Week3+4 Natural Environmental Hazards- Part 2 Dr. Mohammed Ajjour University Of Palestine 2009,

Week3+4 Natural Environmental Hazards- Part 2

Dr. Mohammed Ajjour University Of Palestine

2009,

Volcanoes Very damaging phenomenon to people living in close vicinity to

eruption area. At present about 1000 volcanoes are active, especially in South East

Asia and USA Most volcanoes area are connected to boundaries of colliding plates

(like in Pacific)or in situations when plates move apart under Oceans. About 80% of earth’s surface, the seafloor as well as the land,

began as molten rock that rose from deep inside the earth. Can be beneficial as sources of fertile new soil, chemicals,

geothermal Energy and minerals.

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University Of Palestine 2009, Dr. Mohammed Ajjour

A Volcano is an outlet on ground surface for melting rocks , gases , water and heat emerging from the asthenosphere .

These compounds , the Magma , are first

contained in Magma Chamber before it is released.

Lava describes the melted liquid part of rocks which lost all his gaseous components.

Con. The Volcanoes 35

00 Million years ago some simple species of Bacteria were found, which are able to exist in absence of O2 and to photosynthesise CO2 to produce free oxygen. Some of these are still there.

Since the last 550 million years, the concentration of free O2 increased to present level allowing the existence of other species presence of Oxygen. At present ,these Species are undergoing different changes and adaptations..

During this long history ,the geological processes produced the minerals ( like Gold, diamond, phosphate, Iron...etc)and Fossile Energy Sources ( Oil, Coal, gas ).

Con. The Volcanoes Hazards and impacts :(primary) Lava flow. Pyroclastic activity Emissions of poisonous Gases.

Hazards and impacts :(secondary & tertiary )

Flow of volcanic Mud Floods Tsunamis and Earthquakes Atmospheric effects ( temperature, ..). Famines and diseases


Flood A flood is a temporary covering by water of land not

normally covered by water. It occurs when the volume of water exceeds the capacity of a lake or other body of water as a result of seasonal changes in precipitation and snow melt and the escapes of water endanger land areas used by man like a village, city or other inhabited area.

Floods can also occur in rivers, when flow exceeds the capacity of the river channel, Floods often cause damage to homes and businesses if they are placed in natural flood plains of rivers.

That humans continue to inhabit areas threatened by flood damage is evidence that the perceived value of living near the water exceeds the cost of repeated periodic flooding.


Causes Heavy rainfall Coastal flooding due to sea

storms Dam failures. Effects Primary (death, destroy buildings

etc.) Secondary and tertiary (diseases,

electricity and water shortage , collapse of transportation system and shortage in food supply.

The Floods

Floods Floods control :

In many countries across the world, rivers prone to floods are often carefully managed. Defenses such as levees ,and reservoirs are used to prevent rivers from bursting their banks. When these defenses fail, emergency measures such as sandbags or portable inflatable tubes are used. Coastal flooding has been addressed in Europe and the Americas with coastal defenses, such as sea walls, and barrier islands .


.Tornados : Helical conical storms with very low central pressure causing great damage

- It develops due to collision between cold-dry air mass and warm-humid air mass below it.

- Very low central pressure

- Local effect, (cone radius few meters -10 km )

- Short duration

- Very strong (wind speed sometimes >450km/hr)

- Famous in middle and southeast USA.


Tornadoes and Storms

Typhoons and hurricanes The terms "hurricane" and "typhoon" are regionally

specific names for a strong "tropical cyclone". A tropical cyclone is the pressure system over tropical or sub-tropical waters with organized thunderstorm activity and definite cyclonic surface wind circulation .

In Atlantic and USA called Hurricane, in Pacific and SE Asia called Typhoon.

Circular low pressure area with diameter reach 600 km; and very strong winds (winds equal or exceed 33 m/s )

Duration many weeks; Wind speed >300 km/hr; When it reaches the coast it forms very high and

strong sea waves reaches 7 m height.


Typhoons and hurricanes How do tropical cyclones form ? Warm ocean water ( 26C )throughout a sufficient

depth of at least 50 m . Warm waters are necessary to fuel the heat engine of the cyclone.

An atmosphere which cools fast enough with height to allow the heat stored in the ocean waters to be liberated .

Relatively moist layers near the mid-troposphere (5 km ). Dry mid levels are not conducive

A minimum distance of at least 500 km from the equator.

A pre-existing near-surface disturbance with sufficient vorticity and convergence.


Desertification This phenomenon is presented in the form of the expansion

of desert in new areas due to environmental, climatic and human effects.

Desertification is the partial or total loss of one or more elements of the terrestrial environmental systems leading to a deterioration of their quality and productivity to a degree that these systems are not anymore able to sustain living organisms living on it.

Such systems are characterized by thin plant cover, dry underdeveloped soil and scarcity of water . Arabic countries are good example.


Cont.Desertification

Dry climate is a major ( not the single ) natural cause of desertification . Low rain fall ,high temperatures during many Months of the year, dry winds and high evapotranspiration rates create dry sensitive ecosystems.

Erosion is a worldwide problem that causes major environmental damage, including lost agricultural productivity and polluted waterways, and costs billions of dollars per year.


Human actions may increase this phenomenon such as : .

Misuse of natural plant cover : Intensive grazing ; deforesting of forest; cutting and burning trees and herbs; collecting fruits, seeds and wild flowers;. Import of new plant diseases ..etc.

Bad agricultural practices leading to soil deterioration.: intensive farming, ploughing of marginal soils , ....etc.



Competing of Desertification through:• Regional actions• Increased plant covering and

cultivation• Reduced erosion and soil

deterioration.• Well planned land use .• Urbanization policy that considers

environment.



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Week3+4 Natural Environmental Hazards- Part 2 Dr. Mohammed Ajjour University Of Palestine 2009,