1. Why was there liquid water on early Earth (4 billion years ago) even though t
ID: 290406 • Letter: 1
Question
1.
Why was there liquid water on early Earth (4 billion years ago) even though the sun was 30% less luminous than it is today?
Early Earth had more greenhouse gases in the atmosphere than today.
Early Earth had a lower albedo compared to today.
Early Earth had less nitrogen in the atmosphere when compared to today.
Early Earth had more geothermal energy and volcanoes compared to today.
2.
How can we tell that the currently increased carbon dioxide in the atmosphere is due to burning fossil fuels?
13C/12C ratios (?13C) in the atmosphere are increasing because fossil fuel comes from old plant material
13C/12C ratios (?13C) in the atmosphere are increasing because fossil fuel has a high 13C content
13C/12C ratios (?13C) in the atmosphere are decreasing because fossil fuel is old plant material
none of the aboive
3.
Since 50 million years ago, Earth has been generally
cooling, due to plate tectonics and decreased volcanism
warming, due to plate tectonics and decreased volcanism
cooling, due to increasing solar radiation
warming, due to increasing solar radiation
What does the figure above, showing planktonic ?18O from a marine sediment core, tell us about the climate changes going on around 55 million years ago (in the period marked by the red bar)? While not shown, assume that benthic ?18O from a marine sediment core shows no change during the period marked by the red bars.
Ice volume decreased
Ice volume increased
The temperature decreased
The temperature stayed the same
The temperature increased
What do the measurements of ?13C from a marine sediment core shown above tell us about what caused the PETA (Paleocene-Eocene Thermal Anomaly) shortly after 55 million years ago?
There was an increase in ?13C, suggesting the injection of plant-based carbon into the atmosphere (e.g., from fossil fuels)
There was an increase in ?13C, suggesting there were was less 12C carbon in the atmosphere/ocean due to reduced biological activity.
A large meteorite impact changed the atmospheric CO2 composition
A large cooling of the atmosphere/ocean system occurred
There was a decrease in ?13C, suggesting the injection of plant-based carbon into the atmosphere (e.g., from fossil fuels)
AEarly Earth had more greenhouse gases in the atmosphere than today.
BEarly Earth had a lower albedo compared to today.
CEarly Earth had less nitrogen in the atmosphere when compared to today.
DEarly Earth had more geothermal energy and volcanoes compared to today.
4 5 4 5 5 5 .5 0 2 (9%) 08,9Explanation / Answer
Ans 1)
Early Earth had more greenhouse gases in the atmosphere than today.
When it first formed, Earth's atmosphere may have contained more greenhouse gases. Carbon dioxide, Methane, Carbonyl Sulphide etc predominated and their collective greenhouse effect would have been sufficient to prevent Earth from freezing over.
Ans 2)
13C/12C ratios (?13C) in the atmosphere are decreasing because fossil fuel is old plant material
CO2 produced from burning fossil fuels or burning forests has quite a different isotopic composition from CO2 in the atmosphere. This is because plants have a preference for the lighter isotopes (12C vs. 13C); thus they have lower 13C/12C ratios. Since fossil fuels are ultimately derived from ancient plants, plants and fossil fuels all have roughly the same 13C/12C ratio – about 2% lower than that of the atmosphere. As CO2 from these materials is released into, and mixes with, the atmosphere, the average 13C/12C ratio of the atmosphere decreases.
Ans 3)
cooling, due to plate tectonics and decreased volcanism
Greenhouses gases like CO2 are so named for their ability to magnify the sun’s energy, and 50 million years ago the sun wasn’t as hot— our star is getting hotter with age. During the Eocene, it took more atmospheric CO2 to influence temperatures than it does today. With our present carbon emissions, it is predicted that by 2100, Earth's temperature will rise up to what it was around 50 million years ago.
Ans 4)
The temperature increased
The shells of tiny plants and animals and corals are typically made of calcium carbonate (CaCO3), which is the same as limestone, or chalk, or silicon dioxide (SiO2), similar to the compound common in quartz sand. As the shells form, they tend to incorporate more heavy oxygen than light oxygen, regardless of the oxygen ratio in the water. The biological and chemical processes that cause the shells to incorporate greater proportions of heavy oxygen become even more pronounced as the temperature drops, so that shells formed in cold waters have an even larger proportion of heavy oxygen than shells formed in warmer waters. There is a prominent (>1‰) negative excursion in the ?18O of foraminifera shells, both those made in surface and deep ocean water. Because there was a paucity of continental ice in the early Paleogene, the shift in ?18O very probably signifies a rise in ocean temperature.
Ans 5)
There was a decrease in ?13C, suggesting the injection of plant-based carbon into the atmosphere (e.g., from fossil fuels)
A prominent negative excursion in the carbon isotope composition (?13C) of carbon-bearing phases characterizes the PETM in numerous (>130) widespread locations from a range of environments. The onset of the Paleocene–Eocene Thermal Maximum has been linked to an initial 5 °C temperature rise and to extreme changes in Earth's carbon cycle. The period is marked by a prominent negative excursion in carbon stable isotope (?13C) records from around the globe; more specifically, there was a large decrease in 13C/12C ratio of marine and terrestrial carbonates and organic carbon.
AEarly Earth had more greenhouse gases in the atmosphere than today.
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