How do observations of earthquake and volcanic activity support the theory of plate tectonics?
you for taking the time to ^_^

They provide evidence that movements of the crust are a result of slow moving currents in the mantle. Since earthquakes and volcanic eruptions are usually a result of stick-slip movements between 2 more plates and it is tension changes that are responsible for this sudden movement, the plates must be moving overtime or this tension would remain fairly constant.

Water flows along the east coast and across the western tropical pacific towards south america, while they both are directed towards that way,  el niño does not directly affect the southern flow of water along the coast.