Card Set Information
How do we use the name Precambrian
Informal - Time before Cambrian
Which range of Earth's history is represented by the Precambrian, in BY (billions of years)?
Which two rock types represents most of the Precambrian outcrop surfaces?
Igneous and metamorphic
What type of fossil is most representative of the Precambrian?
Where is found the largest North American Precambrian exposure?
Where can we find exposures of Precambrian rocks in Texas?
Llano, Carrizo Mt, Franklin Mt
How do we use the term "basement rocks"?
describes Precambrian rocks
Define a (Precambrian) shield
Define a platform
buried/covered surface of the shield
Define a craton
The nucleus of a continent made up of a shield and platform
What is the Canadian Shield?
What are the only representative "rocks" for the very beginning of the Haedean Eon?
What is Earth's oldest "particle" known and its age in BY?
What time period (BY) is represented by the Archean Eon?
4.0 BY - 2.5 BY
Which country do we find Earth's oldest crustal rocks?
Describe the effect of the moon on Earth's surface and oceans during the Early Archean Eon?
Crust rise & fall of 200ft and oceans deepen with 1k foot tides
When did a large number of meteorites stop pelting the Earth?
What type of tectonic feature can create continental crust?
oceanic subducted oceanic
Describe the rocks surrounding a typical Precambrian geologic province
granite / sediment
What is graywacke sandstone and what type of environment would it represent?
Abundant clay and volcanic rock fragments form in deep waters
What is a "greenstone"?
former volcanic and sediment rock rich in clorite
What do "greenstone" belts represent?
zones of rocks rich in clorite
Where do we find United States' oldest crustal rocks and what is the formation?
Minnesota River Valley
At what period of time was Earth's first ice age (BY)?
What is a tillitie? Sometimes it is also called a ___________?
Sedimentary deposits that include rocks and boulders from icebergs
How do we subdivide the Proterozoic Eon (using modifiers)?
What are banded iron formations?
alternating layers of iron oxides and chert deposited in the sea (chert = type of quartz)
Why do we no longer find BIF after 2.0 BY?
there was so much free oxygen that very minor dissolved iron would reach the ocean and there would be no more thick deposits
What tectonic event occurred near Missouri during the Middle Proterozoic Eon?
Mid-Continental Rift (North America trying to split apart but failed)
What mineral resources do the Keweenawan basalts contain?
large amounts of copper and silver metals
Which supercontinent was created with the Grenville Province?
How long was a typical day during the middle Proterozoic?
What famous Texas feature was created with the Grenville Province?
What is the snowball Earth theory?
Time when the entire Earth was covered in ice
Which super continent was created during the Late Proterozoic Eon?
All living matter is composed of at least four elements; what are the elements?
What is S.E.T.I.?
Search for Extra-Terrestrial Intelligence
What would be a primordial soup?
organic compounds, formed by a variety of processes, from molecules that accumulate in the shallow oceans
What is a microsphere?
Simple organic molecules that show great organizational complexity
How often has man been able to create life from chemicals?
What was Miller able to create?
all 20 amino acids
What is meant by chemical fossils?
fossil life detected by using non-radioactive isotopes of C12/C13 from "carbon films"
What is the difference between an autotroph and a heterotroph?
: organism that produces food inorganically
: organism that must consume organic molecules for survival (must eat other forms of alive or dead organisms)
What is cyanobacteria?
In what type of rock are most very early Precambrian fossils found (hint: chert)?
What is the approximate age (BY) of some of the oldest body fossils found?
What are stromatolites?
What are eukaryotes?
Why are arcitarchs?
Based on the fossil record, what represents the oldest know multicellular organism?
What are metazoans?
What type of fossil evidence do we have for very old metazoans?
What are Ediacaran fossils? (hard/soft; predator/prey; jaws/absorbing, etc)
Describe the climatic environment where Ediacaran organisms lived