chapter 12
James Hutton
"The present is the key to the past"
Principle of cross-cutting relationships
"the cutter is younger than the cuttee" - rock layers are older than the fault - fault/magma that is cutting is newer than the rock layers
epoch
(n.) a distinct period of time, era, age
Carbon 14 half life
5730 years (turns to carbon-12)
Precambrian Time
88% of geologic time and is first of these eons (Haden, Archaen, and Proterozoic)
deep time
Earth has an indefinitely long history
Charles Darwin
English natural scientist who formulated a theory of evolution by natural selection (1809-1882)
Principle of fossil succession
Fossil organisms succeed one another in a definite and determinable order, and any time period can be recognized by its fossil content.
eras
Paleozoic, Mesozoic, Cenozoic
possession of hard parts
Shells, bones and teeth are more likely to be preserved than fleshy material
Uniformaitarism
Those processes that have governed the earth in the past, are governing the earth now and will do so in the future
earth is old, and the same processes occurring now happened in the past (helps geologists decode the past)
What do rock records tell us
index fossil
a fossil that is geographically wide-spread and abundant, yet lived for a limited time
Unaltered remains
actually unaltered remains preserved in ice, amber, or tar
Principle of original horizontality
all rocks when originally formed, formed horizontally
half-life
amount of time for one half of the nuclei in radioactive isotope to decay to a stable isotope
impression
an imprint (without any organic matter, does show details though)
Angular unconformity
angular rocks on top of flat rocks Newer rock layers that are horizontal on top of older angular rocks it means something is off
rock/mineral absolute age
approximate number of years before present that is formed
Proterozoic
before animal
adaptations
beneficial inherited traits that are passed to future generations
compression
called carbon films and have organic matter (carbon weeps out)
radiocarbon dating
date organics with carbon-14
periods
differ in geologic events, environmental conditions, and life forms
Paleozoic Era
eras in the Phanerozic
foot prints, burrows, coprolites (poop), gastroliths (stomach stones)
examples of trace fossils
principle of fossil succession
fossil organisms tend to be found in the same general order at different locations
Disconformity
gap in the rock record - two sedimentary layers separated by an erosion surface
radiometric decay rates are constant
how do scientists know that an isotope is reliable
when an organism dies, the amount of carbon-14 decrease. By comparing the carbon-14 to the carbon-12 (stable), radiocarbon dates are found
how is carbon-14 used in radioactive dating
4.6 (or 4.5) billion years old
how old is the earth
mold
is a hollow representation of it
geological time scale
is a record that includes both geologic events and major developments in the evolution of life
cast
is a soil representation (carbon film)
eon
longest interval of geologic time
radiometric dating
method of calculating the absolute ages of rocks and minerals that contain certain radioactive isotopes
Mesozoic Era
middle animal (dinos)
Cenpzoic
new animal (mammals)
Paleozoic
old animal/ancient life
Law of superposition
oldest rock layers (undisturbed) are found on the bottom
Inclusion
pieces of one rock unit that are contained within another rock unit
Relative age
placing events in order that they happened without assigning an actual year
fossils
preserved remains or traces of an organism
Correlation
process of matching up rock layers over a great distance
rapid burial
protects from oxygen (bacteria) and scavengers
Absolute age
put things in order and assigns a specific year
Relative dating and time
relative dating gives us the sequence but not when (date) it happened
Unstable atomic nuclei
spontaneously break apart, or decay releasing energy
Unconformities(not normal)
surface that represents a break in the rock record
daughter
the isotopes resulting from the decay of a parent
Radioactivity
the process by which atoms decay
natural selection
theory that traits improve an individuals chance for survival and reproduction will be passed down with good traits
Petrified fossil
turned to stone - soft tissue from organism actually becomes rock
Nonconformity
two different types of rock each other
parent
unstable radioactive isotope
thanerozoic
visible animal
rapid burial and possession of hard parts
what conditions favor fossil preservation
relating to igneous rocks
what do scientists use to measure sedimentary rocks
Sedimentary
what rocks can have fossils
organisms that are well-adapted to their environment (due to evolution) are more likely to survive compared to those who are not
why do organisms evolve
