This is a protective cap that was blown out by the frayed wire below it.
This image depicts an Underground Supply Wire that due to age got brittle and shorted out, blowing a hole in the protective cover and shorting out the panel. To the homeowner it sounded like a cannon shooting off in their basement!
As a result the homeowner had to have the Underground Service and Panel completely replaced. While it is true that wires can and will degrade over time, simply doing a visual check from time-to-time may at least head off an issue before it becomes an emergency.
If you notice any frayed cables or burned wires, please call immediately, we are more than happy to talk you through what needs to be done, whether it’s calling us out, doing a bid, or having the electric company out- we can help you take action.