Must have been catastrophic.
Can any one say the lost continent of Atlantis?
‘beyond the pillars of Heracles(the Straits of Gibraltar),’ there lay an island which was larger than Libya and Asia(Minor)together; and it was possible for the travelers of that time to cross from it to the other islands, and from the islands to the whole of the continent over against them which encompasses that veritable ocean.....
.....But at a later time there occurred portentous earthquakes and floods, and one grievous day and night befell them, when the whole body of your warriors was swallowed up by the earth, and the island of Atlantis in like manner was swallowed up by the sea and vanished; wherefore also the ocean at that spot has now become impassable and unsearchable, being blocked up by the shoal mud which the island created as it settled down.”
According to Plato Atlantis disappeared 11,700 years ago. According to a new study Europe endured a very sudden and catastrophic climatic change around 12,000 ago. Coincidence?