KKKK - Earth: Geology, Atmosphere, Radioactive Dating
The “Carbon cycle” is a mechanism of Earth’s geology that processes Carbon in various forms, moving it from our atmosphere to our oceans, to the crust and back up into the atmosphere.
(a) How does the Carbon cycle help Earth avoid the fate of Venus, which suffers from an intense greenhouse effect that makes the surface incredibly hot?
(b) How are we affecting the Carbon cycle?
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All four of the terrestrial planets (Mercury, Venus, Earth and Mars) have significant cores of iron. Taking Earth/Venus as an example, explain why the iron in the Earth/Venus is concentrated mostly in the core instead of being evenly distributed throughout the entire Earth/Venus?
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In radioactive dating, we measure the abundance of a parent and daughter element to see what fraction of the parent has decayed into daughter atoms. Explain how we know how much of each kind of atom (parent and daughter) was present when the rock initially solidified.
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We know that when a certain rock formed, it contained half as many parent atoms as stable sibling atoms. The parent atoms have a half-life of 500 years. Today, the rock has 10 parent atoms, 120 daughter atoms and 160 sibling atoms. State how long ago the rock formed and what its initial composition was (number of parent, daughter and sibling atoms). Show your work!
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The half-life of a given parent element, X, is 1000 years. It decays into daughter element Y. At present, a given rock consists of 1% X and 7% Y (the other 92% is not important).
By analyzing the stable isotopes of the daughter element, we know that the object originally contained 4% of the daughter element, Y. How old is this rock? Show/explain your work.
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The half-life of a given parent element, X, is 100 years. It decays into daughter element Y. At present, a given rock consists of 1% X and 15% Y (the other 84% is not important).
By analyzing the stable isotopes of the daughter element, we know that the object originally contained 8% of the daughter element, Y. How old is this rock? Show/explain your work.
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The half-life of a given parent element, X, is 1000 years. It decays into daughter element Y. At present, a given rock consists of 2% X and 14% Y (the other 84% is not important).
By analyzing the stable isotopes of the daughter element, we know that the object originally contained 8% of the daughter element, Y. How old is this rock? Show/explain your work.
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A certain rock forms with 16 parent atoms, 16 daughter atoms and 16 stable sibling atoms. The parent atoms have a half-life of 100 years. What will be the composition of the rock after 300 years have passed? Show your work!
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The crater retention age of the Earth’s surface is much lower (in the other words, the surface of the Earth has far fewer craters) than either the lunar maria or the lunar highlands.
a) (6 pts) Explain the concept of “crater retention age”, and as part of your explanation, state whether the statement above implies that the Earth’s surface is older than or younger than the lunar maria and the lunar highlands.
b) (6 pts) What is happening within the Earth that makes Earth’s crater retention age so different from that the the lunar maria and highlands?
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We know that when a certain rock formed, it contained twice as many parent atoms as stable sibling atoms. The parent atoms have a half-life of 200 years. Today, the rock has 5 parent atoms, 45 daughter atoms and 20 sibling atoms. State how long ago the rock formed and what its initial composition was (number of parent, daughter and sibling atoms). Show your work!
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In order to determine the date of formation of a portion of the lunar surface, scientists brought back a variety of rocks for radioactive dating. One particular rock contained 15/20 parent atoms, 255 daughter atoms and 75 sibling atoms. We know that when the rock formed, it had half as many sibling atoms as daughter atoms. The parent atoms have a half life of 1 billion years. How old is the rock, and what was the original number of parent, daughter and sibling atoms?
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A given rock from a planetary surface contains 30 parent elements, 500 daughter elements and 50 stable siblings. We know that the half life of the parent element is 100 million years. We also know that when this sort of rock solidifies from a molten state, the number of daughter atoms is equal to the number of stable sibling atoms.
a) (4 pts) Explain why rocks with extremely old solidification ages (upwards of a billion years or so) are not found often on the Earth, even though the Earth has an estimated age of 4.5 billion years.
b) (10 pts) What is the solidification age of this rock, and what was the rock's original composion of parents, daughters and stable siblings? Show your work.
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A given rock from a planetary surface contains 80 parent elements, 400 daughter elements and 320 stable siblings. We know that the half life of the parent element is 1 billion years. We also know that when this sort of rock solidifies from a molten state, the number of daughter atoms is equal to one half the number of stable sibling atoms.
a) (4 pts) Explain why rocks with extremely old solidification ages (upwards of a billion years or so) are not found often on the Earth, even though the Earth has an estimated age of 4.5 billion years.
b) (10 pts) What is the solidification age of this rock, and what was the rock's original composion of parents, daughters and stable siblings? Show your work.
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A given rock from a planetary surface contains 25 parent elements, 775 daughter elements and 200 stable siblings. We know that the half life of the parent element is 100 million years. We also know that when this sort of rock solidifies from a molten state, the number of daughter atoms is equal to twice the number of stable sibling atoms.
a) (4 pts) Explain why rocks with extremely old solidification ages (upwards of a billion years or so) are not found often on the Earth, even though the Earth has an estimated age of 4.5 billion years.
b) (10 pts) What is the solidification age of this rock, and what was the rock's original composion of parents, daughters and stable siblings? Show your work.
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Over the past few billion years, the overall light intensity of the Sun has increased by about 20%.
a) (6 pts) How has the average surface temperature of the Earth changed during that time (warmed, cooled, stayed about the same)? Explain why it has or hasn't changed.
b) (8 pts) Aside from the increased amount of sunlight on the Earth, we have had a couple of other important internal heat sources in the past. Name and explain two of them.
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We know that when a certain rock formed, it contained half as many stable sibling atoms relative to radioactive parent atoms. The half life of the radioactive parent atoms in the rock is 40,000 years. The current composition of the rock is 10 parent atoms, 240 daughter atoms and 40 stable sibling atoms. How long ago did this rock solidify, and what was the original composition of this rock (number of parents, daughters and siblings) when it solidified?
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Aurorae are beautiful patterns of light emission that tend to occur at high Northern and Southern latitudes on the Earth.
a) (6 pts) Describe what causes the gases in Earth’s atmosphere to glow this way.
b) (6 pts) Why do aurorae only appear at high latitudes? A diagram may help.
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The absence of liquid water on Venus is a crucial component to the process that warmed the planet up to its current extremely hot temperature. What role does liquid water play in the Carbon cycle on Earth and how does its absence lead to global warming?
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What two properties does Earth’s atmosphere have that keep us from losing our water the way Venus did during the runaway greenhouse phase of its evolution? Explain.
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Tiny bubbles trapped in frozen ice tell us that billions of years ago, Earth’s atmosphere had much more Carbon Dioxide than it has today.
a) (6 pts) Why, then, was the temperature at that time about the same as it is today instead of being a lot warmer? Explain.
b) (6 pts) What changed on Earth over time that caused the level of Carbon Dioxide in our atmosphere to decrease? Explain.
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Explain what causes aurorae. As part of your answer, explain why people on the Earth’s equator are unlikely to witness these spectacular phenomena.
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The Earth’s original atmosphere contained three noble gases, Helium (mass = 2), Neon (mass = 10) and Argon (mass = 18).
a) (6 pts) Today, Earth retains the Neon and Argon gases but not the Helium gas. Explain why the Neon and Argon are retained while Helium is not (just a simple equation is insufficient...you need to explain where the equation comes from).
b) (6 pts) If Earth were to heat up substantially due to the greenhouse effect, we would probably be unable to retain Neon gas (but Argon gas would still have a larger chance of being retained). Explain why a rise in temperature might make it possible for Earth to lose its Neon gas.
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Long-term and short-term changes in the Carbon Dioxide content of our atmosphere may be responsible for climate changes on the Earth. Give an example of a source and a sink of Carbon Dioxide in our atmosphere, and briefly state why human emissions of Carbon Dioxide, despite being insignificant compared to a typical volcanic eruption, are currently driving CO2 levels to double or triple within a few decades.
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Though our atmosphere has undergone many changes lately, one gas has had an abundance that has remained relatively stable over long periods of time: Argon.
a) (6 pts) Name and briefly explain two reasons why the abundance of Argon doesn't change in the Earth's atmosphere.
b) (8 pts) One molecule that has changed a lot is ozone, particularly over the Antarctic. Name and briefly explain *two* reasons why ozone depletion in the stratosphere occurs largely over the south pole rather than over the northern hemisphere, which is where most of the ozone depleting chemicals are manufactured and used.
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When a certain rock solidifies, the number of daughter atoms is typically equal to one-half the number of stable isotope siblings. The half-life of the parent element is 5,000 years. The current composition of the rock is 30 Parents, 530 Daughters and 160 Stable Siblings. What is the age and original composition of the rock? SHOW ALL WORK.
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When a certain rock solidifies, the number of parent atoms is typically equal to twice the number of stable isotope siblings. The half-life of the parent element is 8,000 years. The current composition of the rock is 30 Parents, 530 Daughters and 120 Stable Siblings. What is the age and original composition of the rock? SHOW ALL WORK.
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Auroral light can often be seen in the night sky at certain latitudes on the Earth. Most of the light given off comes from forbidden spectral lines of Oxygen and Nitrogen.
a) (3 pts) Briefly explain what causes aurorae and why they are only seen at very high latitudes (in the north or the south).
b) (5 pts) Explain why forbidden spectral lines can only be seen in very low density gases (such as the upper atmosphere of the Earth).
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The Earth's early history is difficult to study, but we do have some clues that tell us what conditions were like long ago.
a) (6 pts) We know that Argon gas was part of the Earth's original atmosphere. Name and explain the two properties of Argon that make it possible for Argon to stick around unchanged in the atmosphere for so long.
b) (8 pts) We know that water was present on the Earth's surface from almost the very beginning. What geological evidence (related to zircon crystals) tells us this?
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Suppose we were to take a planet like the Earth (with its current mass, size and atmospheric composition) and move it extremely close to the Sun, where it is much hotter.
a) (7 pts) In this situation, the atmosphere would be more likely to escape. Explain why.
b) (7 pts) The gases that will escape the easiest would be molecular Nitrogen (mass = 28) and molecular Oxygen (mass = 32) rather than the more massive Argon (mass = 40) and Carbon Dioxide (mass = 44). Explain why this is true. A simple equation showing a proportionality is not a sufficient answer. You need to explain why.
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A given rock from a planetary surface contains 25 parent elements, 775 daughter elements and 200 stable siblings. We know that the half life of the parent element is 100 million years. We also know that when this sort of rock solidifies from a molten state, the number of daughter atoms is equal to twice the number of stable sibling atoms.
a) (4 pts) Explain why rocks with extremely old solidification ages (upwards of a billion years or so) are not found often on the Earth, even though the Earth has an estimated age of 4.5 billion years.
b) (10 pts) What is the solidification age of this rock, and what was the rock's original composion of parents, daughters and stable siblings? Show your work.
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Studying the nature of the Earth's interior can tell us a lot about the Earth's past, even conditions shortly after the Earth formed.
a) (8 pts) Describe the evidence that led scientists to believe the continents were all clustered around equatorial latitudes during the geological era 600 million years ago.
b) (6 pts) Describe the evidence that tells us the Earth was originally in a liquid (or molten) state shortly after its formation.
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In a certain rock, we know that when the rock first solidified, the number of parent atoms present in the rock was equal to four times the number of stable siblings. The half-life of the parent atom is 2 million years. The current composition of the rock is 30 parents, 510 children and 60 stable siblings.
What is the age and original composition of the rock? Show all work.