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Page 1: Chapter 3 The Dynamic  E arth

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.