Geology Test 2

Front 1

Relative Dating

Back 1

defined by the law of superposition.

Front 2

superposition

Back 2

oldest rocks are on the bottom. developed by Nicolaus Steno in 1669

Front 3

actual dating

Back 3

uses radioactive dating and it is getting the actual date of a rock

Front 4

What is the age of the oldes rock ever dated?

Back 4

3.9 billion years ago

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What is the age of the 1st fossilized life

Back 5

3.5 billion years ago

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What are the 4 Eons

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Phanerozoic, Proterozoic, Archean, Hadean

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What are the 3 Era's in the Phanerozoic Era

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Cenozoic, Mesozoic, Paleozoic,

Front 8

Precambian Eon

Back 8

includes anything before Cambrian. It includes 88% of the 4.6 billion years of the age of Earth.

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Phanerozoic

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visible life. LIfe became very evident. most recent eon and began about 540 million years ago

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Proterozoic

Back 10

very primitive. 3rd to oldest.

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Archean

Back 11

2nd to oldest Eon

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Hadean

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oldest Eon

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Eon

Back 13

greatest expanse of time

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Era

Back 14

subdivision of an eon

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Cenozoic

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Era of recent life

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Mesozoic

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Era of middle life

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Paleozoic

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Era of ancient life

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Order of divisions

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Eon-Era-Period-Epochs

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What is the geological time scale

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a calendar of Earth History

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How was the geological time scale originally created?

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using relative dates, but now days we use radiometric dating.

Front 21

anything that happenned before the cambrian period is called

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Precambrian

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Principal of original horizontality

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Used in Relative dating. rock layers that are flat have not been disturbed. This concept holds true because layers that are flat have not been disturbed.

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Principal of cross-cutting

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Used in Relative dating. younger features cut across older feature. New matter cutting through a rock is younger because what it cut through is there first..

Front 24

Inclusion

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Used in Relative Dating. an inclusion is a piece of rock that is enclosed within another rock. Rock containing the inclusion is younger. An example of this is when lava flows and picks up rocks while cooling.

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Unconformity

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Used in Relative Dating. a varied surface of erosion. rocks are exposed on surface of Earth and then buried. important Because shows when events happenned.

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What are the 3 types of unconformity

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angular, disconformity, and nonconformity

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angular

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tilted rocks are overlain by flat-lying rocks. (tilted)

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disconformity

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strata on either side of the unconformity are parallel. (parrallel)

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nonconformity

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metamorphic or igneous rocks in contact with sedimentary strata. (metamorphic or igneous)

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How to tell what kind of unconformity.

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the rock is buried due to erosion. look above and below to determine type of erosion.

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fossil

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traces (can include poop or footprints) or remains of prehistoric life now preserved in rock.

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where are fossils generally found?

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sediment or sedimentary rocks. Rarely in metamorphic and almost never in igneous rock.

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Paleontology

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study of fossils

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copperlite

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fossilized poop

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What is the only direct evidence of past life?

Back 35

fossils

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Do fossils help determine the age of some rocks?

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yes, because a rock can be dated by dating the age of the fossil in it.

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Geologically fossils are important because they

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a. aid in interpretation of the geological past
b. serve as important time indicators
c. allow for correlation of rocks from different places.

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Types of fossils

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a. the remains of relatively recent organisms- including teeth, bones, etC
b. entire animal, flesh included. this is rare but can happen in sap, or glaciers
c. given enough time, remains may be petrified(turned to stone)
d. molds and casts
e. carbonization

Front 39

Other types of fossils

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tracks, burrows (from organism digging, coprolites (fossil dung), Gastroliths (polished stomach stone)

Front 40

what conditions favor preservation

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rapid burial (often in lakes and oceans)
possession of hard parts (skeleton, shell, etc.)

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animites

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octopus like animals. not actually shell but mud made cast of shells.

Front 42

correlation

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matching of rocks of similar ages in different regions

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What does correlation often rely on?

Back 43

fossils

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Who noted that sedimentary strata in widely separated area could be identified and correlated by thier distinctive fossil content

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William Smith in late 1700's

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principal of fossil succession

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fossil organisms succeed one another in a definite and determinable order, and therefore any time period can be recognized by its fossil content.

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index fossil

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geographically widespread fossil that is limited to a short span of geological time.

Front 47

Dating with radioactivity includes knowing what structure?

Back 47

basic atomic structure

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what does the basic atomic structure include

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Nucleus, Atomic Number, Mass Number, and Isotope

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Nucleus includes

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Protons, Neutrons, and Electrons

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Protons

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charged particles with mass

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Neutrons

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neutral particles with mass

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Electrons

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charged particles that orbit the nucleus

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Atomic number

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Element's identifying number, and in the nucleus there is an equal number of protons.

Front 54

Mass number

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Sum of the number of protons and neutrons.

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Isotope

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variant of the same paretn atom, differs in the number of neutrons, results in a different mass number than the parent atom. Same atom wtih different types of neutrons gives types of mass #'s.

Front 56

radioactivity

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spontaneous changes (decay) in the structure of atomic nuclei.

Front 57

types of radioactive decay

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alpha, beta, electron

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alpha emission

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can stop with piece of paper. Emission of 2 protons and 2 neutrons. Mass number is reduced by 4 and the atomic number is lowered by 2.

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beta emission

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wood could stop. an electorn is ejected from the nucleus. mass number remains unchanged and the atomic number increases by 1

Front 60

electron capture

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an electron is captured by the nucleus and combines with a proton to form a neutron. Mass number remains unchanged and atomic number decreases by 1

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Parent

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dealing with radioactivity. an unstable radioactive isotope.

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Daughter Product

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the isotopes resulting from the decay of a parent.

Front 63

Half-life

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the time required for one-half of the radioactive nuclei in a sample to decay.

Front 64

radiometric dating

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the percentage of radioactive atoms that decay during one half-life is always the same (50%).
However, the actual number of atoms that decay continually decreases.
Comparing the ratio of parent to daughter yields the age of the sample.

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theoretically should there be something left at end of radioactive decay curve?

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yes, because everything measured in half-life.

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What are sources of error in radiometric dating.

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A. a closed system is required.
B. to avoid potential problems, only fresh, unweathered rock samples should be used

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Radiocarbon dating

Back 67

dating with carbon

Front 68

things involving carbon-14 dating

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half life= 5730 years
used to date very recent events
carbon 14 is produced in the upper atmosphere
useful tool for anthropologists, archeologists, and geologists who study very recent Earth History.

Front 69

Draw backs to carbon-14 dating

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can only be used on things that were once alive.
has limits because if too old too broken down to c14 date.

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importance of radiometric dating

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A. radiometric dating is a complex procedure that requires precise measurement.
B. Rocks from several localities have been dated at more than 3 billion years.
C. Confirms the idea that geologic time is immense.

Front 71

Precambrian time

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A. nearly 4 billion years prior to the Cambrian period.
B. Not divided into smaller time units because the events of Precambrian history are not known in great enough detail.
C. the first abundant fossil evidence does not appear until the beginning of the Cambrian

Front 72

Difficulties in dating the geological time scale.

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Not all rocks can be dated by radiometic methods because:
A. grains comprising detrial sedimentary rocks are not the sme age as the rock in which they formed.
B. The age of a particular mineral in a metamorphic rock may not neccessarily represent the time when the rock formed.
C. Datable materials (such as volcanic ash beds and igneous intrusions) are often used to bracket various episodes in Earth history and arrive at ages.

Front 73

Even though every rock cannot be dated you can get an idea of age by

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looking above and below the rock

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What eon and era are we living in?

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Phanerozoic Eon and Cenozoic Era.