plate tectonics Flashcards
who discovered the continental drift theory
alfred wegner
what is the continental drift theory
all continents had originally been one big continent and began to break apart into the continents we have today
what is the one big continent called (consisted of the continents we have today)
pangaea
what are the evidences for the continental drift theory (4 evidences)
puzzle like fit
rock formations
matching fossils
climate evidence
a small reptile, couldnt have crossed the ocean yet its fossils were in south america and africa, proof of matching fossils
mesosaurus
a land plant found in africa, south america, australia etc. can be proof of matching fossils
glossopteris
how does climate evidence supporting the continental drift theory
glaciers near the equator - striations and deposits found in southern Africa and South America
what two reasons rejected the continental drift theory
wegner couldn’t find why the continents moved
where do earthquakes and volcanoes occur
plate boundaries
what is a plate boundary
2 plates are either pushing away, pulling away, or sliding against each other
how do earthquakes occur (strain, fractures)
strain builds up along boundaries and when it becomes too much fractures form and earthquakes occur
how do volcanoes form (heat, molten rock)
boundaries have a lot of heat flow, where molten rock moves up to the surface
what is a magnetic field (of earth)
invisibles lines of force that pass through earth from one pole to another
what does earths magnetic field do once and a while (hint: a compass would point to the south during this)
reversal
what is paleomagnetism and what was it used for
natural magnetism in rocks, determine locations of magnetic poles in rock
how did paleomagnetism help with evidence for seafloor spreading
discovery of strips of alternating polarity in rock
what is seafloor spreading
tectonic plates separating from each other and making new ocean floor material
where does seafloor spreading occur
mid-ocean ridges
seafloor spreading spreads about __ cm per year, rock and sediment are youngest near the _____ oldest near the _______
5, ridge, trenches
what are the layers of the earth from outer to inner (4 layers)
crust, mantle, outer core, inner core
what is the lithosphere
rigid part, made of crust and mantle
what is the asthenosphere
under lithosphere, made of upper mantle, plates move around on top of asthenosphere
divergent boundary
two plates move apart
convergent boundary
two plates collide into each other
subduction zone
one oceanic plate is forced under another plate
what are the three types of convergent boundaries
ocean-continental
ocean-ocean
continental-continental
describe ocean-continental boundary and what it makes
less dense, plates float above and more dense ocean plates sink, forms volcanoes
describe ocean-ocean boundary and what it makes
one ocean plate subducts under another plate, forms volcanic islands
describe continental-continental boundary and what it makes
floats since lithosphere can’t be subducted, forms mountain ranges
transform boundary
2 plates slide past each other horizontally, sliding motion can cause earthquakes
where do mountains form
long belts near convergent plate boundaries, continental margin boundary (between ocean and cont. crust)
what affects rocks at convergent boundaries
stress
what are the 3 types of stress and define them
compression- squeezed inward
tension- stretched
shear- pushed in opposite directions
during plate collision stress can cause rock layers to bend into ______
folds
break in lithosphere where movement has occurred
fault
what are the three types of faults and define each of them
normal- hanging wall moves down relative to footwall
reverse- handing wall move up relative to footwall
strike-slip- rocks on opposite sides of fault horizontally
what is an earthquake
movement in ground caused by sudden rocks moving along a fault
focus
location under earth’s surface where rocks begin to move or break
epicenter
point on earth’s surface directly above the focus
waves that travel from inside the earth
body waves
primary - travel through solids and liquids, fastest seismic waves, back-and-forth motion
p waves
secondary waves, travel only through solids, fast moving not as fast as p waves, side to side movement
s waves
waves that travel along earths surface, move slowly, cause most damage
surface waves
cause ground to move in a side to side motion
love wave
particles of material move in circular patterns
rayleigh waves
what tool is used to record waves made by an earthquake
seismograph
the sheet a seismograph prints out and determines strength and location is called what
seismogram
measure of amount of energy released
magnitude
scale used to measure strength of earthquakes
richter scale
scale used to measure amount of earthquake damage
modified mercalli
large earthquakes followed by small rippling ones this is called
aftershocks
movement of magma on earth
volcanism
vent that magma and gases come out is a
volcano
areas of volcanism that dont occur along plate boundaries
hot spots
solid hot material from deep in mantle rises and reaches lithosphere
mantle plumes
plume spreads out and magma breaks into surface forming…
hot spot volcanoes
