Chapter Quiz

[1] The Earth probably had an atmosphere before the Sun was fully formed. This primitive atmosphere was possibly composed principally of hydrogen and helium, the two most abundant gases in the universe, along with a few simple compounds such as ammonia and methane. Then when the temperature and pressure in the contracting center of the still-forming Sun became high enough to ignite thermonuclear reactions, our Sun was born. The blast from the Sun’s formation must have produced a strong outflow of charged particles—an outflow strong enough to sweep the Earth of its earliest atmosphere.

[2] The next stage in the formation of the atmosphere likely occurred when gases trapped in the Earth’s hot interior escaped through volcanoes and fissures at the Earth’s surface. The gases spewed out by these early eruptions were probably much like the gases found in the volcanic eruptions of today—about 85 percent carbon dioxide, and 5 percent nitrogen, by mass. The early atmosphere had no free oxygen and therefore was inhospitable to the type of life we have today. The production of free oxygen did not occur until the primitive plants known as stromatolites and green algae appeared. Stromatolites and green algae, like all green plants use photosynthesis to convert carbon dioxide and water to hydrocarbon and free oxygen. With the production of free oxygen, an ozone (O3) layer formed in the upper atmosphere. The ozone layer acts like a filter to reduce the amount of ultraviolet radiation reaching the Earth’s surface. The surface therefore became more hospitable to life. The evolution of oxygen in this global envelope was a vital step in the history of Earth and its life.

[3] As the Earth cooled, the rich supply of water vapor condensed to form the oceans. Comet debris from interplanetary space also contributed water to the oceans. These oceans, essential to the evolution of life and ultimately to the development of the present global environment, have remained for the rest of the Earth’s history.

Source: Hewitt, P.G., Suchocki, J., & Hewitt, L.A. (1999). Conceptual Physical Science, 2/e., New York, © Paul G. Hewitt, John Suchocki, and Leslie A. Hewitt. An imprint of Addison Wesley Longman, pp. 642-644.

This activity contains 10 questions.

	Within the question text below, there is one text entry field where you can enter your answer. It is believed that even before the Sun was formed that the Earth had a(n) .

	Within the question text below, there is one text entry field where you can enter your answer. The two most abundant gases in the universe are helium and .

	Within the question text below, there is one text entry field where you can enter your answer. Scientists think that the primitive atmosphere was made up mainly of hydrogen and .

	Within the question text below, there is one text entry field where you can enter your answer. The primitive atmosphere also contained smaller amounts of simple compounds such as methane and .

	Within the question text below, there is one text entry field where you can enter your answer. Scientists speculate that the Earth's earliest atmosphere was changed by the blast of the formation.

	Within the question text below, there is one text entry field where you can enter your answer. Our Sun was created from a series of reactions.

	Within the question text below, there is one text entry field where you can enter your answer. The gases trapped in the Earth's interior escaped through volcanoes and fissures. Scientists believe these gases were approximately 85 % carbon dioxide and 5 % .

	Within the question text below, there is one text entry field where you can enter your answer. The early atmosphere could not sustain life because it had no free .

	Within the question text below, there is one text entry field where you can enter your answer. The ozone layer was important to the development of life on Earth because it acted like a filter to reduce the amount of reaching the Earth’s surface.

	Within the question text below, there is one text entry field where you can enter your answer. The Earth's oceans originated from water vapor and .

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