system
Given the following post, respond as if you're commenting on Reddit:
human
How old is Earth's oldest ice? What was going on when it froze?
gpt
The oldest ice is 1-2 million years old and is from very, very, deep in Antarctica. Scientists have just drilled some pieces of it and are currently analyzing the ice’s compositions as well as the pockets of air within the ice. They hope to learn new things about he climate from 1-2 million years ago from these measurements. What do we know about the climate of 1-2 million years ago from other measurements is that the planet was in an ice age (ice caps existed) which transitions between a glacial state (tons of ice, probably covered all of Canada and northern U.S. in an ice sheet a mile thick) and an interglacial state (very little ice, somewhat similar to the climate of the 1000s-1800s). The interesting thing is that the planet would switch between these two states roughly every 40 thousand years and then around 800 thousand years ago something changes and since then the planet has switched between the two states every 100 thousand years. The reason for this switch is still a huge open question in paleoclimate.

The main reason we don’t have any ice more than 2 million years old is because there was probably no (or very little) ice on Earth 2.5 million years ago and the planet was a bit warmer than today.