I found a Mud Volcano in California

Ma'am,
I have a query to ask, it is believed that energy cannot be created or destroyed. So, therefore energy should be a constant value. It is also true that the universe is expanding and accelerating its expantion, which needs force. A constant force or energy can only accelerate an object to a specific velocity. But here the universe seems to accelerate to an infinite velocity. The query is that, from where does this energy coming which causes this acceleration, if energy is constant. It seems as if energy is being created in this process. Dark energy should also be a constant force. Also, if the things discovered till now are true, than the acceleration of the universe should stop at some time. 
Kindly revert to my query.
Thank you