3. A minimal volume of 5 ml of a pooled BAL sample is needed for BAL cellular analysis. The optimal volume is 10 to 20 ml. It is acceptable to pool all aliquots of the retrieved BAL ï¬uid for routine analyses (including the ï¬rst retrieved aliquot). 4. BAL cell differential counts with greater than 15% lym-
So when a continent meets a continent, no subduction occurs (instead, the plates collide and thicken). True subduction happens only to oceanic lithosphere. When oceanic lithosphere meets continental lithosphere, the continent always stays on top while the oceanic plate subducts.
At converging plate boundaries, two situations are possible. First, both volcanoes and earthquakes form where one plate sinks under the other. This process, called subduction, takes place because one plate is denser than the other. The denser plate, which invariably has oceanic crust on its top, does the sinking. Second, only earthquakes occur when two plates collide (obduct), building a mountain range.