Plate Tectonics Flashcards
Mid-Atlantic Ridge
basaltic mountain range that spans the length of the Atlantic ocean w/rock chemistry and dimensions unlike mountain ranges found on continents
Plate Tectonics
The theory that the outer layer of the earth (lithosphere) is broken in several plates, and these plates move relative to one another causing the major topographic features of the earth and most earthquakes and volcanoes.
Oceanic Crust
Thin, outer layer of the earth which makes up the rocky bottom of the ocean basins. It is made of rocks similar to basalt. And as it cools becomes even more dense than the upper mantle below.
Transform definition
Place where 2 plates slide past each other, creating strike slip faults
-Most transform boundaries are found on ocean floor, around mid-ocean ridges.
Chemical Layers of the Earth
Crust
Mantle
Core
Crust
the outermost chemical layer of the earth. As defined by its low density and higher concentrations of lighter elements. 2 types oceanic and continental
Moho
Short for mohorovicic. The seismically recognized layer within the earth in which the crust ends and the mantle begins.
Mantle
Largest chemical layer by volume.
Middle chemical layer. Made of mainly iron and magnesium silicates. It is generally denser than the crust (except older oceanic crust) and less dense than the core.
Core
- Looking at seismic date first discovered in 1906
- The innermost chemical layer of the Earth. made chiefly of iron and nickel. Both liquid and solid components.
Physical Layers of the Earth
5 Distinct Physical Layers base on how each layer responds to stress.
- Lithosphere
- Asthenosphere
- Mesosphere
- Outer Core
- Inner Core
Lithosphere
The outermost physical layer of the earth. Made of the entire crust and upper mantle. It is brittle and broken into a series of plates. These plates move in various ways
Asthenosphere
A ductile physical layer of the earth. Below the lithosphere. Movement within is the main driver of plate motion, as the overriding lithosphere is pushed by this.
- Mechanically weak
- Moves due to convection currents
- Relatively unbroken
Mesosphere
- Also called lower mantle.
- A solid, more brittle physical layer of the earth.
- Below Asthenosphere
Outer core
The outer physical layer of the core.
- Liquid
- responsible for magnetic field and flips of it
- If it were to stop moving or become solid it would result in loss of magnetic field and would result in Earth getting stripped of life-supporting gases and water. This is what happened to Mars
Inner Core
The innermost physical layer of the earth. It is solid
-Hottest part of the earth is solid. The minerals making it up should be liquified or vaporized at this temp but the immense pressure keeps them solid.
Passive Margin
A boundary between continental and oceanic plates that has no relative movement. Making it a place where an oceanic plate is connected to a continental plate. BUT it is not a plate boundary
The 3 Types of Tectonic Plate Boundaries
- Divergent
- Convergent
- Transform
Convergent Definition
Place where two plates come together. Causing subduction or collision.
AKA Destruction boundaries
Divergent Definition
Place where two plates are moving apart. Creating either rift (continental lithosphere) or a mid-ocean ridge
Transform Definition
Place where two plates slide past each other. Creating strike slip faults.
- Most transform boundaries are found on the ocean floor, around mid-ocean ridges.
- Significant seismic activity. Very little mountain building or volcanism
Subduction definition
Oceanic plate descends below a less dense plate. Causing the removal of the plate from the surface.
- Causes the largest earthquakes possible
- Volcanoes
Trench
Deepest part of the ocean where a subducting plate dives below an overriding plate.
Accretionary Wedge
Mix of sediments that form as a subducting plate descends and the overriding plate scrapes material and material is added.
Terrane
A geological province which is added (accreted) to a continental mass via subduction and collision
Slab
A name given to the subducting plate. Where volatiles are driven out at depth. causing volcanism
Mantle Wedge
The area of the mantle where volatiles rise from the slab. Causing flux melting and volcanism
Flux Melting
The process in which volatiles enter the mantle wedge and the volatiles lower the melting temperature causing volcanism.
Volatiles
Components of the magma which are dissolved until it reaches the surface, where they expand
Volcanic Arc
Place with a chain of mountain volcanism on a continent. From Oceanic-Continental subduction
Forearc Basin
Any depression formed between the arc and the trench. Commonly between the arc and accretionary wedge.
All subductuib zones have a forearc basin. Between thr volcanic arc and oceanic trench.
-experiences a lot of faulting and deformation activity
Back-Arc basin
A lot of faulting and deformation activity
Extension- subduction— volcanic arc gets stretched until it cracks and collapses to form a back arc.
**back arc basin can develop into continental rifting zone.
Thrust Faults
AKA Compressional back arc faults
A lower-angle reverse fault. Common in mountain building
Thin-Skinned - Faulting that is not dep into the crust. Typically only involves sedimentary cover. Not basement rocks
Thick-skinned- Faulting that is dep into the crust. And typically involves crystalline basement rocks
Orogeny
The process of uplifting mountain within mountain belts. Primarily via tectonic movement. Mountain belts are the result from movement.
Collision
When two continents crash with no subduction (Thus little to no volcanoes) since each continent is too buoyant. Many of the largest mountain ranges and broadest zones of seismic activity come from collisions.
Obduction
Process which allows a continental plate to bring up an oceanic plate. Frequently occurring in collision zones.
Rift
Area of extended continental lithosphere. Forming a depression. Rifts can be narrow (focused in one place) or broad (spread out over a large area with many faults)
Graben, half-graben, horst
Graben
A valley formed by normal faulting
Half-Graben
A valley formed by normal faulting on just one side.
Horst
Uplifted mountain block caused by normal faulting
Decompression
melting that occurs as material is moved upward and pressure is released. Typical found at divergent boundaries or hot spots
As a rift forms on a continent, what feature can form next?
Ocean basin
How is magma generated at divergent boundaries?
Decreased pressure
Dextral
Movement in a transform setting which it moves toward the right across the fault. As viewed across the fault. Objects will move to the right
Sinistral
Transform motion in which the relative motion is to the left. As viewed across the fault, objects will move to the left.
Transpression
A segment along a transform which has a compressional component, sometimes creating related thrust faulting and mountains
Transtension
A place along a transform with an extensional component, sometimes including normal faulting, basin formation, and volcanism.
Piercing Point
An object that is cut by a fault which allows the amount of movement to be determined. This is useful for all faults but more commonly used in strike-slip faults.
What famous transform fault is known for being the boundary between the pacific plate and the North American plate?
San Andreas Fault
What are the two ways transform faults move?
Left (sinistral) and right (dextral)
Why are piercing points important with transform boundaries?
They track the movement
What makes transform boundaries different from other boundaries?
Transform has less volcanoes
Wilson Cycle
J. Tuzo Wilson
the cycle of opening ocean basins with rifting and seafloor spreading then closing the basin via subduction and collision, creating a supercontinent.
-Operating at least 3 billion years
Hot Spots
Rising stationary magma, forming a succession of volcanism. this is reflected as islands on oceanic plates, and volcanic mountains or craters on land
- Only type of volcanism not associated with subduction or rifting zones.
- Seems totally disconnected from any plate tectonics processes.
- We do not know what causes them
- Active volcanoes over hot spot with extinct extending in a line that shows the movement of the plate
Tomography
A process of using 3D seismic arrays to get subsurface images
According to the Wilson Cycle, what feature or process is most likely to occur after collision and formation of a supercontinent?
Rifting
What features or processes are common in hot spots?
volcanism
What makes the Hawaiian hot spot different than the Yellowstone hot spot?
Different types of tectonic plates
Which tectonic setting places the asthenosphere farthest from the surface?
Continental collisions
A line of shallow earthquakes with little or no volcanism is likely evidence of what type of plate boundary?
Transform