topic 4 plate tectonics Flashcards
Landforms are the result of what major groups of processes?
Land building: volcanic and tectonic forces (initial landforms ‘primary’) and Land denudation: weathering and erosion (sequential landforms ‘secondary’)
Landforms reflect a balance between internal earth forces and bring fresh rock to the surface and denudation processes that remove and transport mineral matter
what transports the most rock and soil annually?
- rivers 53 billion tons 2. humans 45 billion tons 3. oceanic volcanoes 30 billion tons 4. mountain building 14 billion tons 5. glaciers 4.3 (10) billion tons
earth structure
Core, mantle, and crust/lithoshere
increasing temperature and density of material with depth
Continental drift
the idea that all landmasses were once all one large continent, pangea, surrounded by a single ocean.
Pangea broke apart over hundreds of millions of years ago because of development of rift zones within continents
continents spread apart and ocean basins developed by process of sea-floor spreading
plate tectonics
The theory describing the origin, movement, and recycling of lithosheric plates and the resulting landforms
origin was the theory of seafloor spreading; new lithosphere forms at mid-ocean ridges, and old lithosphere is recycled deep into the mantle through subduction
what is subduction?
the process in which oceanic lithosphere from one plate bends and dives into the mantle beneath another plate
subduction only occurs where Oceanic lithosphere subducts beneath continental lithosphere/oceanic lithosphere
concept of a lithospheric ‘plate’
Rigid lithospheric rocks are “floating” on the denser, plastic asthenosphere
The lithosphere is broken into large plates (AKA ‘tectonic’ plates)
plates are flexible yet brittle (fractures are known as “faults”)
Two types of plates
14 total plates (7 primary plates, 7 secondary plates)
Primary plates: the African plate, Antarctic plate, Eurasian plate, Indo-Australian plate, North American plate, Pacific plate, and the South American plate
secondary plates: the other 7
How to find plate boudaries?
Earthquake activity reveals plate boundary locations
Earthquakes occur in geographic patterns that delineates the outlines of lithospheric plates
How do plates move?
Ridge push: rising magma along a mid-ocean ridge lifts oceanic lithosphere and forms slopes
mantle drag: movement of plates caused by friction between moving asthenosphere and the lithosphere
Slab pull: the weight of the subducting portion of a plate accelerates plate movement by pulling the plate deeper into the mantle
absolute velocity
how fast the plate is moves in relation to a fixed point
Relative velocity
How fast a plate moves in relation to the speed of an adjacent moving plate
What is uplift?
change in land/rock surface vertical position relative to a fixed datum (e.g. sea level)
Total uplift
the sum of Tectonic uplift (due to collisions and tectonic movements) and isostatic uplift (due to the difference in density between mantle and the crust)
when erosion occurs, there is an isostatic adjustment (due to the difference in density between crust and mantle). for each meter of erosion, isostatic response lifts the underlying rock up by ~82cm
Plate boundaries
Divergent: where two plates move apart
Convergent: where two plates move towards each other
transform: where one plate slips laterally past another
Divergent boundary Landforms
mid-ocean ridges (~underwater mountains): rising magma pushes up, which pushes the slab outward
Rifting: region where continental crust is stretching and splitting.
Rift valley is a long valley with volcanoes formed by rifting of continental crust. may flood with seawater, creating an inland sea and, with more time, a new ocean basin
types of convergent plate boundaries
Continental-Continental; Oceanic-Oceanic; and Oceanic-Continental
What forms along convergent plate boundaries where subduction occurs?
Explosive Volcanoes form along convergent plate boundaries
Can continental lithosphere subduct?
Continental lithosphere cannot subduct because it is less dense than oceanic lithosphere
How is oceanic crust recycled?
as the oceanic lithosphere is subducted, it is consumed and recycled as mantle convection occurs, the rich minerals of the mantle surfaces as crust-making lava at mid-ocean ridges and volcanoes
Flux melting
the process in which the mantle mixes with seawater and melts into magma (occurs only in subduction zones)
Volcanic arc
a long chain of volcanoes on the margin of a continent where subduction is occurring
magma rises up, melting its way through margin of continental crust, producing a volcanic arc
Where does continental arcs form?
Continental arcs are a long chain of volcanoes that form only on the margins of a continent where an oceanic plate subducts beneath continental plate
How do island arcs form?
Island arcs are a chain of volcanic islands formed when oceanic lithosphere subducts beneath oceanic lithosphere of another plate
