Podcast
Questions and Answers
What percentage of Earth's surface is covered by oceans?
What percentage of Earth's surface is covered by oceans?
- 90 percent
- 50 percent
- 80 percent
- 70 percent (correct)
What is the average salt content of ocean water?
What is the average salt content of ocean water?
- 35 parts per thousand (correct)
- 50 parts per thousand
- 20 parts per thousand
- 70 parts per thousand
How much salt per cubic mile of seawater is there in the ocean?
How much salt per cubic mile of seawater is there in the ocean?
- 150 million tons
- 100 million tons
- 120 million tons (correct)
- 50 million tons
What causes rain to become slightly acidic as it forms and falls through the air?
What causes rain to become slightly acidic as it forms and falls through the air?
How does ocean water accumulate salt and other dissolved minerals?
How does ocean water accumulate salt and other dissolved minerals?
Edmond Halley suggested that the salinity of seawater could serve as a kind of ______ that could be used to determine the age of the ocean
Edmond Halley suggested that the salinity of seawater could serve as a kind of ______ that could be used to determine the age of the ocean
John Joly came up with an estimate of 90 million years for the age of the ocean using Halley's ______
John Joly came up with an estimate of 90 million years for the age of the ocean using Halley's ______
Halley reasoned that dividing the total volume of ocean water by the rate at which salt was deposited in the ocean would show how long it had taken for the ocean to reach its current level of ______
Halley reasoned that dividing the total volume of ocean water by the rate at which salt was deposited in the ocean would show how long it had taken for the ocean to reach its current level of ______
More-advanced techniques later revealed the estimate of 90 million years to be a major ______
More-advanced techniques later revealed the estimate of 90 million years to be a major ______
Halley had failed to account for the fact that some sea salt becomes ______
Halley had failed to account for the fact that some sea salt becomes ______
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Study Notes
Salt Deposition in the Sea
- In 1715, British astronomer Edmond Halley proposed that salt was gradually deposited in the sea by rivers.
- Halley suggested that the salinity of seawater could be used as a clock to determine the age of the ocean and, by extension, the Earth.
- He proposed that dividing the total volume of ocean water by the rate of salt deposition would reveal the time it took for the ocean to reach its current level of salinity.
Early Estimation of the Ocean's Age
- In 1899, Irish physicist John Joly attempted to calculate the age of the ocean using Halley's method.
- Joly estimated the age of the ocean to be around 90 million years.
- Later, more advanced techniques revealed that this estimate was a major underestimate, and the actual age of the ocean is around four billion years.
Flaws in Halley's Scheme
- Halley's method had a significant flaw: it failed to account for the sequestration of some sea salt.
- This oversight compromised the accuracy of Halley's proposed method for determining the age of the ocean.
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