I have a continent and I want the sea level to rise temporarily, for several hundred years. The area that needs to be covered by water is about 3 million square kilometers.
I was thinking about a big earthquake, triggering sinking of a tectonic plate. The side of the plate near the sea sinks and the other side stays mostly unchanged. This will be experienced as leaning of the ground. The molten rocks that were below the plate must go somewhere so that will probably trigger volcano eruptions and mountain formations.
The sea must cover whole mountains near the sea (hundreds of meters). After several hundred years the process has to reverse (the sea level has to drop).
Is anything like that possible in such a short time range? Are there any alternative explanations for such a phenomenon?