The spheres are placed together by magic, no impact energy. Fine.
Now you have a rock, with a rock’s tensile and compressive strength, looming fifteen hundred miles over the Pacific. Mountain sized chunks will break off instantly, and freefall thousands of miles, striking the atmosphere at extreme velocities, and then striking the sea, or the coast of some continent. It will happen often, and fairly rapidly, and the heat generated by the impacts will pretty much vaporize the portion of the sea on that side of the Earth, and then start vaporizing the Crust, and the Moon Rock as well. All this heat will fairly rapidly melt the crust, and release the internal heat of the mantle, and the now very turbulent core.
It won’t be gradual, it will be catastrophic. No single event in Earth’s history released this much energy since the Moon was originally formed. No life will survive, not even single celled life. The atmosphere of earth will be plasma for centuries. The irregular, and off center rotation alone will generate enough energy to liquefy the entire mantle. We will have to await the New Cambrian era to see life again.
Quibble how you will, the amount of energy released will be the same as dropping the Moon on the Earth from a distance equal to its radius. When we talk of slower, we are only talking about the total length of time to reach equilibrium. The immediate event will be anything but gradual. The famous dinosaur comet is a trivial little spark in comparison. In fact, every single known impact event put together are trivial in comparison.
I too urge you to reconsider this dangerous plan.
Tris