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.
Why volcanoes occur near subduction zones: compression heats the rocks; the descending slab begins to melt; hot rocks is uplifted by mountain-building events; tension opens cracks so material from the core can rise. The San Andreas Fault is: a transform fault; a subduction zone; a rift valley; a zone of collision between two continents