How do geologists determine the composition of Earth's interior? ...

[bobbysung]

How do geologists determine the composition of Earth's interior? Why not examine it directly?
 
  What will be an ideal response?

Question 2

Approximately what percent of geologic time is represented by the Precambrian? Which period within the Phanerozoic eon represents the longest interval of time? How long is it?
 
  What will be an ideal response?

[juiceman1987]

Answer to Question 1

Energy from earthquakes allows scientists to model its composition. The distance and temperatures are too great to penetrate deep into much of Earth's lithosphere, let alone the rest of the planet.

Answer to Question 2

3958 out of 4500 million years which is approximately 3958/4500 or 88; Cretaceous Period 145 -65 = 80 million years.

[bobbysung]

Correct answers!

[juiceman1987]

Great! Please up vote