The Seafloor Flashcards
Percentage of earth’s surface area covered by water
71% and ~95% of inhabitable volume
Four major ocean basins
Pacific, Atlantic, Indian and Arctic
Earth core
~ 3400 km thick
Solid inner core and liquid outer core
Iron rich
Oceanic crust
Mostly Basalt
Denser than continental crust
Relatively young less than 200 million years old (because it’s denser it’s on the conveyor belt to be formed and destroyed )
Continental crust
Mostly granite
Less dense than oceanic crust
Up to 3.8 billion years old
How many tectonic plates are there
12 major tectonic plates
Divergent boundaries
Occurs when two tectonic plates move away from each other
As plates move apart new crust is formed usually around mid ocean ridges
Convergent boundaries
Two plates move towards each other,
Continent-Continent Collison
Two continental plates move towards each other, both plates are less dense so the plates collide and push upwards forming large mountain ranges (European Alps and Himalayas)
Continent-Oceanic crust collison
Oceanic crust subducts (more denser) under the continental crust
Results in the forming of volcanism, deep trenches and subduction zone creates mountains ranges (South America Andes)
Ocean-Ocean plate collision
Two oceanic plates collide, one runs over the other which causes it to sink onto the mantle forming a subduction zone
The subduction plate is bent downward to form a very deep depression in the ocean called trench
Transform Boundaries
Two plates slide past each other, may occur either on land or underwater
Such moments is rarely smooth and may cause tsunamis or earthquakes (San Andreas fault)
Mid-Ocean Ridges
A continuous chain of submarine volcanic mountains that encircle the globe like seams on a baseball
Rifts
Formed between plates at divergent boundaries (spreading centers)
Allows magma to side through rift, pushes up surrounding oceanic crust and cools to form new crust
Crust age: near ridges
Young rock and little sediment accumulation
