>Is this an ancient Volcanic Crater?
Nope. This was caused awhile back when the Earth experienced an incredible Force, reshaping entire continents, that needed to redistribute millions of Amps worth of Electrical charges that clings to the surface of our planet. Electricity acts differently as it travels through different types of matter. The salt water oceans are conductive, but the land acts more like a resistor. Charge from the Pacific tried to balance with that of the Atlantic, but our continent got in the way, creating the unique geological features which tend to baffle the "scientists" who take the mainstream uniformitarian approach, which require several thousand years of "mysterious" process.