exam 1 Flashcards
Original horizontality
the way sediment is laid down, they should be close to horizontal –> If they aren’t, horizontal, they shifted
Superposition
when laying down sedimentary layers, older layers @ bottom, younger layers @ top
Cross-cutting relationships
if something cuts across existing layers (ex: fault), it has to come after the layers it cuts through
Radiometric dating
rocks could be dated based on decay of radioactive material
(Uses naturally radioactive isotopes)
Half-life
time it takes an amount of a radioactive isotope to decay to half the amount
after 1 half-life there are __ parent isotopes and __ daughter istopes; this is because of the __ rate.
1/2 parent, 1/2 daughter, constant
pioneer in mapping oceans
Marie Tharp
relative dating
the ORDER in which geological features formed
absolute dating
exact time geological features formed (Ex: radiometric dating)
what elements make up the core?
iron and nickel alloys
what elements make up the mantle?
ultramafic rocks
what elements make up the crust?
felsic to mafic rocks
what components make up felsic rock?
silicon and oxygen
uncomformities
surface b/w two rock layers representing a missing layer that was either never formed or eroded away (missing rock record)
what components make up mafic rock?
magnesium and iron
what layers make up the lithosphere?
crust and upper mantle
how rigid is the lithosphere?
rigid
what layers make up the asthenosphere?
remaining upper mantle (from lithosphere)
how rigid is the asthenosphere?
semi-ductile but solid
what layers make up the mesosphere?
lower mantle
how rigid is the mesosphere?
rigid
what phase is the outer core?
liquid
what phase is the inner core?
solid
angular uncomformity
tectonic forces causing compression and uplift
why do seismic waves propagate?
elasticity of earth
what does P-wave stand for?
pressure (compression) or primary wave
what is the fastest wave?
p-wave
what direction does p-wave go in?
parallel
what is the s-wave?
sheer or secondary
which is the slower wave?
s-wave
what direction do s-waves go?
perpendicular
wavefront
line connecting peaks and troughs
ray
perpendicular path to wavefront that points in direction of wave propagation
refraction
waves create bent paths due to varying speeds
examples of geosystems
climate, plate tectonics, geodynamics
Geologic record
info preserved in rocks formed throughout history
Hutton’s original theory of uniformitarianism:
- Earth’s processes are slow + Time is recorded in rocks = great changes are accomplished over large periods of time
- Earth = old
- Geologic processes occur at CONSTANT rate of long periods of time
Modern Theory of uniformitarianism:
Principles of geologic time remain constant, but rates and intensities VARY
geodesy
study of earth’s shape and surface
what was the shape of earth according to ancient greece vs. today?
- spherical
- not perfect sphere
examples of isotope dating methods
uranium-lead, potassium-argon, rubidium-strontium, carbon-nitrogen
earth’s topography ranges ___ , we know because of __
20 km; surface elevation
nebular hypothesis
formation of solar system
which planets are closest to the sun?
heavier planets
Which is thicker: continental or oceanic crust?
Continental is thicker (we know because of changes in elevation)
How do we know earth is layered?
*seismic waves, Isostasy, 2 crusts w/ 2 densities, Trenches in the ocean (sea floor spreading)
order of layers of earth
solid iron inner core –> liquid iron outer core –> mantle –> crust
the largest layer of earth’s mass =
mantle
isostasy
equilibrium b/w forces of GRAVITY pulling down and BUOYANCY pushing surface up
Why do continents ride higher on underlying mantle than oceans?
- Difference in densities and buoyancy
- Upper mantle is ductile
which is denser: continental or oceanic crust?
ocean crust = denser than continental
why to continents float?
difference in density; continental crust is made up of lighter rock than the higher density oceanic rock
which is thicker: continental or oceanic crust?
continental
What causes the lithosphere to be more rigid than the asthenosphere?
the lithosphere is at a lower temp than the asthenosphere
What causes abrupt changes in density between earth’s major interior layers?
Chemical composition of those layers
what drives the magnetism of earths core?
heat inside the core
where can s-waves not travel?
the outer core; 3000-5000 km (depth)
can the p-waves make it through the core?
yes, but they are refracted
how do we know there is a liquid outer core?
the s-waves can’t travel through it and the p-waves are refracted
how might a geochronologist determine how old rocks are?
radio-metric dating, fossilization, super-position, original horizontality
mechanical properties of crust
rigid and solid
mechanical properties of mantle
solid and ductile
mechanical properties of outer core
liquid and ductile
mechanical properties of inner core
solid and rigid
what materials can p-waves travel through?
solids and liquids
what materials can s-waves travel through?
only solids
how does the speed of seismic waves change in the deep interior of earth?
the speed increases with increasing depth/pressure
what influences speed of seismic waves?
density and elasticity of the material its traveling through
