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