Very Easy
Easy
Medium
Difficult
Extremely Difficult
100
71 percent
What is the percentage of ocean in the Earth?
100
oxidized iron
What was deposited on lake and sea bottoms?
100
Declination of iron rich deposits
What caused oxygen levels to increase?
100
Iron rich sedimentary rocks
What rocks show the abundance of Oxygen?
100
LOOK AT MAP. Metamorphosed igneous and sedimentary rocks.
What are the continental shields composed of?
200
29 percent
What is the percentage of land on Earth?
200
1.2 billion to 2.5 billion years ago
What is the time for Middle Precambrian era?
200
Iron, nickel, gold, silver, copper, chromium, Uranium, diamonds.
What has revealed precambrian rocks?
200
Plant photosynthesis
Where does free oxygen come from?
200
Continental shields (LOOK AT MAP)
What are remnants of Precambrian rocks?
300
Paleozoic, Mesozoic, and Cenozoic rock surfaces.
What are the surfaces orbiting space scientists gaze upon?
300
Middle Precambrian
What time period contains most of earth's iron ore?
300
Older on bottom, younger on top
What is the law of superpostition?
300
Precambrian iron ore deposits
What is linked to life in the sea?
300
absence of land plants
What is the reason for lack of fossil fuels?
400
Precambrian surfaces
What is the least found surface by orbiting space scientists?
400
10 of Texas put together
What is the size of the Canadian shield equivalent of?
400
7.2 million square kilometers
How many square kilometers does the Canadian shield encompass?
400
mining the ores
Where does our knowledge of precambrian rocks come from?
400
Very different (LOOK AT MAP!!)
How does todays continent look in relation to the Precambrian time?
500
resembles warrior shield
What do shields resemble?
500
Iron
What was oxidized and deposited?
500
deformed metamorphic rocks
What form do Precambrian rocks take as they dominate surfaces on each continent?
500
fossil fuels
What is absent in the precambrian?
500
Fe2O3
What is the mineral hematite?
M
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