Earth Sci

When a natural event become extreme in its occurrence, it poses a danger to human life and property.

When the event causes significant damage to life or property.

A natural disaster should be defined on the basis of its human consequences, not on the phenomenon that caused it.

When it kills or injuries large numbers of people or causes extensive property damage.

earthquakes, tsunamis, volcanic eruptions

tornadoes, hurricanes, floods, droughts

- 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.

- 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.

directly caused by disaster event - water damage from flood or building collapse from earthquakes shaking

short-term effects associated with but not directly caused by disaster - flooding due to landslide moving into lake, which spills out.

long-term/permanent effects from natural disaste r- uplift of land due to earthquake.

average expectations based on past experience

efforts to prepare for a disaster and reduce its damage.

Mitigation includes: land-use and urban planning; government policy (federal, provincial, municipal); public education

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).

• Disaster Mitigation
• Disaster Preparedness

• • Evacuation / Rescue
• • Emergency Assistance (food, shelter, medical)

•  Transitional period -
• Repair Structure and lifelines
• Reclaim and clear land
• Resume service
•  Reconstruction Period -
• Replace buildings
• Restore services
• Revitalize economy

•  Transitional period -
• Repair Structure and lifelines
• Reclaim and clear land
• Resume service
•  Reconstruction Period -
• Replace buildings
• Restore services
• Revitalize economy

stiff and rigid outer rind (The tough outer layer of something) of the Earth

inner, hotter, easily deformed part of the Earth

a rocky shell about 2,900 km thick that constitutes about 84% of Earth's volume

large blocks of lithosphere

basalt (low-silica (SiO₂)) crust, high density

granitic (silica-rich) crust, low density

the boundary between Earth’s crust and mantle, 7 – 35 km

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

Proposed by Alfred L. Wegener in 1912

Supercontinent Pangaea started to break up about 225 - 200 million years ago

Most of the earthquakes and volcanoes occur along or near plate boundaries.

where new crust is generated as the plates pull away from each other.

where crust is destroyed as one plate dives under another

where crust is neither produced nor destroyed as the plates slide horizontally past each other.

• 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.

• 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

• 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

•  - 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

 - the point on the earth's surface vertically above the hypocenter (or focus)

Faults are simply fractures in the crust along which rocks on one side of the break move past those on the other.

according to the amount of displacement along the fractures

according to the way the rocks on either side of the fault move in relation to each other

They move on a steeply inclined surface, and rocks above the fault surface slip down and over the rocks beneath the fault

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°)

They are vertical fractures where the blocks have moved horizontally

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

refers to the forces imposed on a rock

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

TRUE

Transform boundaries (San Andreas, California; Turkey)

Convergent boundaries (Alaska, Chile, Indonesia, Japan)

Divergent boundaries (East Africa)

• travel through the interior of the Earth
• 

• 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.

• they travel along the Earth's surface. They are slower than body waves, and they do the damage in Earthquakes.
• 

• 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

A seismograph records the shaking of earthquake waves on a record called a seismogram.

It is based on how strongly people feel the shaking and the severity of the damage it causes.

• I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII
• 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12

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.

• 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.

where movement has not occurred on a fault segment, they are likely areas for future fault movements.

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.

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

harbour wave

high wave

roaring and resounding (emphatic or echoing sound) sea

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.

Earthquake-generated tsunami occur most commonly on a reverse/thrust - fault movement (subduction zone)

the flank collapse of an oceanic volcano

• 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)

the height the water reaches when it sweeps up on shore.

TRUE

TRUE

Indian Ocean (Sumatra, Indonesia) tsunami, 12/26/2004 More than 230000 died

inhabitants should run upslope (several tens of meters above sea level) or drive directly inland (a kilometer or more inland)

in Roman religion, the god of fire and the forge (the blacksmith's workshop, a smithy)

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

large masses of molten magma

increased temperature, decreased pressure, or addition of water

• • 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)

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

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

Most hazardous volcanoes are near subduction zones (Pacific “Ring of Fire”)

• lava
• pyroclastic materials (air-fall ash and pyroclastic flow deposits)
• lahars ( volcanic mud flows)

True

Types of lava include:

ropy pahoehoe (Having a thick, sticky consistency between solid and liquid; having a high viscosity.)

• rubbly aa -

True

When Hot ash combines with rain or melting snow, producing a lahar, or mudflow

• • the amount of magma
• • the magma viscosity
• • magma water- vapor content

The VEI quantifies eruption size, volume, and violence

• • fluid basaltic lava
• • low viscosity
• • low volatile content, broad and gently sloping sides
• • large volumes
• • Hotspots ; Mid-oceanic volcanic islands

• • 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

• • andesitic lava
• • the most violent volcanoes
• • location - subduction zone

• • 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

• • 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

pyroclastic flows

gentlysloping sides and are typically segmented by eruptive rifts.

have the classic volcano shapeand moderate to high volatile content.

their small size and steep sides. Erupting cinder cones produce glowing fragments of cinders that rarely cause serious injury.

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.

the roof over a giant magma chamber collapses. Their infrequent eruptions produce huge volumes of pyroclastic material and are extremely destructive

• a) rich, fertile soil for agriculture
• b) beautiful vistas (a pleasing view)
• c) climate appeals to retirees (Hawaii; Italy)

• 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.

okay isa 100 !!!!