This week's Fiction Writers Group flash fiction prompt is https://pixabay.com/photos/sunset-tree-dawn-sun-nature-dusk-3156440/:
My take on it is "The Last Tree":
The Last Tree
It's not that the water rose. Oh, it did. Don't get me wrong. New York, Boston, Philly, all the way down the East coast. Most of Florida was under water. The West coast, too. But their mountains are much closer to the sea there. The inundation there was more localized, but much deeper.
That's what the melting of the ice caps did. Bad enough, but it didn't stop there. The oceans crept further inland. Relentlessly. The climatologists were stumped. There ice was gone, so where was the water coming from?
It was the geologists who provided the answer. It turned out the water wasn't rising. The ground was falling. Apparently, the radioactive isotopes that had been heating up the Earth's core and mantle for billions of years had run down. Exhausted themselves. Turned off the heat that kept the crust inflated. And so, it collapsed like a pin-pricked balloon.
The privileged wealthy took to the cruise ships. Fully stocked, they set sail, with bands playing, for no destination, nowhere to go, no ports of call to put into. When provisions got low, we faced a choice--a simple one, really—them or us. That's what it always comes down to, in the end.
That's where we are. At the end. The few of us who are left can barely keep the ship functioning. More adrift than being under control, we finally found it. Among the vast emptiness of the never-ending sea, we found it: the last tree.
The vagaries of the Great Collapse somehow kept this low hill above the waterline until the last. There it stood in its final glory. As the hill it stood on slowly sank beneath the waves, we noticed the other ships arriving. Together we watched our world end.
Then we turned on each other.