Page 109 - Science Course 1 (Book 2)
P. 109
Mo9-L3a: What is the Origin of Earth’s Atmosphere?
Origins of Earth’s Atmosphere As Earth and its atmosphere cooled, the water vapor
condensed into liquid, rain fell, and then evaporated
from Earth’s surface for thousands of years.
Erupting volcanoes emitting hot gases from ancient
Earth’s interior surrounded the planet to form an Eventually water began to accumulate on Earth’s
atmosphere. surface, forming oceans.
Ancient Earth’s atmosphere was thought to be water Earth’s f rst organisms could undergo photosynthesis,
vapor with a little carbon dioxide and nitrogen, but which changed the atmosphere.
not enough oxygen to support life.
Water vapor is water in gaseous form.
The organisms removed Co² from the atmosphere and released oxygen into it.
Eventually the levels of Co² and oxygen supported the development of other organisms.
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