Download 3.Lec3_Environmental geology and earth I

Environmental Sciences Course
Environmental geology and
earth
Dr.-Eng. Hasan Hamouda
Eng. Osama Othman
The formation of the Earth
 The structure of the Earth
 micro plates
 Rocks, minerals, and geologic
structures
 Solar Radiation

University Of Palestine UNI
3316 Dr. Hasan Hamouda Eng. Osama Othman
2
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.
University Of Palestine UNI
3316 Dr. Hasan Hamouda Eng. Osama Othman
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Formation of the Earth
- 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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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Formation of the Earth
- 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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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Formation of the Earth
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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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Formation of the Earth
- 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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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Formation of the Earth
- 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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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As it exists today, the Earth has:
a mean radius of 6371 km
Equatorial circumference of 40077 km
Polar 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%)
University Of Palestine UNI
3316 Dr. Hasan Hamouda Eng. Osama Othman
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The structure of the Earth
University Of Palestine UNI 3316 Dr.
Hasan Hamouda - Eng. Osama Othman
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The structure of the Earth
- 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 selfexciting dynamo and generates the Earth’s
magnetic field.
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Hasan Hamouda - Eng. Osama Othman
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The structure of the Earth
- 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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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micro plates
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.
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3316 Dr. Hasan Hamouda Eng. Osama Othman
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micro plates
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.
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3316 Dr. Hasan Hamouda Eng. Osama Othman
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micro plates
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.
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3316 Dr. Hasan Hamouda Eng. Osama Othman
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micro plates
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.
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3316 Dr. Hasan Hamouda Eng. Osama Othman
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Igneous Rocks
- 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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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Rocks, minerals, and
geologic structures
Sedimentation Rocks
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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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Rocks, minerals, and
geologic structures
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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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Rocks, minerals, and
geologic structures
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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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Rocks, minerals, and
geologic structures
4. Hydrosphere
All water types covering earth surface (oceans,
seas, rivers, lakes, iceglacies, etc.)
Groundwater
Water 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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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Rocks, minerals, and
geologic structures
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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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Rocks, minerals, and
geologic structures
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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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- 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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3316 Dr. Hasan Hamouda Eng. Osama Othman
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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.
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3316 Dr. Hasan Hamouda Eng. Osama Othman
30