Lecture 22 Flashcards
What world event lead to people deciding to map the oceanic floor?
World War II and the fight between the allied ships and Nazi U-Boats.
What is most of the surface of the Atlantic Ocean made up of?
Alibnar Plane
What is the Mid-Oceanic Reach?
Mountain chain in ocean that paralls the shores of North and South America, and Europe and Africa
What was the first ocean that the deep sea drilling project drilled into?
Atlantic Ocean
What was discovered about Earth’s Magnetic Field?
Depostion and minerals formed clasts. Act as dipoles and align themselves with the lines of the magnetic field. At a certain depth, however, minerals alignments rotated, Then switched back, then rotated, etc.
What are the 2 types of magnetic polarity?
Normal and Reversed
What is normal polarity?
Northern magnetic pole is close to northern geographical pole, and same with the south
What is reversed polarity?
Rotated 180 degrees. South magentic pole is close to north geographical pole and same with the other.
How does polarity shift in the ocean?
Proximity of mid oceanic reach = normal polarity. As you move outwards, it reverses. Then switches.
Where does the oceanic crust form?
At the mid-oceanic reach.
What is Paleomagnetism?
Distribution of the polarity zones at the sea floor.
Where are the youngest sediments in the ocean situated?
Exactly in the proximity of mid oceanic reach
Where are the oldest sediments in the ocean situated?
In the proximity of the continental margins.
How does an Ocean form (Oceanic formation model)
Evolution of an ocean begins in the zone with the continental crust. Ascending currents of the athenosphere push on the crust and stretches the slab, making it thinner. Depression zones form and continent is filled with freshwater. Lots of volcanic activity. Becomes salty as oceanic water moves in. Ascending currents continue. Volcanic rocks with mantle composition occur in continental zone. Basic magma that forms basalts. New matter at surface crystallizes and oceanic crust forms, Continents move away, mid-oceanic reach forms.
What is the East African Rift?
An example of modern rifting. Vast Depression zones. Lots of volcanic activity and earthquakes. Vast accumulation of water. HUGE LAKES.
What does it mean that the East African Rift has stratified waters?
Waters that are oxygenated ar the surface and toxic at the bottom. Gases from inner earth reach surface and dissolve..
What is the Red Sea?
Sea situated between Africa and Arabian Peninsula. An ocean that is in incipient formation due to the break up of a continent.
What are the consequences of the mid-oceanic reach being unstable in the red sea?
Fracture continues moving.
What are the 5 stages of rifting in an ocean?
1) Pre-rifting
2) Continental Uplift
3) Continental Rift
4) Early Oceanic Basin Formation
5) Mature Oceanic Basin
What is pre-rifting?
When the ocean formation has not yet started
What is the continental uplift?
Begins with ascending currents from Asthenosphere. Continent is uplifted, Continental crust gets thin
What is a continental rift?
Crust thins and continent begins to split
What is the early oceanic basin formation?
Narrow, elongated basin floored with oceanic crust, framed by continents
What is the mature oceanic basin?
When an ocean actually forms.
Which stage marks the beginning of ocean formation?
Continental uplift
Where do we study the consumption of the Atlantic ocean?
In the Pacific Ocean
What is the zone of subduction?
When the pacific plate is sunken under the North American and Eurasian plate. Transition is gradual
What was discovered in the Aleutian Island Arc?
Volcanoes and Earthquakes. Hypocentres of these aligned to form a plane,
What is the Benioff Plane?
Plane of subduction. Exists everywhere around the pacific. Sinks under Eastern Coast of Asia and Australia and Southern North America and South America.
What is consumption?
When one slab of oceanic crust is completely subducted under continental plate. Entire fossil records are destroyed. Subduction is responsible for volcanic mountains in surrounding area.
What happened when an entire ocean was consumed during the Collision of India and Eurasian plates?
Ocean in between was closed, huge mountain range was formed (Geologically, India is a separate continent)
Where did Italy originally come from?
Came from Africa and collided with Europe to form the Alps.
What happened when Spain collided with Eurasia?
The Pyrannese formed
What happend when Greece collided with Eurasia?
Formed Balkan mountains.
Where are Italy, Spain and Greece all from and what does this tell us?
Africa. In the next 25 million years, Africa will collide with Europe.
What is the Wilson Cycle?
Cycle of birth, formation, evolution, and close-up of oceaninc basin-defined Paradigm of Plate Tectonics
What is the Paradigm of Plate Tectonics?
Formation of ocean and movement of continents. Relates to Theory of Evolution.
Why does the Paradigm of Plate Tectonics relate to the Theory of Evolution?
Onset of modern plate tectonics put pressure on life forms. Without it, life would be very simple.
