Please provide the specific mid-oceanic ridge you are referring to. There are many mid-oceanic ridges around the world, and the geologic events that occur most often vary slightly depending on the ridge's specific location and characteristics.

For example:

* Mid-Atlantic Ridge: This ridge is known for its slow spreading rate, resulting in a relatively smoother topography with fewer volcanic eruptions.

* East Pacific Rise: This ridge has a faster spreading rate, leading to more frequent volcanic eruptions and a steeper, more rugged terrain.

Once you specify the mid-oceanic ridge you're interested in, I can give you a more accurate answer about the geologic events that occur most often there.