Volcanic eruptions occur at tectonic plate boundaries where molten rock, or magma, is forced to the surface of the Earth. This usually happens at the boundaries of the Earth`s crust where the plates are colliding or separating.

Option 1: Baltic Sea - This sea is located in Northern Europe and does not sit along any tectonic plate boundaries. This means there is no volcanic activity and thus, no volcanic eruptions occur here, making it the correct answer.

Option 2: Black Sea - Although the Black Sea is not known for volcanic activity, it is surrounded by regions that have experienced historic seismic activity, including volcanic eruptions.

Option 3: Caribbean Sea - This area is known for its active seismic and volcanic activity because it lies on the edge of the Caribbean Plate.

Option 4: Caspian Sea - While the Caspian Sea itself does not have volcanic activities, it is a part of a larger region that includes the Caucasus Mountains to the west, which are situated on an active tectonic boundary, hence might have had some volcanic eruptions in the geological past.

So, the Baltic Sea is the best answer as there`s no volcanic activity there.