Was doing a search for Detroit on Google Realtime and noticed that the timeline can be scrolled. This means you can see what the topic was that spiked activity at that time. Detroit is a rather common word and has frequent activity posted. It looks like there were two small spikes after 6 PM and another at what looks like 11 PM.
See image below. You can try the Detroit search here.
*Perhaps I should have done a screenshot of one of the spiking periods for analysis.