SciolyHarsh wrote:Hey guys, so I'm stuck on a question for a practice test, and I don't understand why the answer is wrong.
What do ice cores preserve that allow us to understand more about past climates?
a) They show the granular composition of the snow at the time, which shows the terrestrial elements most prevalent during that period
b) They capture debris that reflects the sedimentary elements on the surface at the time
c) They capture atmospheric air when they are formed, reflecting the air quality at the time
d) Their radioactivity makes it easy to capture information on the history of the ice core.
My answer was c, but the correct answer is d. Could you guys explain why?
They definitely have atmospheric air of that time period, but what we are truly focusing on is I believe the O-18 to O-16 ratios. Since O-18 is an unstable isotope (the neutron:proton ratio is greater than 1, so it is unstable and thus radioactive for a quick explanation), it does undergo decay over a period of time, and that's why it would say that it is radioactivity. Over time the O-18 will experience numerous half-lives, and we essentially use the half-life data to calculate the age and history of the ice core. We aren't really looking into the composition of air directly, we look more for just those specific oxygen isotopes to understand this. Correct me if I am wrong, but I believe that's why it is d).