Geology - Test 3

Front 1

Explain the difference between relative dating and absolute dating in geology.

Back 1

Relative dating means placing rocks in their proper sequence of formation, what formed 1st, 2nd, etc.

absolute is like you using radioactivity and such

Front 2

Who discovered the immensity of time? When did he do this?

Back 2

o Late 1700s, James Hutton of Scotland disagreed
 Observed slow pace of natural processes
 Enunciated principle of uniformitarianism
 “The present is the key to the past.”
• The processes and physical laws operating today also operated in the past
• With enough time, earth history could be explained without catatrophism
 Concluded earth was incomprehensibly old
 Hutton’s epiphany at Siccar Point, Scotland
• Hutton had previously observed slow pace of geologic processes
 At Siccar Point, saw that once horizontal sedimentary layers
• Were raised above sea level
• Were turned one end
• Were eroded down
• Sank below sea again
• New horizontal layers were deposited over them
o Then the new layers themselves had been raised above sea level, tilted and eroded down
• Realized huge amounts of time were required
o Discovered deep time (geologic time)
o Didn’t estimate earth’s age

Front 3

Explain the "principle of cross-cutting relationships", and give three different geologic examples.

Back 3

when a fault cuts through other rocks, or when magma intrudes and crystallizes, we can assume that the fault or intrusion is younger than that rocks affected

Front 4

Sketch a roadcut revealing an angular unconformity and point to and list the sequence of four geologic events that can always be inferred by an angular unconformity.

Back 4

-deposited
-folded/tilted
-erosion

Front 5

Explain the "principle of fossil succession".

Back 5

Fossil organisms succeed one another in a definite and determinable order, and therefore any time period can be recognized by its fossil content

Front 6

What fundamental principle of geology says that, unless a stack of sedimentary rocks has been flipped upside down, the oldest layer is the one on the bottom?

Back 6

Law of Superposition - in an underformed sequence of seimentary rocks, each bed is older than the one abovie it and younger than the one below it

Front 7

Which rule lets you conclude that an igneous rock that cuts through a sedimentary rock must be younger than that sedimentary rock?

Back 7

when a fault cuts through other rocks, or when magma intrudes and crystallizes, we can assume that the fault or intrusion is younger than the rocks affected

Front 8

What does the Principle of Original Horizontality say?

Back 8

the layers of sediment are generally deposited in a horizontal position

Front 9

What has to happen to produce an unconformity?

Back 9

an unconformity represents a long period during which deposition ceased, erosion removed previously formed rocks, and then deposition resumed.

-In each case, uplift and erosion are followed by subsidence and renewed sediment -

Front 10

Define half-life.

Back 10

the time required for half of the nuclei in a sample to decay

Front 11

One day you put some radioactive isotopes of element X in a box and seal it up. When you come back two years later, the box contains 25% of element X and 75% of daughter isotope Y. What is the half-life of X?

Back 11

1 year

Front 12

Explain how radiometric dating works, using the terms "parent", "daughter", and "half-life".

Back 12

parent = an unstable (radioactive) isotope of an element

daughter = the isotopes resulting from the decay of the parent

half-life =

Front 13

Consider a rock containing a radioactive isotope that has a half-life of 60 million years. If that rock is found to contain 1 part parent isotope to 7 parts daughter product from that isotope, how old is that rock?

Back 13

1:0 - 100/0
1:1 - 50/50
1:3 - 25/75
1:7 - 12.5/87.5

so three half lives, 3x60=180million years

Front 14

The half-life of 235U is about 700 million years. 235U decays to 207Pb. Zircon crystals from granite have been analyzed by the 235U/207Pb method. Of these two isotopes, the zircons have 235U = 25%, 207Pb = 75%. How old is the granite?

Back 14

2 half lives have passed...
700x2=1400million years

Front 15

The half-life of 235U is about 700 million years. 235U decays to 207Pb. Zircon crystals from granite have been analyzed by the 235U/207Pb method. Of these two isotopes, the zircons have 235U = 12.5%, 207Pb = 87.5%. How old is the granite?

Back 15

3 half lives have passed
3x700=2100million years

Front 16

The half-life of 235U is about 700 million years. 235U decays to 207Pb. Zircon crystals from granite have been analyzed by the 235U/207Pb method. Of these two isotopes, the zircons have 235U = 50%, 207Pb = 50%. How old is the granite?

Back 16

700 million years x 1 (half life) = 700 million

Front 17

Give at least one good reason why most sedimentary rocks cannot be dated by radiometric techniques.

Back 17

different particles, different dates, etc.etc.

Front 18

During which Era did the dinosaurs live?

Back 18

Mesozoic Era (think triassic)

Front 19

How long ago was the end of the Cretaceous Period? What major event affected Earth's climate at the end of that period?

Back 19

65 million years, large meteriote - chicxulub crater - yucatan

KT borter

Cretaceous/Tertiary

Front 20

How long did the Precambrian eon last?

Back 20

4 billion years or less

Front 21

The earliest-known fossils appear to be what kind of organism?

Back 21

bacteria (cyanobacteria) no nucleus

Front 22

About how old are the earliest known fossils?

Back 22

3.5 billion years old

Front 23

Why are bacteria considered to be the simplest life forms?

Back 23

„X Single cells
„X Cells have no nucleus ¡V distinguishing factor
„X Only bacteria have prokaryotic cell (everything else is eukaryotic)
„X Reproduction is asexually (by binary fission), so offspring is ¡§carbon copy¡¨ of parent ¡V one organism divides itself in two

Front 24

Name some organisms besides bacteria that have prokaryotic cells.

Back 24

ONLY BACTERIA HAVE PROKARYOTIC CELLS!

Front 25

After bacteria appeared on Earth, they were the sole known forms of life for the next ________ years.

Back 25

2 billion years

Front 26

What is the most important distinction between eukaryotic cells and prokaryotic cells?

Back 26

EUkaryotics cells have a nucleus

Front 27

Name some organisms with prokaryotic cells.

Back 27

bacteria!

Front 28

What is a Moneran?

Back 28

organisms that typically reproduce by asexual budding or fission and whose nutritional mode is absorption or photosynthesis or chemosynthesis

Front 29

Name at least 5 multi-cellular eukaryotes and at least 1 uni-cellular eukaryote.

Back 29

dog, cat, hamster, gerbil, person,


AMOEBA!

Front 30

Why did the advent of sexual reproduction speed up evolution?

Back 30

„X Allows rapid shuffling of gene pool
„X New gene combinations arise continually ¡V creating diversity
„X Offspring not necessarily ¡§carbon copy¡¨ of parent ¡Kthink natural selection
„X Evolutionary ¡§fast track¡¨


it happened about 1 billion years ago

Front 31

About how old are the oldest known multicellular plants and animals?

Back 31

900million-1billion years ago IN OCEAN

Front 32

whats this whole Ediacara thing

Back 32

soft shelled stuff, like jelly fish

Front 33

In very old rocks, the fossil record is fairly poor. But beginning in the Cambrian Period, the fossil record improved dramatically. What happened in the Cambrian Period that led to an improved fossil record?

Back 33

the hard parts, teeth, shells, bones?

Front 34

The Phanerozoic Eon of geologic time is divided into three Eras. What forms the basis for recognizing three eras? (Another way to say this is: "What ends one Era and starts a new one?")

Back 34

extinctions?

Front 35

How did the Mesozoic Era end?

Back 35

65million years ago, bye bye dinosaurs

Front 36

How many mass extinction events have occurred during the Phanerozoic Eon?

Back 36

?

Front 37

During which Era of geologic time did the dinosaurs live?

Back 37

Mesozoic

Front 38

What is Earth's human population?

Back 38

?

Front 39

List the 3 types of loads carried by streams.

Back 39

bed load, suspended load, dissolved load

Front 40

What is meant by stream gradient and how is it calculated?

Back 40

slope of stream channel, vertical drop/hortizontal distance

Front 41

Explain what scroll bars reveal about a stream channel's movement.

Back 41

scroll bars are old point bars

Front 42

What is a hydrograph?

Back 42

record of water level over time

Front 43

Which segment of the U.S. economy uses the most groundwater?

Back 43

agriculture

Front 44

Compare the amount of groundwater on Earth with the amount of water in rivers and lakes.

Back 44

groundwater = .62%
rivers and lakes = .01%

Front 45

Define porosity.

Back 45

the percentage of the total volume of rock or sediment that consists of pore spaces

Front 46

Define permeability.

Back 46

it's ability to transmit fluid

Front 47

Describe a cone of depression and explain what causes it.

Back 47

think over drawn well, = draw down

Front 48

How high will water rise in a well drilled into an unconfined aquifer?

Back 48

the water table

Front 49

What is "drawdown"?

Back 49

think of the telephone pole

Front 50

Explain at least two potential negative consequences of drawdown.

Back 50

contamination and land subsidence

Front 51

Explain what speleothems are and give some examples

Back 51

stalactities, and stalagmites