In the world my friend and I are making, the dark lord makes one of the planets uninhabitable by causing a moon, about the size of our own, to fall on it. About 7000 years later, it is unnaturally cooled down via deus-ex-machina. What would be the impacts of this event on the planet itself? The planet is about the size of Earth.
I am asking what effects the impact would have on the natural terrain of an Earth-like planet and how that would look when the land in and outside of the crater is cooled down and oceans re-form 7000 years later, unnaturally. Note: I am asking about how it affects the planet, I would understand it more easily by considering how the planet would look because of the moon-fall after 7000 years when the oceans re-form. Don't worry about how the oceans re-form, its deus-ex-machina and that part doesn't matter. I am asking specifically about the terrain and what it looks like.
I recently found a similar question here, but just like the question that this question I found references, it's answers don't help me and aren't specifically the same question since we are really focusing on opposite sides of the planet. He is focusing on the area opposite the area of impact, and on a much larger time-scale, while I am focusing on the area of impact.
I just decided that my world is in the process of becoming a Q-ball world before the moon-fall. Ie. it is tectonically inactive, though it hasn't entirely lost its magnetic field, erosion hasn't washed away it's mountains yet either. I don't know how this will work, but I am wanting to make it really cold deep-down before the moon-fall (though there is an iron core and it does hold a relatively high density). I don't know if this detail matters.