Ice cores drilled from Greenland's glaciers provide amazing, direct, obvious, and seemingly irrefutable evidence that Creationists are just plain wrong. It's one of the coolest, and simplest, bits of evidence I've ever seen, and it utterly refutes Creationist's claims. It's hard to imagine a Creationist explanation of Greenland's ice cores that isn't an obvious farce.
Each year, a new layer of snow falls on Greenland, and the weight of the upper layers slowly compresses the lower layers into dense snow, hard-pack, and finally at a depth of 50 to 150 meters, into solid ice. These layers of ice are like a tree's rings, one layer per year. And here's the good part: The Greenland ice sheet is 2,000 to 3,000 meters thick and records almost 110,000 years of snowfall!
If that isn't enough, the first 12,000 years are visible to the naked eye, and beyond 12,000 years the annual layers are easily detectable by analytical tests.
Not convinced yet? It gets even better. Humanity's written history goes back a few thousand years, and records events like volcanic eruptions, dust storms and big climate changes. These events are captured in the ice as dust, pollen, and changes in oxygen isotope ratios (which are proportional to global temperatures). When we compare the story told by the ice, it matches our historical records exactly. In other words, there is independent proof that the Greenland ice sheet accurately records the Earth's history for thousands of years.
STILL not convinced? Well consider this: The only way the ice sheet's record could be interrupted is by gaps, not by insertions. You could imagine, for example, that a really warm summer melted a bunch of the snow, erasing the top layers. But if that happened, the bottom layers would be older, not younger, that an ice sheet without gaps.
And one last nail in the coffin of a Creationist explanation: Greenland's ice cores match Antarctica exactly. If you want to explain the layers as some sort of weird weather or catastrophic event, you have to claim that the exact same event happened in two places, almost half way around the world from each other, at the exact same times, over and over again to create 110,000 layers of ice that exactly match.
Ok, creationists, how do you explain 110,000 years of ice accumulation in Greenland?