Earth Atmosphere Quiz

The very first Earth atmosphere, forming with Earth itself, was probably dominated by the cosmically abundant gases _______ and _______.

• nitrogen; oxygen

• hydrogen; helium

• carbon dioxide; methane

• water vapor; sulfur dioxide

Answer explanation

The very first atmosphere of Earth was likely composed of hydrogen and helium, as these are the most abundant elements in the universe. Other gases like nitrogen and oxygen became prevalent later due to biological processes.

Which two gases are most abundantly emitted in volcanic outgassing?

• nitrogen and oxygen

• hydrogen and helium

• carbon dioxide and methane

• water vapor and sulfur dioxide

Answer explanation

Volcanic outgassing primarily releases water vapor and sulfur dioxide. These gases are produced during magma formation and eruption, making them the most abundant emissions from volcanoes.

The long-term buildup of oxygen in Earth’s atmosphere is a result of _______.

• volcanic outgassing

• photosynthesis

• limestone formation in the ocean

• solar radiation splitting molecules of ozone in the stratosphere

Answer explanation

The long-term buildup of oxygen in Earth’s atmosphere is primarily due to photosynthesis, a process where plants convert carbon dioxide and water into glucose and oxygen, significantly increasing atmospheric oxygen levels.

Which two gases are most important in producing the greenhouse effect on Earth?

• nitrogen and oxygen

• hydrogen and helium

• carbon dioxide and methane

• nitrogen and sulfur dioxide

Answer explanation

Carbon dioxide and methane are the primary greenhouse gases that trap heat in the atmosphere, significantly contributing to the greenhouse effect. Other gases like nitrogen and oxygen do not have this effect.

According to geological evidence and computer models based on that evidence, which statement about the concentration of oxygen in our atmosphere is correct?

• No oxygen was present prior to the Cambrian Era; oxygen levels have uniformly risen since, and today’s atmosphere is more oxygen rich than at any time in Earth’s history.

• Oxygen levels were greatest during the Cambrian Era but have been steadily declining ever since; today’s atmosphere is less oxygen rich than at any time in Earth’s history.

• Oxygen levels have generally risen during the Phanerozoic Era but peaked during the Mesozoic Era (Age of Dinosaurs) and declined sharply in the Early Cenozoic Era.

• Oxygen levels have generally risen during the Phanerozoic Era but peaked during the Late Paleozoic Era (the time of coal swamp forests) and declined sharply in the Early Mesozoic Era.

Answer explanation

Oxygen levels rose during the Phanerozoic Era, peaking in the Late Paleozoic Era due to extensive coal swamp forests, then sharply declined in the Early Mesozoic Era, making this statement the correct one.

Consult the figure below. During which period of Earth’s history was the oxygen saturation in the atmosphere highest?

• Cambrian Era

• Mesozoic Era

• Late Paleozoic Era

• Early Cenozoic Era

Answer explanation

The Late Paleozoic Era saw the highest levels of atmospheric oxygen, reaching up to 35%. This period was characterized by extensive plant life, which contributed significantly to oxygen production.

Which two gases are most abundant within Earth’s modern atmosphere?

• nitrogen and oxygen

• hydrogen and helium

• carbon dioxide and methane

• water vapor and sulfur dioxide

Answer explanation

Earth's modern atmosphere is primarily composed of nitrogen (about 78%) and oxygen (about 21%). Other gases like hydrogen, helium, carbon dioxide, and methane are present in much smaller amounts.

As an air mass rises, it generally experiences _______.

• an increase in pressure

• a decrease in pressure

• no change in pressure

• either an increase or a decrease in pressure, depending on temperature

Answer explanation

As an air mass rises, it encounters lower atmospheric pressure due to the decrease in weight of the air above it. Therefore, the correct answer is 'a decrease in pressure'.

As an air mass rises, it generally experiences _______.

• a decrease in temperature because of adiabatic cooling

• an increase in temperature because of adiabatic heating

• an increase in temperature because of increasing proximity to the Sun

• an increase in pressure due to higher altitude

• no change in temperature

Answer explanation

As an air mass rises, it expands and cools due to lower pressure at higher altitudes, leading to a decrease in temperature through a process known as adiabatic cooling.

To an observer traveling outward from Earth’s surface into outer space, the temperature of the atmosphere _______.

• uniformly decreases because of atmospheric thinning

• uniformly increases because of increasing proximity to the Sun

• remains relatively constant until the very edge of the atmosphere, where the observer would experience the very cold vacuum that is interplanetary space

• decreases, stabilizes, increases, stabilizes, decreases, stabilizes, and, finally, increases until the edge of the atmosphere is reached

Answer explanation

As an observer moves outward, the temperature first decreases due to thinning atmosphere, then stabilizes, and can increase slightly in certain layers before decreasing again, reflecting the complex temperature profile of the atmosphere.