Lecture 3

Question 1

In terms of time what are the important events in the earths history?

Answer 1

at 12 there’s the moon, at 1 first life, at 4 photosynthesis, at 6 oxygenated atmosphere, at 8 am multicellular life, at 10 animals in the sea, at 11 animals on land, at 11:#0 dinos, at 11:45 dinos extinct

Question 2

The geologic time scale is what?

Answer 2

a calender of events in earth’s history

Question 3

Dinosaurs lived during which era?

Answer 3

The mezosoic era

Question 4

What periods is the mezosoic era composed of?

Answer 4

The cretaceous (145 to 65.5 Ma)
The jurassic (200 Ma to 145 Ma)
The triassic (252 to 200 Ma)

Question 5

When were the first dinosaurs? The last?

Answer 5

228 Ma in triassic
Last were in cretaceous at 65.5 Ma

Question 6

How is the geologic time scale built?

Answer 6

is built by studying rocks and the
fossils within them.

Question 7

What are the three main rock types?

Answer 7

Igneous (solidify from melted rocks)
Sedimentary (broken or dissolved bits of other rocks stuck together)
Metamorphic (Heated and squeezed rocks)

Question 8

What are the two common types of sedimentary rock?

Answer 8

Clastic and chemical
Clastic rocks are rocks that are formed from Sediments deposited on land/beaches/ in
rivers, buried, then glued together to make a rock
chemical rocks are Sediments crystallize out of water, Form in lakes/seas due, sometimes due to
evaporation

Question 9

What are the types of clastic sedimentary rocks?

Answer 9

sandstone,
siltstone, shale

Question 10

What are the types of chemical sedimentary rocks?

Answer 10

limestone, salt

Question 11

How do weathering and erosion produce sediment?

Answer 11

the exposed rocks are subjected to wind, rate, heat, and cold, this breaks them down (weathering) then they travel and get deposited into low lying areas (erosion)

Question 12

sediments cand be deposited where?

Answer 12

on the edges of glaciers, on beaches, in rivers, or on the sea floor

Question 13

What happens to grain size as the sediment is moved away from the source?

Answer 13

gets smaller because it gets weathered more

Question 14

How do sediments get deposited in basins?

Answer 14

As the land flattens our rivers slow down and deposit sediment, the slower the war gets the more finer sediment it deposits, this is how basins fill up with sediment over time as rivers run through them

Question 15

What is a foreland basin?

Answer 15

The weight of the mountain belt pushes down on the crusts surface causing a basin to form

Question 16

What is a rift basin?

Answer 16

A downward slip on a fault produces narrow troughs

Question 17

What is a intracontinental basin?

Answer 17

this basin forms in the middle of a continent over an old rift

Question 18

What is a passive margin basin?

Answer 18

the thinned crust at the edge of an ocean gets pushed down (subsidence) forming a basin

Question 19

What is the western canadian sedimentary basin, how did it form?

Answer 19

Is a basin the alberta and BC, formed due to the heavy load of mountains in BC causing the plate to sink

Question 20

What are examples of sedimentary structures contained in sediment layers?

Answer 20

Asymmetrical ripples in river and deserts
symmetrical ripples in areas of oscillating wave action
imbricated pebbles in rivers
mudcracks from when water dries up and clay minerals contract

Question 21

Lithification is caused by what two things?

Answer 21

compaction and cementation

Question 22

How can we infer the environment dinosaurs lived in?

Answer 22

by studying the clastic sedimentary rocks around it

Question 23

What are the two types of dating you can use to date rocks?

Answer 23

relative dating (You put events in order relative to eachother) via Lithostratigraphy (rocks)
Biostratigraphy (fossils)

absolute dating (know the exact date) do this via radiometric dating

Question 24

How is relative dating done?

Answer 24

Putting rocks/events in order from oldest to youngest
Determined using the seven stratigraphic principles of
relative dating

Question 25

Define strata?

Answer 25

layers of sedimentary rock (singular: stratum)

Question 26

Define stratigraphy?

Answer 26

the study of rock layers

Question 27

What is principle of superposition?

Answer 27

Sediments get stacked over time. Because of gravity, the oldest sediments are usually on the bottom.

Question 28

What is the principle of original horizontality?

Answer 28

Sediments that have been deposited in horizontal layers can be deformed into folds or broken by faults.

Question 29

What is the principle of lateral continuity?

Answer 29

Because sediments are deposited in horizontal layers, you can trace undeformed layers from one rock outcrop to another, even when some of the layer has been eroded (washed away by wind/water)

Question 30

What is the principle of cross cutting relationships?

Answer 30

A geologic feature that cuts across another is younger than the feature it cuts across.

Question 31

What is the principle of inclusions?

Answer 31

A rock inclusion is older than its host. (The inclusion had to exist first in order to be incorporated into another unit.)

Question 32

What is the principle of uncomformities?

Answer 32

Rocks above an unconformity (an erosional surface) are younger than the rocks below. Unconformities mean there is time missing from the rock record

Question 33

What is the principle of faunal succession?

Answer 33

extinct animals will only appear in rocks that formed when it was alive and fossils of different animals will succeed each other vertically in a predictable, specific order.

Question 34

What is biostratigraphy?

Answer 34

uses fossils to tell time, for ex index fossiles are ones that are widespread and have existed for a short range of geologic time and are used to correlate rocks of the same age

Question 35

Atoms are what?

Answer 35

the smallest components of nature with the properties of a given substance

Question 36

What isotopes?

Answer 36

atoms with same protons but diff neutrons

Question 37

How do you do absolute dating?

Answer 37

radioactive isotopes break down into daughter isotopes over time, you can measure their half-lifes (the amnt of time it takes for half the sample to break down) to see how long the atom has been around by measuting the ratio of parent to daughter isotopes for ex 25 to 75 means its gone through three half lives

Question 38

Can all isotopes work for radioactive dating?

Answer 38

No, The isotope must be present in the sample to begin with and There must be measurable quantities of both the parent and the daughter in the rock, so you must choose an isotope that doesn’t decay to fast or too slow relative to the expected age of the rock (if it decays quickly, there will be not be enough parent left, so it is no longer keeping track of time)

Question 39

Is carbon an appropriate isotope for dating dinosaurs?

Answer 39

no because it's half life is 50000 years so it can't date rocks that are millions of years old, the parent will be all gone.

Question 40

How do you determine the age of a rock (igneous versus seidmentary)?

Answer 40

the minerals in volcanic rocks have isotopes so you can figure out when those are formed, sedimentary rocks also contain isotopes but they won't tell date of the rocks just the age of the mineral that has the isotope

Question 41

What is the dorothy bentonite?

Answer 41

is a thick layer of volcanic ash and is estimated to be 73 Ma, is SE of drumheller