Earth Science Chapter 22 The Precambrian Earth

In early life, mainly the ___ modified atmosphere by making large amounts of the gas that formed the ozone layer

mat or mound composed of billions of cyanobacteria

As a result of meteorite bombardment of Earth, the size and temperature of Earth __

A major extinction occured near the end of the Proterozoic, in which widespread __ may have played a critical role

Early in the Proterozoic, _____ began to collide as a result of plate tectonics

building blocks of proteins

Proterozoic ends 542 mya

The oldest rock samples collected from the Moon are approximately 4.4 to 4.5 ___ years old

tiny, threadlike photosynthetic organisms

single celled organisms without a nucleus are called

deepest, most stable part of a continent

How do the ages of Earth and Moon compare

The buried and exposed part of a continental shield together compose the ____, the stable core of a continent

hot water vent at volcanic seafloor rift

Earth's earliest ___ likely formed as a result of the cooling of the uppermost mantle

stable mineral that commonly occurs in granite

As the molten magma of early Earth cooled, ___ minerals remained near Earth's surface

The chemicals and hot water present at ____ have been demonstrated to form amino acids

fossils of soft-bodied Proterozoic organisms

Earth's early atomosphere likely contained large concentrations of watervapor, nitrogen and __ gases from volcanoes

Banded iron formations demonstrate that the atmosphere contained oxygen by the early ____

What was Earth's earliest crust like?