Why are the Archean and Proterozoic Eras not divided into smaller units like the Cenozoic Era?

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Answer: This part of Earth's history is commonly called the Precambrian. The Precambrian occurred so long ago (4 billion years before the Cambrian) that not much detail is known from this time. The further back in the rock record/time you look, the more fragmented the record and clues become.

Environmental & Atmospheric Sciences

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Judge the following sentence according to the criteria given below: Waves break in the surf zone BECAUSE particle motion near the bottom of the wave is severely restricted

A) The assertion and the reason are both correct, and the reason is valid. B) The assertion and the reason are both correct, but the reason is invalid. C) The assertion is correct, but the reason is incorrect. D) The assertion is incorrect, but the reason is correct. E) Both the assertion and the reason are incorrect.

Environmental & Atmospheric Sciences

Which of the following controls the ocean's conveyor belt circulation?

A. gradients in algae concentration B. gradients in particulates concentration C. gradients in water salinity D. gradients in water turbidity

Environmental & Atmospheric Sciences

Increase the transparency of the lahar layers so you can see the terrain underneath. What terrain features appear to control the flow of the lahars?

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Environmental & Atmospheric Sciences

Why does the chapter suggest that it would be easier for Oprah to give up eating hamburgers than to give up driving cars?

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Environmental & Atmospheric Sciences