Week3+4 Cont . Chapt 1 : Natural Environmental Hazards

Dr. Mohammed Ajjour University Of Palestine

2009,

Cont, environ. natural hazards.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

University Of Palestine 2009, Dr. Mohammed Ajjour

Cause of physical damage and loss of human lives in coastal areas and river banks as well as in low areas after heavy rainfall.

Causes Heavy rainfall Coastal flooding due to sea storms Dam failures. Effects Primary (death, destroy buildings

etc.) Secondary and tertiary (diseases,

electricity and water, collapse of transportation system

The Floods

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

- Due to collision between cold 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.

University Of Palestine 2009, Dr. Mohammed Ajjour

Tornadoes and Storms

Typhoons and hurricanes

In Atlantic and USA called Hurricane,

in Pacific and SE Asia called Typhoon. Tropical low pressure Circular with

diameter reach 600 km; and very strong winds

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.

University Of Palestine 2009, Dr. Mohammed Ajjour

Tsunami(s), are a series of waves generated by large, violent earthquakes occurring near the ocean. Not all earthquakes generate tsunamis . By far, the most destructive tsunamis are generated from large shallow earthquakes . destructive tsunami waves can travel across an ocean spreading destruction across their path. Similar displacements of the ocean floor can also be produced by volcanic eruptions and submarine landslides.

As the tsunami enters the shoaling water near the coast, its velocity decreases and its height increases. It is in these shallow waters that tsunamis become a threat to life and property, for they can crest to heights of more than 30-50 meters and strike with devastating force.

University Of Palestine 2009, Dr. Mohammed Ajjour

Tsunami(s)

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.

University Of Palestine 2009, Dr. Mohammed Ajjour

Cont.Desertification

Dry climate is a major 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.

University Of Palestine 2009, Dr. Mohammed Ajjour

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.

University Of Palestine 2009, Dr. Mohammed Ajjour

Cont.Desertification

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

cultivation• Reduced erosion and soil

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

environmente

University Of Palestine 2009, Dr. Mohammed Ajjour

Cont.Desertification