Geology Exam 2
Prokaryotes (5)
simplest organism, single cell, single circular chromosome, do not have a nucleus, reproduce asexually
what are some characteristics of terrestrial planets (4)
small, dense, rocky, closer to the sun
when did the tippecanoe sea happen?
silurian
Prokaryote kingdoms
Bacteria, Archaebacteria
6 Kingdoms of life
Bacteria, Archaebacteria, Protists, Fungi, Plants, Animals
What would the temperature of Earth's surface be if there was no atmosphere?
-18 degrees celsius
What is Earth's average surface temperature today?
15 degrees celsius
when were detrital pyrites gone?
2.2 billion years ago
when did the Proterozoic era start?
2.5 billion years ago
What percentage of exposed rock is Precambrian?
20%
When did the Paleozoic era end?
252 million years ago
Age of oldest earth rock?
3.96 billion years
Age of the oldest material (some zircons) dated on Earth?
4.4 billion years old
When did the Paleozoic start?
541 million years ago
when did the Proterozoic era end?
541 million years ago
What percentage of continental material had already reached Earth's surface by the end of the Archean?
75% or more
What percentage of Earth time is represented by the Precambrian?
88%
distinctive unit of sedimentary rock of Precambrian age
Transitional banded iron formations (BIFS)
when were detrital pyrites abundant
Archean and early Proterozoic
when was there no oxygen?
Archean time period and before
growth of O2 in atmosphere - "free oxygen"
Atmospheric evolution
Oldest fossils found so far?
Both 3.48 b.y. cells on pillow lavas in South Africa and then 3.45 b.y. stromatolites in Australia
When and how did the core form?
Earth was molten, heavier elements such as iron and nickel moved rapidly toward Earth's interior to form the core
early in Earth history there was a lot less solar radiation (sun was not very strong), but the planet still had water
Faint Young Sun Paradox
how old are stromatolites?
Some stromatolites are among the most ancient fossils known, dating to about 3.5 billion years ago
hypothesis that the moon would initially have been relatively close to the Earth and gradually shifted away at a rate of about 4 centimeters per year
Giant Impactor Hypothesis
what are the two periods of the precambrian eon?
Hadean, Archean
examples of gas-giant planets (4)
Jupiter, Saturn, Uranus, Neptune
examples of terrestrial planets (4)
Mercury, Venus, Earth, Mars
Eukaryote kingdoms
Protists, Fungi, Plants, Animals
Grenville orogeny around 1 b.y. (Adirondack rx) North America was pretty much in center - South America to east and Antarctica to west!
Rodinia Supercontinent
the Earth's surface became entirely or nearly entirely frozen at least once, some time earlier than 650 million years ago
The Snowball Earth Hypothesis
first "modern" collisional orogenic belt in the Proterozoic era
Wopmay orogeny
when was the secondary atmosphere formed? (3)
after Earth accreted, most of the Hadean and part of the Archean
what is another name for the Archean Period?
age of continentalization
What would happen to the atmosphere and surface temperature if the Earth were a bit closer to the Sun? (2)
all the water that we have would evaporate to water vapor, runaway greenhouse
when does continental rifting break up Rodinia
around 800 million years ago
what happened overtime to the temperature of the sun and how did it effect the temperature of the Earth?
as the sun has gotten warmer and warmer over time the amount of CO2 in the atmosphere has gone down, temperature had stayed the same
If the Sun was 25-30% less bright early in Earth's history, how can we explain the existence of liquid water (not all frozen) on Earth's surface?
atmosphere had a lot more CO₂ which allowed the Earth to maintain a normal temperature
what elements were formed during the big bang nucleosynthesis
atomic numbers 1-5, (H, He, Li, Be and B)
what elements were formed during the stellar nucleosynthesis
atomic numbers 6-26 (C to Fe)
what elements formed during the supernovae
atomic numbers greater than 26
what are the 3 different processes where elements come from?
big bang nucleosynthesis, stellar nucleosynthesis, supernovae
theory that the universe originated sometime between 10 billion and 20 billion years ago from the cataclysmic explosion of a small volume of matter at extremely high density and temperature.
big bang theory
tons of rocks hitting the earth
bombardment
differences between ¹⁶O and ¹⁸O (2)
both have the same number of protons (8) but ¹⁸O has two more neutrons, ¹⁶O is easily incorporated into ice
Eukaryotes (4)
both single and multi celled, membrane bound nucleus, much larger than prokaryotes, contain organelles
when did the sauk sea happen?
cambrian
order of 7 Paleozoic time periods from oldest to youngest
cambrian, ordovician, silurian, devonian, mississippian, pennsylvanian, permian
what is important about zircons? (3)
can make a case that these zircons formed within continental felsic rock, if the age of these zircons is correct by this time there has to have been some felsic material "continental," would have to have ocean covering the continent with sediment
limestone that lies on top of, or cap, a glacial deposit
cap limestones
observation about the Moon's composition
chemical similarities between Earth and the Moon
temperature of the earth with high oxygen ratios
cold
How do we know what was going on in the Hadean since there are no rocks that age on Earth? (2)
computer modeling, using data from places where we do have rocks dated that old like the moon
if the ratio between ¹⁶O and ¹⁸O goes down (2)
conditions were warmer, some ice has melted putting ¹⁶O back into the ocean
Heterotrophic single-celled prokaryotes had to
consume food (did not make its own food)
how does continent arc collisions create continents? (2)
continent colliding with something that isn't subductable (ex: a volcanic arc), converting oceanic sediment to continent
what happened during the taconic orogeny? (3)
continent-arc collision, hits east coast, produced the queenston clastic wedge
what happened during the alleghanian orogeny? (3)
continent-continent collision, major collision, mountains would have been like the himalayas
what happened during the archdean orogeny? (3)
continent-continent collision, produced the catskill clastic wedge, was a mountain belt
What are the three processes by which new material (mostly felsic) is added to the continents?
continent-continent collisions, continent arc collisions, magma from subduction turning into continents
precambrian rock that underlies the continent - large portion of a continent that has been relatively undisturbed since the Precambrian era and includes both shield and platform layers. Contrast with shield
craton
when did the kaskaskia sea happen?
mississippian
What is the evidences that there was very little to no free oxygen in the Archean atmosphere/oxygen had started to accumulate in the Proterozoic? (2)
detrital pyrite (iron sulfate), Paleosols (ancient soils or weathering profiles that indicate the oxidation state of the Earth) in the Archean time period
when did the archdean orogeny happen?
devonian
Where did the salts in the ocean come from?
dissolved sediment from weathering rocks like granite
3 factors that determine the surface temperature of a planet
distance from the sun, albedo (reflectivity), greenhouse gasses
Normally, when there is a balance between photosynthesis and respiration/decay, the ratio between the two isotopes ¹²C and ¹³C ...
doesn't change
rock that was carried by a glacier or iceberg, and deposited as the ice melted
dropstones
proposal that certain organelles, especially mitochondria and chloroplasts, originated as free-living bacteria that were taken inside another cell as organisms that live within the body or cells of another organism
endosymbiotic theory of cell evolution
how do stromatolites form?
formed in shallow water by microorganisms
zone of high grade Archean rock that has been differentially exhumed (dug out) relative to surrounding rock formations
gneiss terrane
what are the two classifications of Archean continents?
gneiss terrane, greenstone belts
component of the Earth's crust made up of a variety of coarse grained plutonic rock similar to granite which mineralogically are composed predominantly of feldspar or quartz
granitoid
What are the hallmarks of "life"? (5)
has to be able to store information and transmit it to offspring, has to have a cell membrane (separating it from its environment), has to exchange and harness energy and matter with the environment, complexity, ability to evolve or adapt
The planet Earth was much hotter during the Precambrian - where does Earth's heat come from? (2)
heat of formation of the planet (kinetic energy), radioactive decay (releases heat that keeps the earth hot)
what do we know about the solar system? (4)
held together by gravity, all planets in the rotational plane around the sun, all planets rotating the same direction around the sun, planets must have formed around the same time as the sun
if the ratio between ¹⁶O and ¹⁸O goes up (2)
ice volume increased, ¹⁶O is taken from seawater
how does continent-continent collisions create continents? (2)
in between the two continents it scrapes up sediments and other stuff from the ocean that did not get subducted, converting oceanic sediment to continent
what is a nebula?
interstellar cloud of dust, hydrogen gas, helium gas, and other ionized gasses
Most of the planet is composed of what 4 elements?
iron, oxygen, silicon, magnesium
equal number of protons, but different number of neutrons in the nucleus
isotopes
what happened when detrital pyrites disappeared?
it was oxidized to produce sulfates (created oxygen)
What would happen to the atmosphere and surface temperature if the Earth were a bit farther from the Sun? (2)
it would get colder, runaway glaciation
what are some characteristics of gas-giant planets (3)
large, low density, farther from the sun
when organic activity decreases what happens to the carbon isotopes?
less ¹²C in rocks
Paleosols in the Archean time period (older than 2.2 billion years old)
lost much of their iron, presumably because it was dissolved away
What happens to the ratio of carbon isotopes in a pulse of organic burial (without decay)? (3)
lots of ¹³C, hidden ¹²C, higher ratio
how does magma from subduction create continents?
melting a bit of the mantle that comes into the continents in a subduction zone
what are zircons?
silicate mineral
Once enough debris from the nebula had coalesced to form the planet, was Earth initially a molten object or a solid object?
molten
how do continents form? (3)
more and more felsic material (lighter), lighter than the mantle so it is harder to subduct, accumulates as continents
what is the runaway glaciation loop?
more ice formed, albedo goes up (reflects solar radiation away), causes more ice to form ...
when organic activity increases what happens to the carbon isotopes?
more ¹²C in rocks
What happens to the ratio of carbon isotopes in the ocean and atmosphere (13C/12C) when there is a pulse of photosynthetic activity? (2)
more ¹²C is soaked up into organic matter, ratio will be higher
where did the water for Oceans come from? (2)
mostly from comets that have hit the planet, partly from the Earth's interior through volcanic outgassing
two observations that support the Solar Nebula explanation
nine planets that lie in or very close to the plane of the ecliptic, all planets rotate counterclockwise around the sun in nearly circular orbits
What effect did the core have on Earth's magnetic field?
once the core formed it developed a magnetic field
section of the Earth's organic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks
ophiolite
when did the taconic orogeny happen?
ordovician
sediment deposited before, during, and after collision as mountains grow and weather
orogenic clastic wedges
What are the 2 most abundant elements?
oxygen, iron
when did the alleghanian orogeny happen?
pennsylvanian
when did the absaroka sea happen?
permian
geological process by which the earth came to have its present interior structure
planetary differentiation
how was the Proterozoic era more modern? (3)
plate tectonics clearly operating, modern-type subduction zones, relatively mature continental shelf sediments
is the runaway glaciation loop positive or negative feedback?
positive
is the runaway greenhouse loop positive or negative feedback?
positive
precambrian rocks that are exposed - ancient, stable, interior layer of continents composed of primarily Precambrian igneous or metamorphic rocks
precambrian shield
did plate tectonics occur during the Archean Period?
probably
how does a nebula form?
produced when you explode a star
How did the magnetic field help the Earth retain atmospheric gasses? (2)
protects both the gasses and the atmosphere, began accumulating gasses in the atmosphere
was the formation of the Earth's core quick or slow?
quick
What is the evidence that Earth is 4.6 billion years old?
radiometric age dating
Why is it so hard to figure out what happened during the Precambrian? (3)
record is not there, few fossils, fewer index fossils
What are the alternating layers in BIFS made of?
repeated, thin layers of iron and a red form of chert called jasper
Paleosols in the proterozoic time period (younger than 2.2 billion years old)
retained much of their iron because it was precipitated in the presence of oxygen
Oldest evidence for biological activity on Earth?
rocks containing carbon
plane of ecliptic definition
same plane as the Earth's orbit around the sun
Flooding of NA - epicontinental seas transgressions/regressions - 4 events in NA
sauk sea, tippecanoe sea, kaskaskia sea, absaroka sea
¹⁶O and ¹⁸O are both present in
seawater
When did the Moon form?
shortly after differentiation occured
What happened on Venus? (2)
so close to the sun, water could not be a liquid (evaporate immediately, gas would be broken apart and lost into space)
hypothesis of the formation of the solar system according to which a rotating nebula cooled and contracted, throwing off rings of matter that concentrated into the planets and their moons, while the great mass of the condensing nebula became the sun
solar nebula
large mineral structures
stromatolites
major fault zone through an orogen or mountain range
suture
Orogenic events (especially North America and 3 events forming Appalachians)
taconic orogeny, archdean orogeny, alleghanian orogeny
what are the two types of planets?
terrestrial, gas-giant (jovian)
when did oxygen start to develop?
the Proterozoic time period
how is the Faint Young Sun Paradox possible?
the atmosphere had a lot more CO2, stayed within a good temperature
what was the Snowball Earth Hypothesis trying to explain? (2)
the ice age, if/how glaciation happened in the tropics
the Giant Impactor Hypothesis accounts for (2)
the inclined orbit of the moon, the angular momentum
all rocks exposed on the east coast except for the adirondacks are either metamorphic or igneous rocks part of
the orogenic events
How did the Moon form? (2)
the planet got slammed by a rather large object, took a chunk of the earth to form the moon (impact remelted Earth's crust and most of the mantle)
How can carbon isotopes be used to tell us when organic activity on Earth began? (2)
there are rocks that are 3.8 billion years old with carbon in them, isotope record suggests that the carbon was formed by biological activity
how does the secondary atmosphere develop?
volcanic gasses (outgassing)
the release of gasses into the atmosphere during volcanic eruptions
volcanic outgassing
temperature of the earth with low oxygen ratios
warm
what is the runaway greenhouse loop?
water vapor is a greenhouse gas so the temperature of the earth would go up, more water would evaporate, cause more water vapor to increase the temperature ....
what was in the secondary atmosphere originally (5)
water vapor, Co2, nitrogen, sulfur gases, carbon monoxide
What kinds of things can happen to alter or destroy the rocks formed during the Precambrian? (3)
weathering, metamorphism, buried
Is differentiation still occurring?
yes
During the process of photosynthesis, which isotope is preferentially used? (incorporated into organic matter)
¹²C (lighter form of carbon)
difference between ¹²C and ¹³C (2)
¹³C is more rare and heavier
When water evaporates from the ocean (to form glaciers on land for example), which isotope is preferentially evaporated?
¹⁶O (the lighter one)