Geologic Time and History PPT

Question 1

catastrophism

Answer 1

large scale geologic features formed in catastrophic events; the age of the earth can be measured in human historical terms; fast process over short time (ex: island formation, volcanic eruption)

Question 2

uniformitarianism

Answer 2

earth processes can be observed to understand the past; the Earth was ancient much beyond the span of human history; slow process over wide geologic time; older than human lived (ex: sediment deposition, evolution)

Question 3

stratigraphy

Answer 3

the science of rock layers and the processes by which they are formed (stratum is a layer of sedimentary rocks)

Question 4

relative age rocks

Answer 4

sequence of past geologic events; age of rock, fossil, or other geologic feature relative to another feature; order of the events are analyzed but not the actual numerical age

Question 5

what can complicate the relative age of rocks

Answer 5

dykes, faults, folds

Question 6

name the four principles

Answer 6

original horizontality, stratigraphic superposition, lateral continuity, cross-cutting relationship

Question 7

principle of original horizontality

Answer 7

water-laid sediments are deposited in horizontal strata (horizontal is key here)

Question 8

principle of stratigraphic superposition

Answer 8

in undisturbed sequence of strata, each stratum is younger than the stratum below it and older than the stratum above it

Question 9

principle of lateral continuity

Answer 9

sediments deposited in continuous layers (meaning that, if a valley cuts through a piece of land, they rocks will still stay horizontal with each other)

Question 10

principle of cross cutting relationship

Answer 10

stratum must be older than any feature that cuts or disrupts it (dyke, fold, fault)

Question 11

correlation

Answer 11

a method of equating the ages of strata that come from two or more different places

Question 12

index fossils

Answer 12

fossils that lived in short period, have a wide geographic range (ex: trilobite)

Question 13

fossils

Answer 13

remains or traces of prehistoric life; can be plants or animals; important inclusions in sediment and sedimentary rocks; important tool to interpret the geologic past; paleontology is the study of fossils; contribute to the geometric fit theory with plate tectonics

Question 14

geologic time scale

Answer 14

a system of chronological measurement that relates stratigraphy to time (eon, ara, period, epoch)

Question 15

Eons

Answer 15

Hadean, archean, proterozoic, phanerozoic

Question 16

hadean

Answer 16

time between earth’s creation and age of the oldest rocks discovered

Question 17

archean

Answer 17

roughly when single-celled life developed

Question 18

proterozoic

Answer 18

multi-celled, soft-bodied organisms emerged

Question 19

phanerozoic

Answer 19

the current eon where “visible life” is abundant

Question 20

phanerozoic is divided into…

Answer 20

eras

Question 21

eras

Answer 21

paleozoic, mesozoic, cenozoic

Question 22

paleozoic

Answer 22

fish, amphibians, and reptiles

Question 23

mesozoic

Answer 23

dinosaurs and flowering plants

Question 24

cenozoic

Answer 24

birds, mammals, primates, humans

Question 25

isotope

Answer 25

atom of the same element with the same atomic number but different mass number

Question 26

stable vs. radiogenic isotopes

Answer 26

radiogenic isotopes: amount of element decreases with time

Question 27

radioactivity

Answer 27

process in which an element spontaneously transforms; end product is either another isotope of the same element or into a different element (carbon14, potassium40, uranium, thorium, lead); rate of decay is constant

Question 28

t-half life

Answer 28

time needed for half of the parent atom of a radioactive substance to decay into daughter atoms (longer half-life to date older rocks and vice versa)

Question 29

to find the numerical age, scientists generally turn to…

Answer 29

radioactivity