First, I love Tumblr and want to keep loving it. And yes, it is immediately terrifying to hear that Yahoo (which, from a lot of our perspectives, is a laughably backwards and culturally irrelevant company) is going to own Tumblr. I sympathize.
Google Earth Engine is a joint project between Google and NASA that allows anyone access to a 30 year time-lapse of the surface of the earth. I made a video about how amazing, terrifying, and important it is.