It started around 175 million years ago when the supercontinent Pangaea began to break apart, causing a vast increase in seismic and volcanic activity. For our ancient ancestors the floor actually WAS lava. This frightening epoch in human history was later remembered by the grateful survivors in an annual reenactment and day of mourning for lost loved ones. This is why it is still known throughout the modern world.
welcome to 2016, where it's too soon to make jokes about any tragedy ever
'Murica!