Plate Tectonics Flashcards
suggests that all the continents were
joined into a single large landmass called
supercontinent Pangaea
Continental Drift Theory
he introduced the continental drift theory
Alfred Wegener
name of the ocean surrounding Pangaea
Panthalassa
~180 My, it broke off into two large masses called
Laurasia and Gondwana
w/ Tethys sea in between
4 continental drift theory proofs
jigsaw fit
index fossils
rock types among continents
paleoclimate evidences
suggests that the seafloor moves and carries the crust with it as it
spreads from a central rift axis (oceanic ridge)
seafloor spreading
he proposed seafloor spreading
Harry Hammond Hess (1962)
name of his proposal/theory
geopoetry
the record of the earth
magnetic field through time in rocks
paleomagnetism
material from the mantle that rises up through the mid-ocean ridge is basalt
that contains magnetite – a rock mineral that is highly magnetic and aligns with the magnetic field
Vine-Matthews-Morley Hypothesis
unifying theory of geology
Plate Tectonics Theory (1968)
Major Plates of the Lithosphere (7)
Eurasia, North America, Australia, Pacific, South America, Africa, and Antarctic
Small plates in the lithosphere
Philippine sea plate, Cocos, Juan de Fuca, Caribbean, Nazca, Scotia
created crustal material in divergent boundaries
mafic igneous rock, Basalt or Gabbro
formed when the ridge opens up and a column of magma cools in the
crack. This column is cracked again in the middle due to spreading and is intruded by a new dyke. It can be thought of as a dyke within a dyke
within a dyke (so on and so forth)
Sheeted dykes
formed when lava oozes out into the water. The lava cools quickly on the outside since it is in contact with water, allowing a “shell” to form. Pressure is built up inside and it breaks the shell, allowing magma to ooze out again, repeating the process
Pillow Lavas
Since Oceanic crust/plate is denser the continental crust/plate, oceanic
crust/plate subducts underneath continental crust.
Oceanic-continental convergent boundary
▪ Since both are quite dense, one of them subducts (older and colder plate = denser) and usually forms an ocean
trench
Oceanic-oceanic convergent boundary
Happens when the plate has moved so much that continental part of it becomes the one converging with another
continental material.
continental-continental convergent boundary
Accumulated sediment on continental slope is thrust up and
forms
accretionary wedge
Plates slides across each other without creation or destruction of crustal material.
transform boundary
convection cells in asthenosphere
mantle convection/traction
upwelling of mantle causes newer and warmer material
to form that will in turn be pushing older and colder material away
from the ridge.
ridge push
older and colder plate segments at subduction zones become colder and denser thus goes down further and pulls the rest of the plate attached to it
slab pull
plates that move the fastest
plates with subducting parts
3 magma forming plate-tectonic settings
divergent - decompression melting
convergent - flux melting
mantle plume - heat induced melting
melting or partial melting of hot rock as pressure on it is reduced
decompression melting
Mantle material is melted by simply adding heat
heat-induced melting
When subducting plate material is heated, it may force water out of the
minerals (heat is not enough to cause melting). The water rises into the rock above it and wets it. Being wet causes partial melting of the rock
flux melting
Spot where hot mantle material goes up through the crust and up above the surface
mantle plume
elongation/stretching of the crust in some
areas resulting to its thinning. Since it is
thin, it allows rising of mantle material
continental rifting
Regular fracture surfaces of rock masses, usually planar, cutting across the rock at constant orientation and spacing
joints
Occurs when plates collide or shear past each other, when intrusions are emplaced, when uplift or subsidence occurs or when earth is stress at specific points
rock deformation
Produced from bending of rock strata without rupture
folds
Crustal rock failure by shear rupture
faults
3 types of faults
dip-slip faults (normal and reverse)
strike-slip faults
Faults whose movement is parallel to the
dip of the fault
dip-slip faults
– the rocks are pulled
apart (extension)
normal fault
– the rocks are pushed
together (compression)
reverse fault
Faults whose movement is along the strike or length of fault
strike-slip fault
– rifted from mainland Asia starting 33 Mya.
Includes Palawan and some Panay islands.
It existed before PMB and contains the oldest rocks in the country.
Palawan continental block
collision of Sunda Plate, Philippine Sea Plate, and
Indo-Australian Plate. Most parts of the PH
belongs here.
Philippine mobile belt
the country’s
longest fault that traverses the entire length of the archipelago. It is a left-lateral fault.
Philippine fault
how many active volcanoes in the Philippines
24
