1. Scientists infer that most of Earth's earliest atmosphere was produced by (1) a collision with a giant gas cloud
(2) capturing gases from a nearby planet
(3) vaporizing comets that impacted Earth's surface
(4) the escape of gases from Earth's molten surface
2. What percentage of Earth's history represents human existence?
(1) less than 1.0% (2) 1.8%
(3) 23.5%
v
(4) more than 98.6%
3. During which period in geologic history did the uplifting of the Adirondack Mountains begin?
(1) Quaternary
(2) Cretaceous (3) Triassic
(4) Cambrian
4. The graph below shows the decay of a radioactive material over time.