Recitation 4- Dating of Rocks, Fossils, and Geologic events

Question 1

geologic time scale

Answer 1

relative-age calendar of earth’s geologic history. Each time interval correlated with a corresponding set of rocks and fossils

Question 2

four major time units

Answer 2

Eons (longest)
Eras
Periods
Epochs (shortest)

Question 3

index fossil

Answer 3

the shorter amount a time a species has been around, the easier to know how old the geologic formation is where it was found
ex: sharks have been around since permian period. So if shark fossil found, unclear if from Permian or present or anything in between

Question 4

quaternary Period

Answer 4

modern age
First homo fossils
70-100% extant mullusks

Question 5

ice age

Answer 5

pleistocene epoch

ended .0117 million years ago

Question 6

when did the asteroid kills all the dinosaurs

Answer 6

65 million years ago
end of Cretaceous period
and end of Mesozoic era

Question 7

permian extinction

Answer 7

251 million years ago
end of permian period
end of Paleozoic era
destroyed 98% of life

Question 8

Carboniferous period

Answer 8

359- 299 years ago
huge tree boom
where coal comes from

Question 9

when id precambrian era end and cambrian begin

Answer 9

542 million years ago

when life took off

Question 10

paleozoic era

Answer 10

old life

ago of trilobites (those crab-lookin things)

Question 11

mesozoic era

Answer 11

middle life

age of reptiles

Question 12

cenozoic

Answer 12

new life

age of mammals

Question 13

law of original horizontality

Answer 13

sediments are laid down horizontally - gravity

Question 14

law of lateral continuity

Answer 14

beds are being laid down equally everywhere, and continuously
you know that the river started flowing after all the other layers were laid down (if river eroded multiple layers)

Question 15

law of superposition

Answer 15

the oldest rock on the bottom, the newest on top

Question 16

the law of inclusions

Answer 16

if a rock is found in the middle of a layer, the rock has to be older than the layer itself
layers form around older stuff

Question 17

law of cross cutting

Answer 17

if there is a fault or a dike, everything it cuts through is older than it

Question 18

fault

Answer 18

layers move diagonally. Everything that has been affected by the fault existed before the fault. Then after, layers formed horizontally
Look at pic on p 4

Question 19

dike

Answer 19

once layers have been laid
dike is a big hot igneous intrusion that shot from under the layers to the top
kind of a line cutting through layers

Question 20

law of unconformities

Answer 20

surfaces called unconformities (markers of missing time) represent gaps in the geologic record that formed wherever layers were not deposited for a time or else layers removed by erosion

Question 21

disconformity

Answer 21

unconformity between parallel layers

gap in time, something is missing

Question 22

anglular unconformity

Answer 22

between two sets of strata that are not parallel
all rules apply, layers are just tilted
the boundary between the tilted nd the horizontal layers is the angular unconformity

Question 23

nonconformity

Answer 23

between younger sedimentary rocks and subjacent metamorphic or igneous rocks
two different types of rock next to each other, the metamorphic or igneous protruded up over the layers