We Never Know
No Slack
At the end of the last Ice Age, the mountains were covered with water in the form of large glacial lakes caused by melting glaciers. (Lake Missoula is the one that was in my area of the earth. When the ice dam floodgates were breached, it let loose a deluge that left huge scars over vast areas of land that can be seen today.)
We are still coming out of the last ice age to my underdtanding....
"Like all the others, the most recent ice age brought a series of glacial advances and retreats. In fact, we are technically still in an ice age. We’re just living out our lives during an interglacial."
What's the coldest the Earth's ever been?.