Chapter 3 (part 1)

Question 1

The science that deals with determining the ages of rocks is called ____

Answer 1

Geochronology

Question 2

____ uses fundamental principles of geology (Steno’s Laws, Fossil Succession, etc.) to determine the relative ages of rocks (which rocks are older andwhich are younger).

Answer 2

Relative Dating

Question 3

____ quantifies the date of the rock in years. This is done primarily by radiometric dating (or analysis of the breakdown of radioactive elements in the rocks over time).

Answer 3

Absolute Dating

Question 4

____ Has been determined bit-by-bit over the years through relative dating, correlation, examiniation of fossils and radiometric dating

Answer 4

The Geologic Time Scale

Question 5

____ are the largest division of geologic time.

Answer 5

Eons

Question 6

The Precambrian covers ____ of geologic history.

Answer 6

87%

Question 7

There are three ____ in the Phanerozoic Eon & are divided into geologic periods.

Answer 7

Eras

Question 8

Eras are divided into ____

Answer 8

Periods

Question 9

Periods can be subdivided into ____

Answer 9

Epochs

Question 10

Epochs can be subdivided into ____

Answer 10

Ages

Question 11

____ are the actual rocks formed or deposited during a specific time interval. They are sometimes called time-rock units.

Answer 11

Chronostratigraphic Units

Question 12

The Archean and Proterozoic are together referred to as the ____ , meaning “before the Cambrian Period”.

Answer 12

Precambrian

Question 13

The ____ is the smallest particle of matter that can exist as a chemical element.

Answer 13

Atom

Question 14

If there is an unequal number of protons and electrons, the atom has a charge (positive or negative), and it is called an ____

Answer 14

Ion

Question 15

The ____ of an atom = number of protons in the nucleus of that atom.

Answer 15

Atomic Number

Question 16

The atomic number of uranium is ___

Answer 16

92

Question 17

The ____ is the sum of the number of protons plus neutrons.

Answer 17

Mass Number

Question 18

Uranium-235 has 92 protons and ____ neutrons.

Answer 18

143

Question 19

The mass number may vary for an element, because of a differing number of ____

Answer 19

neutrons

Question 20

Elements with various numbers of neutrons are called ____ of that element.

Answer 20

Isotopes

Question 21

As ____ decays to lead, there are 13 intermediate radioactive daughter products formed (including radon, polonium, and other isotopes of uranium), along with and 8 alpha particles and 6 beta particles released.

Answer 21

Uranium-238

Question 22

____ particles are large, easily stopped by papercharge = +2 mass = 4

Answer 22

Alpha

Question 23

____ particles - penetrate hundreds of times farther than alpha particles, but easily stopped compared with neutrons and gamma rays.charge = -1 mass = negligible

Answer 23

Beta

Question 24

____ are highly penetrating no charge mass = 1

Answer 24

Neutrons

Question 25

____ are highly penetrating electromagnetic radiation which can penetrate concrete. Lead shield can be used. Photons (light). no charge no mass.

Answer 25

Gamma rays

high energy x-rays

Question 26

Naturally-occurring radioactive materials break down into other materials at known rates.This is known as ____ decay.

Answer 26

Radioactive

Question 27

Many radioactive elements can be used as geologic clocks because each radioactive element ____ at its own constant rate.

Answer 27

Decays

Question 28

Geologists can estimate the length of time over which decay has been occurring by can be found by measuring the amount of radioactive parent element and the amount of stable ____

Answer 28

Daughter Elements

Question 29

The quantities and masses of atoms and isotopes are measured using an instrument called a ____

Answer 29

Mass Spectrometer

Question 30

The mass spectrometer came into use after ____

Answer 30

WWI (1918)

Question 31

The mass spectrometer led to the discovery of more than ____ isotopes.

Answer 31

200

Question 32

Radioactive decay occurs at a constant ____ or geometric rate.

Answer 32

Exponential

Question 33

The rate of decay is proportional to the number of ____ atoms present.

Answer 33

Parent

Question 34

Each radioactive isotope has its own unique ____

Answer 34

Half-Life

Question 35

A half-life is the time it takes for half of the parent radioactive element to decay to a ____

Answer 35

Daughter Product

Question 36

What rocks are best for age dating?

Answer 36

Igneous Rocks

(the dates they give tell when the magma cooled- when the magma cools and crystallized containing some radioactive elements that can be dated.)

Question 37

The ages of sedimentary rocks and fossils are determined using ____

Answer 37

Both Relative & Absolute Dating

Question 38

The ages of fossils in a sequence of sedimentary rocks can be determined using ____

Answer 38

Both Relative & Absolute Dating

Question 39

Cosmic rays from the sun strike nitrogen-14 atoms in the atmosphere and cause them to turn into radioactive carbon-14, which combines with oxygen to form ____

Answer 39

Radioactive Carbon Dioxide

Question 40

Living things are in equilibrium with the atmosphere, and the radioactive carbon dioxide is absorbed and used by____. The radioactive carbon dioxide gets into the food chain and the carbon cycle.

Answer 40

Plants

Question 41

All living things contain a constant ratio of ____

Answer 41

Carbon-14 to Carbon-12.

1 in a trillion

Question 42

What is the basis for Carbon-14 dating?

Answer 42

The Change In Carbon-14 to Carbon-12 Ratio

Question 43

Carbon-14 dating can only be used on materials less than ____. Assuming that the rate of carbon-14 production has been constant.

Answer 43

70,000 years old

Question 44

Charged particles from radioactive decay pass through mineral’s crystal lattice and leave trails of damage called ____

Answer 44

Fission Tracks

Question 45

____ looks at the number of tracks per unit area is a function of age and uranium concentration.

Answer 45

Fission Track Dating

Question 46

The oldest rocks that have been dated are ____. They date from the time of the origin of the solar system and the Earth, about 4.6 billion years old.

Answer 46

Meteorites

Question 47

The oldest Moon rocks are from the ____, and may represent the original lunar crust.

Answer 47

Lunar Highlands

the ighter-colored areas on the moon

Question 48

The oldest dates of Earth rocks are ____ detrital zircon grains in a sandstone in western Australia.

Answer 48

4.2 Billion Years Old