanic lithosphere descends beneath the continental margin. Earthquakes are generated in this zone
What is an example of a Transform boundary?
The San Andreas fault zone (about 1,300 km long and in places tens of kilometers wide) slices through two thirds of the length of California. Along it, the Pacific Plate has been grinding horizontally past the North American Plate for 10 million years, at an average rate of about 5 cm/yr
J. Tuzo Wilson, the Canadian geophysicist, has discovered transform faults
What are Hotspots?
- the surface expressions of hot columns of molten (or partially molten) rock anchored in the deep mantle.
- the origin of hotspots in unclear
- At hotspots, plumes of hot but solid rock rising within mantle begin to melt as rock pressure on them drops.
- The volcanic Hawaiian Islands have formed in the middle of the Pacific Ocean
What is the Epicenter?
- the point on the earth's surface vertically above the hypocenter (or focus)
What are Faults?
Faults are simply fractures in the crust along which rocks on one side of the break move past those on the other.
How are faults measured?
according to the amount of displacement along the fractures
How can faults be classified as?
according to the way the rocks on either side of the fault move in relation to each other
Explain Normal faults.
They move on a steeply inclined surface, and rocks above the fault surface slip down and over the rocks beneath the fault
Explain Reverse/Thrust faults.
They move rocks on the upper side of a fault up and over those below; thrust fault is more gently inclined (an inclination angle less that 45°)
Explain Strike-slip faults.
They are vertical fractures where the blocks have moved horizontally
Explain the Elastic Rebound Theory.
Henry F. Reid (1910) concluded that the earthquake must have involved an "elastic rebound" of previously stored elastic stress
Rocks are elastic, like a spring, and can bend when a force is applied
What is Stress?
refers to the forces imposed on a rock
What is Strain?
refers to the change in shape of the rock in response to the imposed stress. The larger the stress applied, the greater the strain.
True/False The crust of the earth can gradually store elastic stress that is released suddenly during an earthquake.
True/False With increasing stress, a rock deforms elastically, then plastically, before ultimately failing or breaking in an earthquake.
Where do Strike - Slip faults occur?
Transform boundaries (San Andreas, California; Turkey)
Where do Reverse/Thrust faults occur?
Convergent boundaries (Alaska, Chile, Indonesia, Japan)
Where do Normal faults occur?
Divergent boundaries (East Africa)
What are Body waves?
travel through the interior of the Earth
How many types of body waves are there?
Primary, or Compressional waves (P) - travel the fastest (5- 6 km/sec in the continental crust).
- They cause the matter to oscillate forward and backward, parallel to the motion of the seismic wave front.
- P waves push and pull the rock that they pass through.
Secondary, or Shear waves (S) -
- slower (~3.5 km/sec in the upper crust).
- They cause matter to oscillate side-to-side, perpendicular to the motion of the wave front.
- S waves shear (cut) the rock that they pass through.
What are Seconday waves?
they travel along the Earth's surface. They are slower than body waves, and they do the damage in Earthquakes.
How many types of Secondary waves are there?
Love waves - shake the ground side-to-side like an S wave
Rayleigh waves - displace the ground like rolling ocean waves. The ground rolls forward and up and then down and backwards. This is similar to a p wave but with the extra up-down motion
What is a Seismograph?
A seismograph records the shaking of earthquake waves on a record called a seismogram.
What does the Modified Mercalli Intensity Scale measure?
It is based on how strongly people feel the shaking and the severity of the damage it causes.
Write the following levels of intensity according to the Mercalli Intensity scale from lowest intensity (didn't feel anything) to high intensity (Objects thrown into the air)
I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
What is the Earthquake magnitude?
The magnitude is a number that characterizes the relative size of an earthquake. Magnitude is based on measurement of the maximum motion recorded by a seismograph.
Explain the Richter scale.
The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology
- The Richter numerical scale reflects amount of energy released during earthquakes (magnitude) determined by amplitude (i.e., amount of ground movement) on seismogram;
- Richter scale is open-ended, however, in practice M = 9 is maximum
- The Richter Scale is not used to express damage
swarms of minor earthquakes; may warn of major earthquakes if they announce the onset of fault slippage. Foreshocks precede about 30 % of all earthquakes. The problem is that the big earthquakes mostly occur with no foreshocks
the study of prehistoric fault movements, helps us understand future fault behavior.
Explain Seismic gaps.
where movement has not occurred on a fault segment, they are likely areas for future fault movements.
Describe Liquefaction. (the conversion of a solid or a gas into a liquid, the process of liquefying)
a process by which water-saturated sediment temporarily loses strength and acts as a fluid, like when you wiggle your toes in the wet sand near the water at the beach.
What are some of the ways that may reduce the Earthquake damage? (How can it be mitigated?)
Earthquake damage can be mitigated through building codes,retrofitting (Add (a component or accessory) to something that did not have it when manufactured.), and land - use planning, as well as educating the public about earthquake preparedness
Define Tsunami (Japanese term)
roaring and resounding (emphatic or echoing sound) sea
How are tsunamis usually generated?
Tsunamis are most commonly generated by earthquakes, but they can also be caused by volcanic eruptions, landslides or rockfalls, volcano flank collapses, and asteroid impacts.
Which type of faults do earthquake-generated tsunami occur most commonly on?
Earthquake-generated tsunami occur most commonly on a reverse/thrust - fault movement (subduction zone)
A catastrophic tsunami, many times larger than any in the historical record is likely to come from?
the flank collapse of an oceanic volcano
A wave can be described by its: wavelength
describe each of these terms.
wavelength - horizontal distance between successive crests or troughs
height - vertical distance between any crest and succeeding trough
period - time interval between the passage of successive crests (time between waves)
Define Tsunami run-up.
the height the water reaches when it sweeps up on shore.
Tsunami reach shore as a series of waves, often tens of minutes apart, and may continue for hours.
The third and subsequent waves are often the largest.
Name the historical tsunami.
Indian Ocean (Sumatra, Indonesia) tsunami, 12/26/2004 More than 230000 died
What should the inhabitants near the coastline do when they hear of a tsunami danger?
inhabitants should run upslope (several tens of meters above sea level) or drive directly inland (a kilometer or more inland)
What is Vulcan (latin Vulcanus)?
in Roman religion, the god of fire and the forge (the blacksmith's workshop, a smithy)
Define a volcano.
A hill or mountain formed at a vent from which molten rock, or magma, and gases reach the Earth’s surface and erupt
Once the magma reaches the surface, this is called LAVA
What are Magma chambers?
large masses of molten magma
A hot rock deep within the Earth may melt by..... (3 ways)
increased temperature, decreased pressure, or addition of water
How can one define the violence of a volcano? (3 ways)
• viscosity (how fluid the magma is)
• volatiles (the quantity of water vapor and other volcanic gases it contains)
• volume (the type and amount of magma)
The viscosity of a magma is largely controlled by the silica content:
high - silica magmas (granite, rhyolite, 70% of SiO₂) have high viscosity; they are thick and pasty
low- silica magmas (basalt, 50 % of SiO₂) have low viscosity; they are fluid
The volatiles of a volcano:
Magmas that contain little water erupt quietly as lavas; those that contain large amounts of water are likely to explode
A volcanic eruption is more explosive for magmas with higher viscosity and larger quantities of volatiles
Where are most hazardous volcanoes located?
Most hazardous volcanoes are near subduction zones (Pacific “Ring of Fire”)
Depending on its style of eruption, a volcano can produce: (3 types)
(air-fall ash and pyroclastic flow deposits)
lahars ( volcanic mud flows)
Non-explosive Eruptions: Lava Flow
Basaltic magma commonly produces non-explosive eruptions, spilling out in the form of lava
What are the types of lava?
Types of lava include:
ropy pahoehoe (Having a thick, sticky consistency between solid and liquid; having a high viscosity.)
rubbly aa -
Explosive eruptions produce pyroclastic material, solidified magma in the form of ash.
When Hot ash combines with rain or melting snow, producing a lahar, or mudflow
What does the size of an explosive eruption depend on? (3 things)
• the amount of magma
• the magma viscosity
• magma water- vapor content
What about The Volcanic Explosivity Index (VEI)
The VEI quantifies eruption size, volume, and violence
Explain Shield volcanoes.
• fluid basaltic lava
• low viscosity
• low volatile content, broad and gently sloping sides
• large volumes
• Hotspots ; Mid-oceanic volcanic islands
Explain Cinder cones
• basaltic lava
• small size
• low viscosity
• steep sides
• moderate volatile content
• erupt over only one short period (a few months to a few years)
• Hotspots, subduction zones, and continental rift zones
EXAMPLE : Cerro Negro, Nicaragua (the most active cinder cone volcano)
• the classic volcano, cone-shaped
• moderate viscosity
• moderate slope
• moderate to high volatile content
• consist of layers of lava, fragmental debris, and ash
Explain Composite volcano:
• andesitic lava
• the most violent volcanoes
• location - subduction zone
Explain Lava Domes
• rhyolitic lava (very acid volcano rock)
• small- to- moderate size
• high magma viscosity
• steep flanks
• low- to- moderate volatile content
• Location: subduction zones
• Like toothpaste squeezed from a giant tube, viscous lava piles up around a vent to form a lava dome
Explain Continental Calderas
• rhyolite volcanoes
• high viscosity
• high volatile content
• gently sloping flanks
• Location: continental hotspots, continental rift zones
• calderas are formed when the roof over a giant magma chamber collapses
• Their infrequent eruptions are extremely destructive
What are a mixture of hot ash and gas called?
Shield volcanoes are characterized by....
gentlysloping sides and are typically segmented by eruptive rifts.
have the classic volcano shapeand moderate to high volatile content.
Cinder cones are characterized by...
their small size and steep sides. Erupting cinder cones produce glowing fragments of cinders that rarely cause serious injury.
As a lava dome rises and expands...
lava fragments tumble down its sides while molten lava continues to rise within the dome. If the dome collapses, it may release a pyroclastic flow that can be extremely dangerous.
Continental calderas are formed when...
the roof over a giant magma chamber collapses. Their infrequent eruptions produce huge volumes of pyroclastic material and are extremely destructive
Millions of people live in risk of a volcanic hazard, (3 risks)
a) rich, fertile soil for agriculture
b) beautiful vistas (a pleasing view)
c) climate appeals to retirees (Hawaii; Italy)
Lava flows are....
destructive to property, becauset hey ignite and overwhelm everything in their path.
They do not pose a significant threat to human lives because they are slow moving.
read lecture 11 VERY carefully memorize everything....