geologic history

Question 1

what does an unconformity represent

Answer 1

time gap in the record of the area

Question 2

why are ancient volcanic ash deposits important to geologists

Answer 2

the serve as good geologic time markers

Question 3

living corals are found in warm shallow seas. coral fossils are found in the sedimentary rocks of Alaska. what does this suggest?

Answer 3

Alaska once had a tropical marine environment

Question 4

unless a series of sedimentary rock layers is overturned the bottom layer is usually…

Answer 4

older

Question 5

which feature in a rock layer is older than the rock layer

Answer 5

rock fragments

Question 6

the fossil record indicates that most plants and animals that lived on Earth in the past….

Answer 6

have been extinct

Question 7

what are two ways to date rocks

Answer 7

relative age
absolute age

Question 8

relative age example

Answer 8

correlation

Question 9

principle of superposition

Answer 9

sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below it

Question 10

unconformity

Answer 10

buried erosion surface separating two rock masses or strata of different ages

Question 11

what does unconformity indicate

Answer 11

sediment deposition was not continuous

Question 12

correlation

Answer 12

rocks or geology events from different places are determined to be the same age or similar

Question 13

3 methods of correlation

Answer 13

similarities in rocks
index fossils
volcanic ash/ meteorite deposits

Question 14

what are some characteristics of an index fossil

Answer 14

large horizontal distribution
small vertical distribution

Question 15

horizontal distribution

Answer 15

how big the fossil’s geographic range is

Question 16

vertical distribution

Answer 16

how long it lived

Question 17

what does all matter in the universe contain

Answer 17

atoms

Question 18

Atomic number

Answer 18

the number of protons

Question 19

mass number

Answer 19

number of protons and neutrons

Question 20

isotopes

Answer 20

elements that have differing mass numbers

Question 21

what is an example of an isotope

Answer 21

c-12 contains 6 protons and 6 neutrons

Question 22

what is the mass number of c-24

Answer 22

12 protons and 12 neutrons

Question 23

are isotopes radioactive

Answer 23

yes

Question 24

do heat and pressure affect isotopes

Answer 24

no

Question 25

half-life

Answer 25

time it takes for a radioactive parent isotope to decay by 1/2

Question 26

how long can carbon-14 date back to

Answer 26

50-70,000 years

Question 27

how many years does the geologic time scale cover

Answer 27

4.6 billion years

Question 28

list categories of geologic time scale from big to small

Answer 28

eon era period epoch