environmental sciences course earth sciences dr.-eng. hasan hamouda

Environmental Sciences Course

Earth Sciences

Dr.-Eng. Hasan Hamouda

University Of Palestine International ENVI005 Dr.-Eng. Hasan Hamouda

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Contents

The formation of the Earth Gravitational Attraction The structure of the Earth micro plates Rocks, minerals, and geologic

structures Solar Radiation


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Formation of the Earth

-Among the nine planets in the solar system, Earth is the only one which is known to support life.

-All the materials we use are taken from the Earth and it supplies us with everything we eat and drink.

-It receives energy from the Sun, which drives its climates and biological systems.


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-The oldest rocks, found on the Moon, are about 4.6 billion years old and this is generally accepted to be the approximate age of the Earth and the solar system

generally .

-There are several rival theories describing the process by which the solar system may have formed .


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-The most widely accepted theory, first proposed in 1644 by René Descartes, proposes that the system formed from the condensation of a cloud of gas and dust, called the ‘primitive solar nebula’ (PSN).

-It is now thought this cloud may have been perturbed by material from a supernova explosion. Fusion processes within stars convert hydrogen to helium, In larger stars go on to form all the heavier elements up to iron.


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Elements heavier than iron can be produced only under the extreme conditions of the supernova explosion of a very massive star, and the presence of such elements (including zinc, gold, mercury, and uranium) on Earth indicates a supernova source.



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-As the cloud condensed, its mass was greatest near the centre. This concentration of matter comprised the Sun, the planets forming from the remaining material in a disc surrounding the star, and the whole system rotated.

-The inner planets formed by accretion. Small particles moved close to one another, were drawn together by their mutual gravitational attraction, and as their masses increased they gathered more particles and continued to grow



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-At some point it is believed that a collision between the proto-Earth and a very large body disrupted the planet, the material re forming as two bodies rather than one: the Earth-Moon-system.

-This explains why the Earth and Moon are considered to be of the same age and, therefore, why lunar rocks 4.6 billion years old are held to be of about the age of the Earth and Moon.



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The structure of the Earth

As it exists today, the Earth has :a mean radius of 6371 km Equatorial circumference of 40077 kmPolar circumference of 40009 km Total mass of 5976× 1018ton mean density of 5.517 g. cm-3 Land 149× 106 km2 (29 %) Glaciers ice sheets 15.6× 106 km2 (3%)Oceans and seas 361× 106 km2 (69%)


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-At its centre, the Earth has a solid inner core, 1370 km in radius, made from iron with some nickel .

-This is surrounded by an outer core, about 2000 km thick, also of iron with nickel, but liquid, although of very high density .

-Movement in the outer core acts like a self- exciting dynamo and generates the Earth’s magnetic field.



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-Outside the outer core, the mantle, made from dense but somewhat plastic rock, is about 2900 km thick

- at the surface there is a thin crust of solid rock, about 6 km thick beneath the oceans and 35 km thick (but less dense) beneath the continents.



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On Earth, but possibly on no other solar-system planet, the crust consists of blocks, called ‘plates’, which move in relation to one another. The theory describing the process is known as ‘plate tectonics’ (GRAHAM, 1981).

At present there are seven large plates, a number of smaller ones, and a still larger number of ‘micro plates’. The boundaries (called ‘margins’) between plates can be constructive, destructive, or conservative.

micro plates


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constructive margins

two plates are moving apart and new material emerges from the mantle and cools as crustal rock to fill the gap, marked by a ridge. There are ridges near the centers of all the world’s oceans.

destructive margin

Where plates move towards one another there is a destructive margin, marked by a trench where one plate sinks (is sub ducted) beneath the other.

micro plates


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conservative margins

At conservative margins two plates move past one another in opposite directions.

There are also collision zones, where continents or island arcs have collided. In these, all the oceanic crust is believed to have been sub ducted into the mantle, leaving only continental crust. Such zones may be marked in various ways, one of which is the presence of mountains made from folded crustal rocks.

micro plates


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An island arc is a series of volcanoes lying on the side of an ocean trench nearest to a continent. The volcanoes are due to the subduction of material.

Slowly but constantly the movement of plates redistributes the continents carried on them .

micro plates


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Rocks, minerals, andgeologic structures

-Rock that forms from the cooling and crystallization of molten magma is called

‘igneous’, from the Latin igneous, ‘of fire ,’

-All rock is either igneous or derived from igneous rock. This must be so, since the molten material in the mantle is the only

source for entirely new surface rock .


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-If the magma reached the surface before cooling the rock is known as ‘extrusive’; if it cooled beneath the surface surrounded by older rock into which it had been forced, it is said to be ‘intrusive’. - Intrusive rock may be exposed later as a result of weathering. It is not only igneous rocks that can form intrusions. Rock salt (NaCl) can accumulate in large amounts beneath much denser rocks and rise through them very slowly to form a salt dome. Salt domes are deliberately sought by geologists prospecting for oil but occasionally they can break through the surface.


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-The character of the rock depends first on its chemical composition .

-If it is rich in compounds of iron and magnesium it will be dark (melanocratic) ;

-If it is rich in silica, as quartz and feldspars, it will be light in colour (leucocratic) .

-Rock between the two extremes is called ‘mesocratic .’

-The rock comprises minerals, each with a particular chemical composition, and minerals crystallize as they cool .


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-Sandstones are perhaps the most familiar sedimentary rocks, consisting mainly of sand grains, made from quartz (silica, SiO ) which crystallized originally into igneous rock.

-Clay particles, much smaller than sand grains, can pack together to make mudstones .



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Sediments rich in calcium carbonate, often consisting mainly of the remains of shells and containing many fossils, form limestone and dolomite (sometimes known as ‘dolostone’ to distinguish it from the mineral called dolomite).



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1 .Lithosphere:

-Composed of fractured rocks; -Thickness 100-120km;

-Composed of continental plates in continuous motion resulting:

-Continents, ocean bottoms and mountains -Earthquakes and volcanoes

2. Asthenosphere

(it is part of the of the mantle)



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3 .Pedosphere

-Located above the lithosphere, -Thin strata of crashed rocks after

weathering and erosion processes of crust; -Very important for plants; Rich of organic

materials; Include air and water; -Type of soil depend on the rock origin,

weather and climate, topography, etc.


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4 .Hydrosphere

All water types covering earth surface (oceans, seas, rivers, lakes, iceglacies, etc.)GroundwaterWater depth in rivers and lakes not exceeds tenths of meters where it reaches kilometers in seas and oceans.Water covers about 71% of earth concentrated in the southern half of Earth;Water in ocean is considered saltwater (35000 mg/l TDS)


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5 .Biosphere

Includes life classes in water, lithosphere, pedosphere and air;

Life classes about 4.5 million type, most of them depends on photosynthesis process which depends on sunshine;

99% of the biosphere is composed of oxygen, hydrogen, carbon and nitrogen.



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6 .Atmosphere -Starts from some meters below the earth

surface to reach hundreds of kilometres above the surface;

-Composed of 78% Nitrogen, 21% oxygen, 0.9% Argon, 0,03% Carbon dioxide, and Neon and Helium gases;

-Divided in many stratas and the most important one is troposphere;

-Most of air mass is concentrated in troposphere ;


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Atmosphere (Radiation)

-The Sun radiates in all directions and the Earth, being a very small target at a distance of 150 million km, intercepts 0.0005 per cent of the total.

-At the top of the Earth’s atmosphere this amounts to about 1360 W m-2 , a value known as the ‘solar constant.’


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Atmosphere (Radiation)

-Solar output is not as constant as this name suggests. Between 1981 and 1984, it decreased by 0.07 per cent This is a small deviation, but a decrease of about 0.1 per cent sustained over a decade would be sufficient to produce major climatic effects and a 5 per cent decrease might trigger a major glaciations.

-Cyclical variations in the Earth’s rotation and orbit also alter the solar constant.


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Solar Radiation

-Rather less than half of the solar radiation reaching the top of the atmosphere

penetrates all the way to the surface .

-most of the ‘lost’ incoming radiation is reflected directly back into space, and about 10 per cent is absorbed or scattered by ozone, water vapor, and particulate matter in the troposphere (the sky its

color) .


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Solar Radiation

The proportion of light reflected by a surface is called the ‘reflection coefficient’, or more usually ‘albedo’ of that surface. It can be measured and is usually expressed as a fraction or a percentage, albedo varies widely from one surface to another.

environmental sciences course earth sciences dr.-eng. hasan hamouda

Documents

hasan hamoudaformation

solar system

earth micro plates rocks

hasan hamoudathe structure

hasan hamoudaelements

supernova explosion

lunar rocks

supernova source