Post on 19-Dec-2014
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Earth Movements 24th January 2014
The Earth’s Structure
The Earth consists of four concentric layers: inner core, outer core, mantle and crust.
The crust is made up of tectonic plates, which are constantly moving.
Earthquakes and volcanoes happen at plate boundaries.
The diagram shows the structure of the earth. In geography, taking a slice through a structure to see inside is called a cross section
The Earth is made up of four distinct layers
The inner core is in the centre and is the hottest part of the Earth. It is solid and made up of iron and nickel with temperatures of up to 5,500°C.With its immense heat energy, the inner core is like the engine room of the Earth.
The Earth is made up of four distinct layers
The outer core is the layer surrounding the inner core. It is a liquid layer, also made up of iron and nickel.It is still extremely hot, with temperatures similar to the inner core.
The Earth is made up of four distinct layers
The mantle is the widest section of the Earth. It has a thickness of approximately 3000 km. The mantle is made up of semi-molten/semi liquid rock called magma which is ≈2000⁰C. In the upper parts of the mantle the rock is hard, but lower down the rock is soft and beginning to melt.
The Earth is made up of four distinct layers
The crust is the outer layer of the earth. It is a thin layer between (6 - 90 km thick.) The crust is the solid rock layer upon which we live. There are two different types of crust: continental crust, which carries land, and oceanic crust, which carries water.
Homework for next week S1-S2 Textbook
Read page 72-73
Page 74 Question 1, 3,4 and 5
Homework for next week S1-S2 Textbook
Read page 76 - 77
“To take you further” Question 1 – 6
Notes from Journey to the centre of the planet
There are two different types of crust
continental crust, which carries land.
oceanic crust, which carries water and the seabed.
Page 76
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Plate tectonics
Plate tectonicsThe Earth's crust and upper part of the mantle are broken into large pieces called tectonic plates. There are 7 large plates and 12 smaller plates covering the earth.
These are constantly moving at a few centimetres each year.
Although this doesn't sound like very much, over millions of years the movement allows whole continents to shift thousands of kilometres apart. This process is called continental drift.
Convection currents• The plates move because of
convection currents in the Earth's mantle. These are driven by the heat produced by the inner and outer core.
• Where tectonic plates meet, the Earth's crust becomes unstable as the plates push against each other, or ride under or over each other.
• Earthquakes and volcanic eruptions happen at the boundaries between plates, and the crust may ‘crumple’ to form mountain ranges.
Evidence for plate tectonics
The match in shape between the east coast of South America and the west coast of Africa suggests both were once part of a single continent. There are similar patterns of rocks and similar fossils on both sides of the Atlantic - including the fossil remains of land animals that would have been unable to swim across an ocean. Page 4
Evidence for plate tectonics
Plate tectonics explained why earthquakes and volcanoes were concentrated in specific places - around the boundaries of moving plates.
Different Types of Plate Boundaries
• The movement of the plates, and the activity inside the Earth, is called plate tectonics.
• Plate tectonics cause earthquakes and volcanoes. The point where two plates meet is called a plate boundary.
• Earthquakes and volcanoes are most likely to occur either on or near plate boundaries.
Different Types of Plate Boundaries
Key: _________ = major plate boundary, = direction of the movement = Major earthquake and volcano zones
Parting Plates / Constructive Plate Boundary
Constructive boundaries tend to be found under the sea, e.g. the Mid Atlantic Ridge.
MagmaConvection current
Eurasian plateNorth American plate
Under sea Volcano new land
Surtsey island, Iceland.
When the magma reaches the surface, it cools and solidifies to form a new crust of igneous rock.
This usually involves a continental plate and an oceanic plate
Colliding Plates / Destructive Plate Boundary
Mantle
Oceanic CrustNazca Plate
Continental CrustSouth American Plate
Pacific ocean
Volcanic eruption “boom!”
Point of friction – oceanic plate melts
This usually involves a continental plate and an oceanic plate
Different types of volcano
• still active and erupt frequently• dormant (temporarily inactive but not fully
extinct)• extinct (never likely to erupt again)
Cross Section of a Volcano Dust
Volcanic Ash
Volcanic bomb
Lava
Vent
Magma Chamber
Crater
Layers of ash and lava
Volcanic cone/ Secondary cone
Crust
10 Volcanoes to Remember
North AmericaSouth AmericaAfrica
Europe
AsiaAustralasia / Oceania
Mt St HelensPopocatepetlMontserrat
AconcaguaHeimaey
Vesuvius
KrakatoaPinatuboMauna Loa
Mt Fuji
Answers
Two different shapes of volcano
• Shield volcanoes are usually found at constructive boundaries.
• They are low, with gently sloping sides.
• They are formed by eruptions of thin, runny lava.
• Eruptions tend to be frequent but relatively gentle.
• E.g Mauna Loa in Hawaii
• Composite volcanoes are made up of alternating layers of lava and ash (other volcanoes just consist of lava).
• They are usually found at destructive boundaries.
• During eruption pyroclastic flow can roll down the sides of a volcano at very high speeds and with temperatures of over 400°C.
• A pyroclastic flow is a mixture of hot steam, ash, rock and dust.
• Mt Pinatubo, in the Philippines
Page 226 Question 8
Case-study of Mount Saint Helens
Question 8 d)Eruption of May 1980
Colliding Plates
• Two continental plates converge • Both plates are not heavy enough to be pulled down into the
mantle• No where to go, plates buckle up and form folded mountain
ranges• In this area there are powerful earthquakes but no volcanic
eruption • For example: Himalayas (Pakistan) and the Alps (North Italy)
Sliding plates / conservative boundary
Pacific Platemoving faster than North American plate
North American PlateMoving slower than Pacific Plate
San Andreas Fault Line
Other section of North American Plate sliding in opposite direction
*San Francisco
*Los Angeles
• Tectonic plates move in different directions, or at different speeds• Plates become locked/jammed together • Pressure builds until rock snaps along a fault line • Plates move suddenly, causing powerful earthquakes• For example along the San Andreas Fault line in California
Earthquake and Tsunami Case study of Japan
Earthquakes
Earthquakes are caused by the sudden movement of the tectonic plates which make up the Earth's crust.
Earthquakes
Earthquakes produce shock waves. These travel through the Earth and can be detected using a device called a seismometer.
Plates are moving in opposite direction or at a different speed (pressure builds-up in the crust)
Pressure becomes too much and it is suddenly released
Focus is where the rocks suddenly move and start the earthquake
*Epicentre
Epicentre is the place on the earth’s surface directly above the focus. It receives the strongest shockwaves
Sliding plates
Earthquake is measured on the Richter scale
Earthquake on 11th of March 2011 was magnitude 9