Presentation on theme: "4 Layers of the earth 7 main plates of the earth 3 main plate boundaries 2 types of crust 3 main features of plate tectonics (F.E.E.D) 3 main theorists."— Presentation transcript:
4 Layers of the earth 7 main plates of the earth 3 main plate boundaries 2 types of crust 3 main features of plate tectonics (F.E.E.D) 3 main theorists and theories Human interaction
The Earth is made up of 3 main layers: Core Mantle Crust (Lithosphere and the Athenosphere) Inner core Outer core Mantle Crust
“Plates” of lithosphere are moved around by the underlying hot mantle convection cells
This is where we live! The Earth’s crust is made of: Continental Crust - thick (10-70km) - buoyant (less dense than oceanic crust) - mostly old Oceanic Crust - thin (~7 km) - dense (sinks under continental crust) - young
Plates are made of rigid lithosphere. The lithosphere is made up of the crust and the upper part of the mantle.
Below the lithosphere (which makes up the tectonic plates) is the asthenosphere.
Constructive (known as Divergent) Destructive (known as Convergent) Transform/Passive/ Neutral/Conservative Three types of plate boundary
Spreading ridges As plates move apart new material is erupted to fill the gap Constructive Boundaries
Age of Oceanic Crust
Can you find ICELAND?
Iceland has a divergent plate boundary running through its middle Iceland: An example of continental rifting
There are three styles of destructive/convergent plate boundaries Continent-continent collision Continent-oceanic crust collision Ocean-ocean collision Destructive Boundaries
Forms mountains, e.g. European Alps, Himalayas Continent-Continent Collision
Called SUBDUCTION Continent-Oceanic Crust Collision
Oceanic lithosphere subducts underneath the continental lithosphere Oceanic lithosphere heats and dehydrates as it subsides The melt rises forming volcanism E.g. The Andes Subduction
When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone. The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench. The worlds deepest parts of the ocean are found along trenches. E.g. The Mariana Trench is 11 km deep! Ocean-Ocean Plate Collision
Where plates slide past each other Neutral / Transform Boundaries Above: View of the San Andreas transform fault
If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.
The study of plate tectonics has been furthered by the work of three main theorists. Alfred Wegener – a German Meteorologist Maurice Ewing – an American oceanographer/geophysicist Harold H. Hess – Professor of Geology, Princeton, USA
In his published work “The origins of continents and Oceans” (1912) Wegener proposed that millions of years ago all the continents of the earth were once joined together in one large land mass called….Pangea
Slowly, due to magma convection currents deep within the mantle, Pangea broke into two large continents called Laurasia and Gonwanaland. Over millions of years these two broke and moved into the main continents we know today.
Same fossils and rocks found in different parts of the world Africa and South America look like pieces of a jigsaw
Some people thought the Earth was shrinking and cracking Wegener thought whole sections of the crust moved (plate tectonics) Some people did not understand and thought the continents floated around in the oceans (continental drift) He died before people accepted his ideas
Ewing studied and photographed much of the earths ocean floors. Once, during a trans- Atlantic flight, he looked down and noticed a dark shadow running along the Atlantic Ocean. Research showed that the American and Eurasian plates were separating and new crust was forming. Layers and ages of each new magma flow showed the widening of the sea floor over millions of years.
Hess was an American professor who furthered the study of plate tectonics with his theory of Sea Floor Spreading and the creation of new crust and volcanic ridges.
Alfred Wegener (1912) – Continental Drift Maurice Ewing (1947) – Mid Atlantic Ridge Harry Hess (1960s) – Sea Floor Spreading All combined, plus the study of countless others, creates the Theory of Plate Tectonics
Volcanoes Earthquakes Fold Mountains
Plates moving in any direction causes earthquakes The worst are caused by plates rubbing past each other as in C This happens along the Californian coast
Large continents begin to crack and split apart The gaps fill with water Small seas become oceans The mid ocean ridge continues to produce new crust
Why is the Atlantic still getting wider The plates are pulled apart by convection currents in the mantle below Caused by heat released from natural radioactive processes At the mid Atlantic ridge molten rock from below rises up to fill the gap with new basaltic rock
More evidence has been found for Wegener's theory The Earths North and South pole have flipped many times These leaves magnetic ‘stripes’ in rock containing iron minerals
Dense heavy oceanic crust can be subducted below less denser continental crust. The friction melts rock This magma rises through the crust to form new volcanoes This is happening in South America (The Andes)
Eventually when plates move together the continental crust collides The heat and pressure make metamorphic rock It also pushes and folds the rocks into high mountains The Himalayas rise to 8848m and are still growing today
…what’s the connection? Volcanoes and Plate Tectonics…
Volcanism is mostly focused at plate margins Pacific Ring of Fire
- Subduction - Rifting - Hotspots Volcanoes are formed by:
Pacific Ring of Fire Hotspot volcanoes
Hot mantle plumes breaching the surface in the middle of a tectonic plate What are Hotspot Volcanoes? Photo: Tom Pfeiffer / The Hawaiian island chain are examples of hotspot volcanoes.
The tectonic plate moves over a fixed hotspot forming a chain of volcanoes. The volcanoes get younger from one end to the other.
…what’s the connection? Earthquakes and Plate Tectonics…
As with volcanoes, earthquakes are not randomly distributed over the globe At the boundaries between plates, friction causes them to stick together. When built up energy causes them to break, earthquakes occur. Figure showing the distribution of earthquakes around the globe
Figure showing the tectonic setting of earthquakes
The Earth is made up of 3 main layers (core, mantle, crust) On the surface of the Earth are tectonic plates that slowly move around the globe Plates are made of crust and upper mantle (lithosphere) There are 2 types of plate There are 3 types of plate boundaries Volcanoes and Earthquakes are closely linked to the margins of the tectonic plates