Why is it important that we have a rigid lithosphere overlying a weak asthenosphere?
If we did not have the rigid lithosphere an weak asthenosphere,the earth would not have plate tectonics and would be covered entirely by water.
Why is the molten metallic outer core and the magnetic field important to life on earth?
If we did not have the molten core and the magnetic field, we would be bombarded by cosmic rays that would strip away our atmosphere.
The Goldilocks scearino suggests that
We are very fortunate to be in the right place in the universe and to have had the right conditions to develop ans sustain life
The earth formed approximately how many years ago?
The heaviest element produced by nuclear fusion in a young star is
Planetesimals, asteriod-size objects, form during the early history of the solar nebula due to
Collisions of particles of ice, metal, and rocky material rotating about the protosun
What means the “the sun in the making”
As they formed, due to their high temperatures and comparatively weak gravitational fields, which planet were unable to retain appreciable amounts of hydrogen, helium, and ammonia?
Mercury and earth
Early earth was hot because
A combination of collisions and radioactive decay produced heat
Earths core, mantle, and crust formed during the
Which one of the following represents the greatest expanse of geological time?
The major source of free oxygen in the atmosphere is from
The process in which plants use light energy to synthesize food sugars from carbon dioxide is called
Earths primitive atmosphere evolved from gases
Expelled from within the earth
The waste gas released by plants as they synthesize food sugars from carbon dioxide and water is
The great oxygen event marks the time, appx 2.5 billion years ago, when _________.
There was significant oxygen in the atmsophere
The large size of insects and amphibians during the Pennsylvanian period has been suggested to be due to _______.
An excess of oxygen
The modern oceans are a major repository are the greenhouse gas ________, which some organisms utilize to make their shells
Banded iron formations are interbedded iron oxides and chert that formed on the sea floor between 3.5 and 2 billion years ago because
Iron was using the oxygen produced by bacteria and chert wasna common ocean deposit
One important reason we do not know much about the geologic-history of the Precambrian is that
Rocks did not exist during much of that time
Zircons found in continental rocks give evidence that continental crust was forming as long ago as
4.4 billion years ago
Continental crust is formed by
Melting and differentiation of oceanic crust at subduction zones
Antarctica became glaciated because
It moved to a position over the south pole
Sea level rise can be caused by
Fast seafloor spreading
Most __________ rocks are deviod of fossils, which hinders correlation of rocks
The Appalachian Mountains formed as a result of
The initial formations of pangea
The supercontinent of Pangea began to break up during the ___________ era
The beginning of the Phanerozoic is marked by the ________
Development of hard body parts, such as shells and bones
During the early Paleozoic era, South America, Africa, Australlia, India, and perhaps China comprised the vast southern continent of _______
By the close of the Paleozoic, all the continents had fused into the single super continent of _______
At the start of the Triassic, most of the continent were above sea level, and sediments from that time are often red because _______
They include iron oxides
The North American Cordillera formed as a result of ________
The subduction of the Pacific basin beneath North America
The most common Precambrian fossils are ______, layered mounds of calcium carbonate
Which tyoe of bacteria thrive in enviornments that lack free oxygen?
A major obstacle the first land planets had to overcome was ________
Their lack of mobility because they needed water access
An important evolutionary step for reptiles was _____
Lungs that could hold air reptiles
The first fully land-based animals were ____
The largest mass extinction in the Phanerozoic occurred in the ____
What group of animals were the first to leave the ocean to become the first amphibians?
Which era is sometimes called the “age of dinosaurs”?
Birds evolved from ____
One group of reptiles, exemplified by the fossil Archaeopteryx, led to the evolution of ____
Mammals became the dominant land animals during the ______ era.
The dominant life forms during the Cenozoic Era were _____
Mammals and angiosperms