Yahoo has officially announced that it will acquire Tumblr in a $1.1 billion cash deal expected to close in the second half of the year, and will keep Tumblr’s David Karp on as CEO. “Per the agreement and our promise not to screw it up,” Yahoo says in its press release, “Tumblr will be independently operated as a separate business.” In one of its first acts of business, Yahoo has moved its official blog to yahoo.tumblr.com. “Tumblr is redefining creative expression online,” Yahoo CEO Marissa Mayer said in the announcement. “On many levels, Tumblr and Yahoo couldn’t be more different, but, at the same time, they couldn’t be more complimentary. Yahoo is the internet’s original media network. Tumblr is the internet’s fastest-growing media frenzy.” In a blog post discussing the change, Mayer insisted that Yahoo won’t “screw up” Tumblr, and that it will operate independently.