Question

1. Which of the following gases was most likely present in Earth's earliest atmosphere? (1 point)

A) nitrogen
B) hydrogen
C) argon
D) oxygen

Answer 1

2. Which of the following statements accurately describes the development of the geologic time scale? (1 point)

A) Scientists developed the geologic time scale using fossilized remains from Europe and Asia.
B) Scientists developed the geologic time scale by studying rock layers and index fossils worldwide.
C) The geologic time scale was developed so scientists could put Earth's rocks in order by absolute age.
D) The geologic time scale was developed so geologists could describe short segments of time in Earth's history.

Answer 2

3. What can scientists learn from the rate at which radioactive elements decay? (1 point)
A) a rock's actual, or absolute, age
B) the relative age of rock layers
C) where one soil horizon ends and the next begins
D) the difference between molds and casts

4. The relative age of a rock is (1 point)
A) its age based on how much carbon- 14 it contains
B) its age compared with the ages of other rocks
C) less than the age of the fossils it contains
D) the number of years since it formed

Answer 3

hydrogen

Answer 4

5. After six half- lives, what percentage of a radioactive sample will remain? (1 point)
A) 0%-1%
B) 1%-3%
C) 3%-6%
D) 6%-10%

6. Earth's atmosphere, oceans, and continents began to form during the first several hundred million years of Precambrian time. (1 point)

A) true
B) false

Answer 5

7. Amold forms when minerals replace all or part of an organism. (1 point)
A) true
B) false


9 if the following graph represents the decay of strontium -90 in an igneous rock , what event occurred at 0 years on the horizontal axis ? 

(2point )

Answer 6

6- False
7- True

Answer 7

3- A