Which Came First?

From USGS Volcanoes:

Would you like to try this #volcanopopquiz? Here it is: which came first, the lava flow or the tuff ring? Like a geologist in the field, make an observation about the field relationships between the two different volcanic deposits/landforms. #MonoCraters Photo by M. Marcaida. Check out: http://volcanoes.usgs.gov/volcanoes/mono_inyo_craters/ #californiavolcanoes#californiavolcanoobservatory #calvo #usgs #volcanoes