Plate Tectonics Flashcards
what is the main evidence for plate tectonics and continental drift
Seafloor spreading
Why do magnetic reversals matter in MOR
Magnetic reversals(= a switch in the Earth’s magnetic field)were detected in bands parallel to mid-ocean ridges.
What are earths chemical layers
Crust
Mantle
Core
What is the core of the earth made of
outer liquid layer of iron and nickel and a solid inner core of metallic iron.
What are the five main physical layers of the earth and what major element determines them.
- Lithosphere
- Asthenosphere
- Mesosphere
- outer core
- Inner core
and are determined by responses to stress
what drives plate tectonics
Mantle Convection: arm material rises under mid-ocean ridges, cools and then sinks at subduction zones; conveyor belt analogy
Define Lithosphere
the lithosphere is the outermost physical layer of the Earth. It is grouped into two types: oceanic and continental. Oceanic lithosphere is thin and relatively rigid. It ranges in thickness from nearly zero in new plates found around mid-ocean ridges, to an average of 140 km in most other locations. Continental lithosphere is generally thicker and considerably more plastic, especially at the deeper levels. Its thickness ranges from 40 to 280 km
Define Asthenosphere
The asthenosphere is the layer below the lithosphere. Astheno- means lacking strength, and the most distinctive property of the asthenosphere is movement. Because it is mechanically weak, this layer moves and flows due to convection currents created by heat coming from the earth’s core cause. Unlike the lithosphere that consists of multiple plates, the asthenosphere is relatively unbroken.
Define Mesosphere
The mesosphere, sometimes known as the lower mantle, is more rigid and immobile than the asthenosphere. Located at a depth of approximately 410 and 660 km below the earth’s surface, the mesosphere is subjected to very high pressures and temperatures. These extreme conditions create a transition zone in the upper mesosphere where minerals continuously change into various forms, or pseudomorphs
How did alfred wagner influence plate tectonics
He introduced the concept of continental drift to the literature. However initially he was considered to be crazy.
define continental drift
the theory that continents were initially put together like jigsaw pieces and overtime drifted apart.
Define Wadati-Benioff zone
Several independent research groups recognized earthquake epicenters traced the shapes of oceanic plates sinking into the mantle. These deep earthquake zones congregated in planes that started near the surface around ocean trenches and angled beneath the continents and island arcs. Today these earthquake zones called Wadati-Benioff zones.
What is a mid ocean ridge (mor) and how does it work
A divergent boundary within an oceanic plate, where new lithosphere and crust is created as the two plates spread apart. Mid-ocean ridge and spreading center are synonyms.
Why does earths polarity matter
while parts of Earth’s outer core are too deep for scientists to measure directly, we can infer movement in the core by observing changes in the magnetic field.
define active and passive margins
Active margins are places where the oceanic and continental lithospheric tectonic plates meet and move relative to each other
At passive margins the plates don’t move—the continental lithosphere transitions into oceanic lithosphere and forms plates made of both types. A tectonic plate may be made of both oceanic and continental lithosphere connected by a passive margin.
Define divergent boundaries
At divergent boundaries, sometimes called constructive boundaries, lithospheric plates move away from each other. There are two types of divergent boundaries, categorized by where they occur: continental rift zones and mid-ocean ridges
define convergent plate boundariers
Convergent boundaries, also called destructive boundaries, are places where two or more plates move toward each other. . Convergent boundary movement is divided into two types, subduction and collision, depending on the density of the involved plates
Define subduction and explain subduction zones
Subduction occurs when a dense oceanic plate meets a more buoyant plate, like a continental plate or warmer/younger oceanic plate, and descends into the mantle.
It is generally accepted that subduction zones start as passive margins, where oceanic and continental plates come together, and then gravity initiates subduction and converts the passive margin into an active one
define transform fault boundaries
A transform boundary, sometimes called a strike-slip or conservative boundary, is where the lithospheric plates slide past each other in the horizontal plane.
Some transform boundaries produce significant seismic activity, primarily as earthquakes, with very little mountain-building or volcanism. This type of transform boundary may contain a single fault or series of faults, which develop in places where plate tectonic stresses are transferred to the surface
Which kind of plate boundary is associated with earthquake activity?
Subduction zones
Which kind of plate boundary is new oceanic lithosphere formed?
Mid ocean ridge
what is wilsons cycle
The Wilson Cycle is named for J. Tuzo Wilson who first described it in 1966, and it outlines the ongoing origin and breakup of supercontinents, such as Pangea and Rodinia. Scientists have determined this cycle has been operating for at least three billion years and possibly earlier.
Define hotspots
First postulated by J. Tuzo Wilson in 1963, a hotspot is an area in the lithospheric plate where molten magma breaks through and creates a volcanic center, islands in the ocean and mountains on land. As the plate moves across the hotspot, the volcano center becomes extinct because it is no longer over an active magma source. Instead, the magma emerges through another area in the plate to create a new active volcano.
What is the approximate velocity of the fastest-moving tectonic plates on Earth?
138-150 mm/y
James Hutton***test question
Created Uniformitarianisim
Uniformitarianism
Principle of Uniformitarianism
Idea championed by James Hutton that the present is the key to the past, meaning the physical laws and processes that existed and operate in the past still exist and operate today.
