Earth Science Ch.12 Earth’s Evolution Through Geologic Time

The ________ period was a time of major extinctions, including 75 percent of amphibian families.

During the early Paleozoic era, South America, Africa, Australia, Antarctica, India, and perhaps China comprised the vast southern continent of ________.

The most common Precambrian fossils are ________, layered mounds of calcium carbonate.

During the ________ era, the westward-moving North American plate began to override the Pacific plate, eventually causing the tectonic activity that ultimately formed the mountains of western North America.

Earth's primitive atmosphere evolved from gases ________.

Mammals became the dominant land animals during the ________ era.

Which of the following gases was NOT part of Earth's original atmosphere?

In the early history of the earth, the solid surface of the earth weathered more rapidly than now because ________.

The major source of free oxygen in the atmosphere is from ________

One important reason we do not know much about the geologic history of the Precambrian is that ________.