precambrian plate tectonics

precambrian plate tectonics

By the end of the Archean, about 2.5 billion years ago, plate tectonics processes were completely recognizable. Small Proterozoic continents known as microcontinents collided to create supercontinents, which resulted in the uplift of massive mountain ranges. The history of the North American craton is an example of what generally happened to the cratons during the Precambrian. As the craton drifted, it collided with microcontinents and oceanic island arcs, which were added to the continents. Convergence was especially active between 1.5 and 1.0 billion years ago. These lands came together to create the continent of Laurentia. About 1.1 billion years ago, Laurentia became part of the supercontinent Rodinia (Figure 1.1). Rodinia probably contained all of the landmass at the time, which was about 75% of the continental landmass present today. Rodinia broke up about 750 million years ago. The geological evidence for this breakup includes large lava flows that are found where continental rifting took place. Seafloor spreading eventually started and created the oceans between the continents. The breakup of Rodinia may have triggered Snowball Earth around 700 million years ago.

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questions

in the snowball earth hypothesis,

a) earth was covered by ice at the end of the precambrian.

b) when the ice melted, life evolved rapidly.

c) the ediacara fauna evolved in the cambrian.

-->  d) all of these.

how did continents form during the precambrian?

-->  a) cratons converged with microcontinents and oceanic island arcs.

b) felsic minerals floated to the top of the magma ocean, then cooled.

c) the supercontinent pangaea broke apart.

d) all of these.

evidence for the breakup of rodinia includes

a) large mountain ranges where continents came together.

-->  b) large lava flows where continents rifted apart.

c) subduction zones where the continents rifted apart.

d) all of these.

the breakup of rodinia may have triggered snowball earth.

-->  a) true

b) false

precambrian plate tectonic processes after about 2 billion years after earth formed were

a) more like plate tectonics on venus than on the modern earth.

b) more like plate tectonics on the moon than on the modern earth.

-->  c) similar to modern plate tectonics.

d) much faster than modern plate tectonics.

only about 25% of the continental landmass present today was part of rodinia.

a) true

-->  b) false

the supercontinent rodinia contained all of the continents on earth before 2 billion years ago.

a) true

-->  b) false

the supercontinent of rodinia was complete when laurentia collided with rodinia.

-->  a) true

b) false

after rodinia broke apart, oceans formed between the continents by the process

-->  a) seafloor spreading.

b) subduction.

c) mountain building.

d) continental rifting.

diagram questions

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