That’s incorrect. The Mediterranean, Black, and Caspian Seas are all underlain at least in part by oceanic crust, being the remnants of the former Tethys Ocean that has nearly been obliterated by the collision of Africa and India with Eurasia.
Two. The ocean of water and , the atmosphere - an ocean of air.
Good. I always knew you were with me , Colibri! Let’s say the deep basalt crust sets the standard of the Ocean Floor.
(And I guess there are no other contenders- like, the lake Baikal? or anyone else?
My mistake. I didn’t look beyond the sedimentary deposits. Lots of sediments and salt domes below the seafloor made me think it was still continental crust underneath. It’s oceanic alright.
A continent is a type of island. The largest {2, 4, 5, 6, or 7} islands are usually known as continents, because of the unique properties discussed upthread (tectonic plates, canals, tradition, endemic wombat populations). We’re pretty much defining oceans by continents, anyway: between the Americans and Eurasia / Africa = Atlantic; between the Americas and Eurasia / Australia = Pacific; between Africa, Eurasia, and Australia = Indian; between N. America and N. Eurasia = Arctic; between Antarctica and Africa / S. America / Australia = Southern.
Perhaps an “ocean” has a mid-ocean ridge that drives plates?
^
Looks like all of them have spreading ridges, even the arctic. But basaltic ocean floor is my bet.