WEEK 4- TECTONIC PLATES Flashcards
an undifferentiated, homogenous
mass of solid rock when it was formed 4.5 BYA.
Earth
denser materials sank—less dense materials displaced towards the surface.
Iron Catastrophe
Liquid layer
Mantle
Part of mantle with convection currents
Asthenosphere
solid layer made up of iron and nickel
Inner core
two types of crust
Oceanic and Continental Crusts
liquid layer made up of iron and nickel
Outer core
basalt, 4-7km thickness, much denser(heavier) than continental crust, subducts underneath the continental crust.)
Oceanic
granite, 20-70km thickness, less dense(will not undergo subduction, lighter.
Continental
Proposed by Alfred wegener
Continental drfit theory
he believed that all the continents were connected as one large land mass (Pangea) about 200 million years ago.
Alfred Wegener
Continents were once a supercontinent called _____ which means “all lands.” Over time, these supercontinents slowly broke apart into what we have today.
Pangaea
Evidences of continental drift theory:
Distribution of rocks, distribution of fossils, distribution of glacier sediments, paleoclimate, fit of continental shorelines
these were the main evidence for continental drift during Wegener’s lifetime.
Fossils, rocks, climate clues
This theory was often rejected because no one could explain how the continents moved. He reasoned that the cause of movements is the Earth’s Rotation.
Continental drift theory
Why was Wegener’s theory often rejected?
No one could explain how continents are moving
Some terrestrial organisms are restricted in certain continents because they cannot
swim and cross over the vast oceans that
PRESENTLY separate the continents.
Distribution of fossils
Coal forms in tropical climates
Paleoclimate
Orientation of striations or scratches imprinted as glaciers moved along the surface of rocks
Distribution of glacier sediments
For example, the coast of Africa fits well with the Eastern coast of South America and Southeast coast of North America
Fit of continental shorelines
Parts of the Appalachian mountains in the
eastern America are like those found in
Greenland and western Europe
Distribution of rocks
It is the idea that the Earth’s crust and upper mantle are broken into sections called plates that move around on the mantle.
Theory of plate tectonics
It is the idea that the Earth’s crust and upper mantle are broken into sections called _____ that move around on the mantle.
Plates
Plate boundaries (3)
Divergent, convergent, transform
Boundaries between two plates that are diverging or moving away from each other
Divergent
the crust and part of the upper mantle
Lithosphere
the plastic like layer below the lithosphere
Asthenosphere
2 composition of earth’s plates?
Lithosphere and asthenosphere
fossils (especially rocks) formed million years ago and contain record of direction of the magnetic poles at the time of formation.
Paleomagnetism
it is the driving force of plate tectonics in which hot, plastic-like material from the mantle rises to the lithosphere, moves horizontally, cools, and sinks back to the mantle.
Convection current
often occur along faults. Faults are breaks in rock mass where plate movement occurred. Faults are associated with plate boundaries.
Erathquakes
Boundaries between two plates that are sliding horizontally past one another.
Transform fault
The crust is broken up into sections that moves on top of liquid mantle
Plates
Boundaries between two plates that are converging or moving towards each other
Convergent
sections or pieces of crusts are called
Tectonic plates
Forms trenches, Destructive Earthquakes, Rapid Uplift of mountain ranges, and building of volcanic arc
Oceanic-continental
Produces trenches and volcanic arcs
Oceanic-oceanic
Produces mountain ranges (himalayas)
Continental-continental
San Andreas fault
Transform
Proposed by Harry Hammond Hess
Sea floor spreading
Presented a mechanism how Pangaea broke apart
Sea floor spreading
Both sides moves away from crust until it sank
Subduction
Recite the 6 stages of Wilson cycle
Embryonic, Juvenile, Mature, Declining, Terminal, Continental collision
seafloor basalts begin forming as continental margins separate. Rift valley deepens and is flooded by seawater.
Juvenile
Wilson cycle begins with-
a rising plume of magma and the thinning of the overlying crust.
The cyclical opening and closing of ocean basins caused by the movement of the Earth’s plates.
Wilson cycle
broad ocean basin widens, trenches develop, and subduction begins.
Mature
continents are starting to separate resulting in the formation of rift valleys.
Embryonic
subduction narrows much of the seafloor and oceanic ridge due to converging tectonic plates. This results in the formation of trenches, volcanic island arcs, and coastal mountain ranges.
Declining
ocean basin becomes narrow and shallow due to sedimentation. Young m mountain ranges are formed along the sides.
Terminal
the remaining seafloor is eliminated and continents collide, forming a continental mountain chain.
Continental collision
2 classifications of faults:
Strike slip and dip slip faults
Under dip-slip faults are:
Reverse, normal, and thrust
Faults in which movement is primarily parallel to the dip (or inclination) of the fault surface are called?
Dip-slip faults
Fractures that has no movements
Joints
Fractures in the crust along which appreciable displacement has taken place
Faults
a block that moved down between to subparallel normal faults that dip towards one another
Graben
These are dip-slip faults in which the hanging
wall moves down to the footwall
Normal faults
these are dip-slip faults which the hanging wall block moves up to the footwall block.
Reverse faults
consist of two subparallel fault that dip towards each other so that the block between remain high
Horst
Are reverse faults having dips less than 45°, so the overlying block moves nearly horizontally over the underlying block.
Thrust faults
A fault in which the dominant displacement is
horizontal and parallel to the trend or strike of the fault surface
Strike-slip faults
The rocks are sliding past each other horizontally, with little to no vertical movement.
Strike slip faults
2 classifications of strike-slip:
Dextral or sinistral
when some strike-slip faults cut through the lithosphere and accommodate motion between two large tectonic plates
Transform fault
Ex. The 1,200 km Philippine Fault Zone (PFZ) that transects the Philippines from Luzon to Mindanao
Left lateral strike-slip or sinistral
A strike-slip fault where the block opposite an observer looking across the fault moves to the left
Left lateral strike-slip or sinistral
A strike-slip fault where the block opposite
an observer looking across the fault moves
to the right
Right-lateral strike-slip of dextral
EX. San Andreas Fault
Dextral
bending or warping of rock strata caused by
compressive stress. The structure that develops is called_____?
Folding, fold
Parts of a fold
Limbs, axis, axial plane
The axes of most folds are inclined. The angle of dip of its axis is the_____?
Plunge
Imaginary plane containing all the fold axes within a deformed layer of rock layers
Axial plane
Two sides or legs of folds
Limbs
Fold types (2)
Anticline and Syncline
Through shaped fold
Syncline
Symmetrical fold in which one limb has been tilted beyond veritcal
Overtuned fold
Arch shaped fold
Anticline
Direction of imaginary line connecting points of maximum flexure of fold
Axis
Bed in a generally flat-lying rock layer
Monocline
If one limb is steeper, the fold is?
Asymmetrical
Anticlines and synclines are ___? if their limbs has approximately equal dips
Symmetrical
A fault in which the axial plane has been overtuned
Recumbent fold
circular or elliptical structural or topographic highs in which beds dip away to all directions; when eroded, the oldest rocks are exposed at the center
Domes
circular or elliptical structural or topographic lows or down warps in which beds dip towards the center; when eroded, the youngest rocks are exposed at the center
Basins
A giant landmass called?
Pangaea
Pangaea means?
All land
When all continents were joined to form pangaea, rest of the earth’s surface is covered by a huge ocean called_________
Panthalassa
theory that the outer rigid layer of the earth (the lithosphere) is divided into a couple of dozen “plates” that move around across the earth’s surface relative to each other, like slabs of ice on a lake
Plate tectonics theory
Seven major and minor plates:
