The short answer is that cells respond to the chemical environment in which they find themselves. The cells around them, the specific conditions, and feedback from the environment all create specific chemical cues that inform the cells to which genes should be expressed, and in what amounts. Chemicals include hormones, cytokines, general signaling molecules, such as cAMP, etc.
i literally hopped on google for this, lol.
i hope this helps though. :)
Luminosity or magnitude of energy brightness
C. Shield Volcano.. think of Hawaiian volcanoes,they are basaltic eruptions, very effusive and unexplosive and are characterised by slow lava movement and very little tephra from the eruption. The basalt erupted is very hard, dense rock and so can be built up easily.