Download - Chapter 3 The Dynamic E arth
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Chapter 3The Dynamic Earth
It’s divided into 4 sections
The geosphere The atmosphere The hydrosphere
The biosphere
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1 )Geosphere • The earth is an integrated system that consists
of rocks ( geo ), air ( atmo ) , water ( hydro ) , living organism ( biosphere ).
• So geosphere is: the solid part of the earth that consists of rocks , soils , sediments.
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The composition of the geosphere
• The earth’s surface is divided into several layers according to the density of materials forming these layers….they are from up to down
• Earth’s crust• Mantle • Core
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Earth’s crust
mantle
core
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Earth’s crust1) It’s the outermost layer of the earth’s surface2) It’s made almost entirely of light elements3) Less than 1% of the planet’s mass4) Earth’s thinnest layer ( 5 to 8 kms thick beneath the oceans or 20 to
70 kms beneath the continents)
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mantle1) It’s the layer beneath the crust2) Made up of rocks with medium density3) Makes up up to 64 % of the earth’s mass4) Approximately 2900 kms thick
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core1) It’s the deepest layer of the earth2) Made up of rocks with high density3) Its radius is equal to 3,400 kms
Finally lets hear that song about the layers of earth
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&here’s your assignment
Draw a table classified into 3 columns fora) Crustb) Mantle c) CoreComparing between them according to what you’ve learnt
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Other scientists divided the earth into 5 layers according to the physical
properties of each layer
Lithosphere: Cool , rigid layer 15 kms to 300 kms thick Includes the crust & the upper part of the mantle Divided into huge pieces called tectonic plates
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Asthenosphere: Beneath the lithosphere Solid layer of middle mantle Flows very slowly, allowing the
tectonic plates to move over it
Mesosphere: Beneath the asthenosphere Lower part of mantle
Outer core: Dense liquid layer Due to high temperature
Inner core: Dense solid layer although to high temperature
due to high pressure
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Lets stop here today
make sure you wrote your homework See you next time
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Let’s warm up
What happens when you put some pieces of ice in a beaker containing water
Can you remember in which layer of the earth are the tectonic plates present?
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The same thing happens to the tectonic plates ( present in the lithosphere )
They slide over the underlying asthenosphere so the whole continents present in those plates move
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The sliding of the continents over the surface of these moving tectonic plates
cause most of the geological activities at the surface of earth like:
Earthquakes Volcanic eruptions erosion Mountain formation
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How can they cause those geological phenomena?
• When theses plates move they cause enormous forces at their boundaries by either:
Sliding away from each other ( divergent )Colliding with each other ( convergent )Slipping one past the other ( transform )
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How do earthquakes occur ?
• A fault is a : Break in the earth’s crust along which blocks of earth’s crust slide relative to one another.
• When rocks that are under stress suddenly break along a fault a series of ground vibrations are set off.
• They occur all of the time but many of them are so small that we can’t feel.
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How to measure the strength of the earthquake?
• By the amount of energy released from the earthquake movement ,,,the measure is called Ricktar magnitude
• Smallest magnitude is (2.0) [ can’t be felt ]• Largest magnitude is ( 9.5 ) [ destructive ]• Each increase by 1 means 31.7 times more energy
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Where do earthquakes occur?
• It occurs mainly in the boundaries between the plate tectonics because of the enormous stresses that are generated when tectonic plates separate , collide , or slip past each other
• Lets see different maps for the boundaries between plate tectonics
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The red line = boundary
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Volcanoes • What is a volcano ???• It’s a mountain built from magma
( molten rocks ) that rises from the interior of the earth.
• Where does it occur???• It occurs near the boundaries of the tectonic
plates as well as earthquakes.• Specially when they collide or separate
from each other
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Local effects of volcanic eruptions1. Human loss2. Volcanic ash can mix with water & produce
a mudflow ( in 1985 Nevado Del Ruiz in Colombia erupted melting ice at the volcanic summit, a mudflow raced downhill & engulfed the town of Armero)
3. Volcanic ash falls to ground destroy buildings ,bury crops , damage car engines
4. Ash causes breathing difficulties
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Global effects of volcanic eruptions
• It can change the climate of the whole earth for several years ( how??)
• The clouds of the volcanic ash & sulfur rich gases may reach the upper atmosphere reducing the amount of light & heat reaching the earth causing a drop of average global temp by several tenths of degree celesius
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Erosion
• Originally the rocks may be formed at the boundaries of tectonic plates
• They are subjected to either wind or running water which may cause its erosion
• Erosion is the removal & transport of the earth’s surface material
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• The more the rocks are subjected to wind or running water , the smoother these rocks will be .
• This observation helped the scientists to learn that the round-topped Appalachian mountain in the eastern United States are older than the jagged Rocky Mountains in the west
• Wind & running water cause erosion of coastlines to give variety of spectacular landforms.
• Rivers can carve deep gorges into the landscape.