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51 Cards in this Set

  • Front
  • Back
Explain the difference between relative dating and absolute dating in geology.
Relative dating means placing rocks in their proper sequence of formation, what formed 1st, 2nd, etc.

absolute is like you using radioactivity and such
Who discovered the immensity of time? When did he do this?
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
Explain the "principle of cross-cutting relationships", and give three different geologic examples.
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
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.
Explain the "principle of fossil succession".
Fossil organisms succeed one another in a definite and determinable order, and therefore any time period can be recognized by its fossil content
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?
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
Which rule lets you conclude that an igneous rock that cuts through a sedimentary rock must be younger than that sedimentary rock?
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
What does the Principle of Original Horizontality say?
the layers of sediment are generally deposited in a horizontal position
What has to happen to produce an unconformity?
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 -
Define half-life.
the time required for half of the nuclei in a sample to decay
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?
1 year
Explain how radiometric dating works, using the terms "parent", "daughter", and "half-life".
parent = an unstable (radioactive) isotope of an element

daughter = the isotopes resulting from the decay of the parent

half-life =
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?
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
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?
2 half lives have passed...
700x2=1400million years
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?
3 half lives have passed
3x700=2100million years
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?
700 million years x 1 (half life) = 700 million
Give at least one good reason why most sedimentary rocks cannot be dated by radiometric techniques.
different particles, different dates, etc.etc.
During which Era did the dinosaurs live?
Mesozoic Era (think triassic)
How long ago was the end of the Cretaceous Period? What major event affected Earth's climate at the end of that period?
65 million years, large meteriote - chicxulub crater - yucatan

KT borter

How long did the Precambrian eon last?
4 billion years or less
The earliest-known fossils appear to be what kind of organism?
bacteria (cyanobacteria) no nucleus
About how old are the earliest known fossils?
3.5 billion years old
Why are bacteria considered to be the simplest life forms?
„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
Name some organisms besides bacteria that have prokaryotic cells.
After bacteria appeared on Earth, they were the sole known forms of life for the next ________ years.
2 billion years
What is the most important distinction between eukaryotic cells and prokaryotic cells?
EUkaryotics cells have a nucleus
Name some organisms with prokaryotic cells.
What is a Moneran?
organisms that typically reproduce by asexual budding or fission and whose nutritional mode is absorption or photosynthesis or chemosynthesis
Name at least 5 multi-cellular eukaryotes and at least 1 uni-cellular eukaryote.
dog, cat, hamster, gerbil, person,

Why did the advent of sexual reproduction speed up evolution?
„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
About how old are the oldest known multicellular plants and animals?
900million-1billion years ago IN OCEAN
whats this whole Ediacara thing
soft shelled stuff, like jelly fish
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?
the hard parts, teeth, shells, bones?
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?")
How did the Mesozoic Era end?
65million years ago, bye bye dinosaurs
How many mass extinction events have occurred during the Phanerozoic Eon?
During which Era of geologic time did the dinosaurs live?
What is Earth's human population?
List the 3 types of loads carried by streams.
bed load, suspended load, dissolved load
What is meant by stream gradient and how is it calculated?
slope of stream channel, vertical drop/hortizontal distance
Explain what scroll bars reveal about a stream channel's movement.
scroll bars are old point bars
What is a hydrograph?
record of water level over time
Which segment of the U.S. economy uses the most groundwater?
Compare the amount of groundwater on Earth with the amount of water in rivers and lakes.
groundwater = .62%
rivers and lakes = .01%
Define porosity.
the percentage of the total volume of rock or sediment that consists of pore spaces
Define permeability.
it's ability to transmit fluid
Describe a cone of depression and explain what causes it.
think over drawn well, = draw down
How high will water rise in a well drilled into an unconfined aquifer?
the water table
What is "drawdown"?
think of the telephone pole
Explain at least two potential negative consequences of drawdown.
contamination and land subsidence
Explain what speleothems are and give some examples
stalactities, and stalagmites