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.
When it reaches the surface, a volcano is formed. The magma flows out as lava, sometimes explosively. The majority of the world's volcanoes are associated with subduction zones. Since subduction zones represent plate margins, volcanoes tent to occur in lines, like the Cascade Range volcanoes or those on the Aleutian Peninsula. Once in a great while, a new volcano will form. This usually happens when an active underwater volcano produces enough lava to break the surface, such as Surtsey in Iceland in 1963.