Lecture 5: Plate Techtonics Flashcards
What are the 2 types of Divergent boundaries?
- Ocean spreading center
* Continental rift zone
What is a divergent boundary: Oceanic Spreading center?
Rifting and spreading along a mid-ocean ridge creating new oceanic lithosphere
What occurs in sea-floor spreading?
At mid ocean ridges, the release of pressure as the plates move apart allows hot magma from the asthenosphere to reach the ocean floor which cools and crystallizes to form a new lithosphere
Which crust is the least stable?
Ocean crust is the least stable and subducts because it is more dense
What is divergent boundaries: Continental Rifting?
Mantle material also rises from near the core-mantle boundary in the form of thermal plumes. When the plume nears the lithosphere it spread it laterally moving segments outward and can form new oceanic tracts
What is the Wilson cycle?
The opening of new ocean basins along divergent zones, the expansion of the basin as seafloor spreading continues and the ultimate closure of the basin as the plate converge
What are the 3 types of Convergent boundaries?
- Ocean-Continent
- Ocean-Ocean
- Continent-Continent
What occurs in ocean continent convergence?
Oceanic lithosphere is subducted and a volcanic mountain belt is formed at the continental margin. The oceanic plate is melted and reincorporated into the asthenosphere
When do Island-Arcs form?
In ocean ocean convergence where a plate is melted and emerges as lava
What kind of Boundary is Marianas trench?
Ocean-Ocean
What occurs in Ocean-Ocean convergence?
The older denser plate sinks below the younger less dense plate forming island-arcs
What occurs in Continent-Continent boundaries?
Two landmass come together to form a mountain range because both plates are too buoyant to sink into the mantle
What is a Craton?
The oldest part of a continent, formed, evolved and altered over billions of years
What are Orogens?
Bands of mountains
What is a Continental Sheild?
An assemblage of ancient cratons and orogens
