Air from Another Age
Written by Studio AM.
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Snow that falls on central Antarctica may remain instead of melting. Later snow buries it, pressure turns it into ice, and closing pores trap samples of the surrounding air. A bubble is not labeled with a year, but it preserves gases from an atmosphere far older than any instrument record.
In an undisturbed sequence, deeper layers are generally older than the ice above them. Earlier Antarctic cores produced a continuous climate record reaching about eight hundred thousand years. In January 2025, the Beyond EPICA team reported that its Little Dome C core reached at least 1.2 million years. Establishing the age of the deepest ice requires several kinds of evidence.
Two kinds of evidence come from a core. Air bubbles let researchers measure gases such as carbon dioxide and methane. The ice itself holds indirect temperature clues. Ratios of heavier and lighter forms of oxygen and hydrogen vary with the conditions in which snow formed.
The gas record and the temperature clues do not share exactly the same age at a given depth: air is sealed only after snow has already begun becoming ice. Scientists model that age difference and compare several dating clues. An ice core is a valuable archive of several physical records. Comparing them helps researchers reconstruct past conditions.
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Questions
Choose an answer. The explanation appears after you answer.
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Question 1 of 4
What is the main idea of the passage?
The answer is A: Ice preserves old gases and climate clues that must be dated carefully.
The passage describes the two records, the new reach, and the dating work required to compare them.
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Question 2 of 4
What age did the Beyond EPICA team report for the Little Dome C core in January 2025?
The answer is B: At least 1.2 million years
The second paragraph gives the team's January 2025 report: the core reached at least 1.2 million years.
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Question 3 of 4
Before comparing a gas change with a temperature change at the same depth, what must researchers consider?
The answer is C: Whether the trapped air and the surrounding ice have different ages.
The air was trapped after the snow began forming ice. A shared depth does not automatically mean the gas and temperature clues describe the same time.
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Question 4 of 4
In the last paragraph, “archive” means
The answer is D: a store of records preserved for later study
The core preserves several kinds of evidence for researchers to study. That makes 'archive' a useful comparison.
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