final Flashcards
determining the actual age of a rock
aka radiometric dating
relies on radioactivity of element isotopes
absolute dating
what does a radioactive atom give off
energy, radiation, particle
isotope nucleus undergoes changes
decay
the time it takes for half of the sample to undergo radioactive decay
half life
what are the three types of decay
alpha, beta, gamma
nucleus loses an He nucleus
radiation can be stopped by paper
example radon gas dangerous when inhaled
alpha decay
loses an electron from the nucleus
neutron becomes a proton
wood blocks radiation
beta decay minus
nucleus gains an electron
proton becomes a neutron
beta plus
loss of He nucles minus 2 atomic number
Alpha
neutron becomes proton plus 1 atomic number
beta minus
proton becomes neutron minus 1 atomic number
beta plus
no mass lost, no change in element
gamma
U238 –> Pb 206
4.5 billion years
Rb87–>Sr87
47 billion years
K40–> Ar40
1.3 billion years
C14 –> N14 5730
5730
fold of rocks with younger rock layers closer to the center of the structure
syncline
what shape does a syncline make
u
what is the shape of an anticline
an A (upside down u)
what is the age of the rock on the inside of the syncline
young in the center- gets older as it moves outward
what is the age of the rock on the inside of the anticline
old in the center- gets younger as it moves outward
structural trap formed by the folding of rock strata into an arch-like shape
anticline
an area of relatively level high ground.
plateau
who is the father of modern geology
james hurton
what idea did james hurton come up with
uniformitarianism
the present is the key to the past
uniformitarianism
placing rock in sequence
relative dating
undeformed sequence of sedimentary rock
entrusive igneous rock
oldest at the bottom
youngest at the top
law of superposition
layers of sedimentary rocks are generally deposited in a horizontal fashion
law of original horizontality
how do you determine which way is up?
find mud cracks that curl upwards
ripples that look like a current (asymmetrical)
current ripples
symmetrical ripples
oscillation
fault or intrusions must be younger than the rock they intersect
principle of crosscutting relationships
missing portions of rock record (missing time)
caused by erosions or lack of rock-forming environments
law of unconformity
fossil organisms succeed one another in a definite and determinable order
time periods can be recognized by fossil type
principle of faunal succession
use to define/identity geologic periods
-easy to identify
-broad distribution
-short-lived
index fossils
