I’ve seen many youtubes - History Channel - showing very unusual structures, very well built, under water. The ocean must have been quite a bit lower quite a few thousands of years ago. Tons of other things. History is very different from the generally accepted timeline.
Yup. The ice age. When the ice age ended, the water level rose on the coasts a lot. 50 feet? 100 feet? 150 feet?
People live on the coasts now. All the ice age coasts are now underwater. There is likely a lot more undiscovered stuff underwater.
Not really. But the land does move up and down, all the time.
Common estimates based on the amount of water tied up in continental ice sheets during the last ice age put the Sea Level during the Ice Age at some 300 ft. lower.
If you think about human settlement patterns, that would put the largest trade hubs and cities of the time out on the Continental Shelf, provided such existed.
The climate change and rise in sea level (what the AGW people are so terrified of now, even if it isn't happening) would be rough on a civilization, but not insurmountable if the civilization recognized what was happening and moved inland.
Of course, conflict over real estate would ensue, just as it has at any time one group of people invaded another, and much as it might today if, say, the populations of the East and West Coast cities were to attempt to move inland to elevations higher by 300 ft. or more. That would be the biggest impediment to the survival of a culture based on oceanfront property. Loss of coastal plains croplands would likely have an adverse effect on population as well.
15,000 years ago the sea level was 300-400 feet lower than today. The area of the Persian Gulf would have been dry land.
Prior to the Great Melt (lasting from 16000 - 8000 BC), sea levels were 400-700 feet lower.