Author Question: Why do we know very little about the planet's first 600 million years? Why do we know only slightly ... (Read 35 times)

ahriuashd · **on:** Jul 15, 2018

Why do we know very little about the planet's first 600 million years? Why do we know only slightly
more about the early part of the Precambrian? What will be an ideal response?

Question 2

Describe the beginning of operations of Earth's systems and when that occurred. What will be an ideal response?

juwms · **Reply #1 on:** Jul 15, 2018

Answer to Question 1

No rocks are known for the first 600 million years of geologic time. Although there are rocks
beginning at 4.0 billion years, these rocks are difficult to decipher because they have been
metamorphosed and complexly deformed, they are buried beneath younger rocks, and they contain few
fossils useful for determining relative ages

Answer to Question 2

Earth formed around 4.6 billion years ago, but it was not as we see it today. Differentiation into core
and mantle happened millions of years after formation, and no crust is now seen that is older than 4.0
billion years. After differentiation, plate tectonics began, although initially perhaps different from the
way it is today. By 3.5 billion years ago, Earth's systems were fully operative and interacting much as
they do today.