geologic time - exam 2

Question 1

what did scientists use to determine earth’s age before a geologic time scale with numerical dates was established?

Answer 1

a time scale using relative dating principles

Question 2

what development in dating techniques assisted in geologists assigning very accurate dates to earth’s events?

Answer 2

development of radiometric dating techniques

Question 3

numerical dates/ numerical dating means

Answer 3

a specification of the amount of years that have passed since an event has occurred

Question 4

prior to the discovery of ______, geologists had no reliable method of carrying out numerical dating

Answer 4

radioactivity and radiometric dating

Question 5

when geologists place rocks in their proper sequence of formation, what is established?

Answer 5

relative dating

Question 6

in the eighteenth and nineteenth centuries, the practices of numerical dating were elusive. because of this, geologists at the time developed principles of

Answer 6

relative dating

Question 7

what form of dating cannot tell you how long ago something took place, but indicates what events it preceded or succeeded?

Answer 7

relative dating

Question 8

what dating techniques are often used in conjunction?

Answer 8

relative and numerical dating

Question 9

who was the first geologist to recognize a sequence of historical events in an outcrop of sedimentary rock layers?

Answer 9

nicolas steno

Question 10

what basic principle of relative dating did nicolas steno apply?

Answer 10

the principle of superposition

Question 11

what principle states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below?

Answer 11

the principle of superposition

Question 12

the principle of superposition, although based on layers of sedimentary rock, also applies to other surface deposited materials, such as?

Answer 12

lava flows and beds of ash from volcanic activity/eruptions

Question 13

the principal of original horizontality states?

Answer 13

layers of sediment are generally deposited in a horizontal position

Question 14

what principle states that sedimentary beds originate in continuous layers that extend in all directions until they grade into a different type of sediment or until they thin out at the edge of the basin of deposition?

Answer 14

principle of lateral continuity

Question 15

what principle allows geologists to relate rocks in isolated outcrops?

Answer 15

principle of lateral continuity

Question 16

the principle of cross cutting relationships states?

Answer 16

geologic features that cut through or across rocks must have formed after the rock its cutting through

Question 17

what principle states that the rock mass adjacent to a rock containing inclusions must have been there first, in order to provide the rock fragments?

Answer 17

the principle of intrusions

Question 18

citing the principle of inclusions, how do you date the rock mass containing intrusions?

Answer 18

the rock mass containing the intrusions is younger than its adjacent or surrounding rocks

Question 19

layers of rock that were deposited essentially without interruptions are called

Answer 19

conformable

Question 20

no place on earth has a complete set of

Answer 20

conformable strata

Question 21

the deposition of sediment being interrupted caused breaks in the rock record referred to as

Answer 21

unconformities

Question 22

what represents a long period during which deposition ceased, erosion removed previously formed rocks, and then deposition resumed?

Answer 22

an unconformity

Question 23

what kind of unconformity consists of tilted or folded sedimentary rocks overlain by younger, flatter strata?

Answer 23

an angular unconformity

Question 24

angular conformities indicate what?

Answer 24

during the ceasing of deposition, a deformation of tilting, folding, and erosion, occurred

Question 25

what is a gap in the rock record that represents a period where erosion occurred, rather than deposition, called?

Answer 25

disconformity

Question 26

disconformities represent what?

Answer 26

a period of non deposition and erosion

Question 27

what is represented when younger sedimentary strata overlie older metamorphic or intrusive igneous rocks?

Answer 27

a nonconformity

Question 28

for a nonconformity to develop, there must be a period of

Answer 28

uplift and erosion of underlying rocks