Upgrade to remove ads
Only $2.99/month

Ch. 22 Study Guide

Terms in this set (63)

The Precambrian is the oldest part of the geologic time scale
True
The Precambrian lasted for about 4 billion years.
False
The first organisms to live on earth were dinosaurs
False
Radiometric dating of zircon grains in metamorphosed sedimentary rocks in Australia indicate that Earth is about 3.1 billion years old.
False
The oldest moon rocks collected are about 3.6 billion years old.
False
Scientists think that Earth and meteorites are about the same age because they hypothesize that the solar system formed all at once.
True
How do radioactive isotopes add to earth's heat?
Radioactive isotoopes decay and they released heat, more heat was generated and earth was hotter than it is today.
How has the amount of earths radioactive isotopes changed over time, and why has it changed?
Radioactive isotopes have died out and it caused the earth to be cooler than it used to be.
What is an asteroid?
Asteroids are carbon or mineral-rich object between 1m and 950 km in diameter
What is a meteorite?
Meteorites and Earth are the same age and have been falling since the beginning. Meteorites are asteroids that have fallen to earth
How did continuous bombardment by meteorites and asteroids affect the temperature and size of earth?
It generated thermal energy.
How did gravitational contraction affect Earth?
It combined with radioactivity and bombardment by other objects and made Earths beginning very hot.
When Earth Formed, the dense element _____ was concentrated in Earth's core.
Iron
The deepest and most stable part of a continent is called a ____.
Craton
The common crustal rock ______ is mainly composed of feldspar, quartz, and mica, which are minerals with low densities.
Granite.
Early Earth's crustal fragments, or micro-continents, formed on Earth's surface by
Volcanic Activity
Denser minerals concentrated below Earth's surface and formed the rocks that make up earth's _____.
Mantle
The process by which a planet becomes internally zoned is called
Differentiation
Earths _____ probably formed as a result of the cooling of the uppermost mantle
Crust
Sediment-covered slabs of earths earliest crust were recycled into the mantle at ____ zones.
Subduction
Less-Dense material such as crust has a tendency to _____ on more-dense material such as mantle.
Float
A difference in density causes the _____ to be lower in elevation than the less-dense granitic continental crust.
Oceanic-Crust
General name for a core of Archean and Proterozoic rock
Craton
North American core of Proterozoic Rock
Canadian Sheild
Can be seen over a large part of Greenland
Precambrian sheild
Buried and most stable parts of a shield
Craton
What is Laurentia?
One of the Earths largest protozoic landmasses.
What is a microcontinent?
They are not large enought to be continents.
What is the seam called that forms when two microcontinents join together?
Orogeny
What happened when volcanic islands collided with Laurentia between 1.8 and 1.6 billion years ago?
The formation of Earths first super continent
Describe the Grenville Orogeny
Belts of deformed rocks.
What was the name of the first super continent, and when did it form?
South America, in mid-Proterozoic.
What two gases probably dominated Precambrian Earth's atmosphere?
Hydrogen and helium
Why is Earth's atmosphere no longer rich in Hydrogen and Helium today?
The gravity isn't strong enough to hold it.
What occurs during the process of outgassing and what role did this play in the formation of the atmosphere?
Volcanoes erupt the gases such as water vapor, carbon dioxide, and trace amounts of nitrogen and other gases. This plays the in the process of the formation of the atmosphere by making the gas go into the atmosphere. As the volcano erupts the gases are released and absorbed into the atmosphere.
What is the likely source of oxygen in the early atmosphere?
Cyanobacteria
Did oxygen exist in the atmosphere during the Proterozoic? Explain your answer.
Yes, but it was in large amounts amounts because there wasn't anything to take away or contaminate the oxygen.
What is a banded iron formation?
Locally concentrated iron oxides.
Seawater probably originated largely from the same process of______ formed the atmosphere
Water vapor
A major component of the gas that was vented from early Earth was______
outgassing.
As the early atmosphere and surface of Earth cooled, the water vapor in the atmosphere condensed to form
oceans
During the ______ rain slowly filled the low-lying areas on Earth.
Archean
The low-lying areas were underlain by basalt, and as these basalt-floored basins filled, they formed the ____
Liquid water
Rainwater reacted with the _______ exposed at earths surface and dissolved them, making the oceans of the Precambrian salty.
Minerals
In Miller and Urey's experiment, what gases were contained in the atmospheric chamber, and what were these gases meant to simulate?
Hydrogen, methane and ammonia
The Earths atmosphere.
What was simulated by the sparks from the tungsten electrodes?
Lightning
What was contained in the "primordial soup" created by this experiment?
Organic molecules, amino acids
Why do some scientists theorize that life did not arise from a "primordial soup"?
Amino acids could not form in high quantities in early earth.
What did miller and Urey demonstrate about the basic building blocks of life?
Amino Acids are needed.
This has been found in waters of hydrothermal vents
Amino Acids
These are needed by RNA and DNA for reproduction in modern organisms
Enzymes
Sites were life may have originated
Hydrothermal vents
Essential characteristic of life
Ability to reproduce
May have beem first self-replicating molecules on earth
RNA
An organism composed of a single cell, which does not contain a nucleus and is the simplest kind of cell is,
An eukaryote
An organism composed of sells that contain a nuclei is a
Prokaryotes
Euckaryotes differ from prokaryotes in that most eukaryotes are
Smaller
The oldest known fossil eukaryotes are
Related to cyanobacteria
Because of their bizarre body forms, scientist question whether the Ediacaran biota were
Lacking a mouth, anus, or gut
Near the end of the proterozoic a major extinction may have been linked to
The formation of the ozone layer
The ediacaran biota are generally believed to be
Animals composed of eukaryotic cells.
Ediacaran biota proably were widely distributed in the oceans of the
Early cambrian
The absence of tracks and trails leads scientists to speculate that the Ediacaran fuana were
Plants
YOU MIGHT ALSO LIKE...