What is the silica content of magma that has a low viscosity? ?

The viscosity of magma is directly related to the silica content. That being said, the viscosity of magma is higher when the silica content is also high and it is a low viscosity magma when the silica content is also low. The silica content of low viscosity magma is approximately 45 - 55 wt%. 

For the answer to the question above, the answer is 
low silica content 
(basaltic magma)
or should I say the answer is Magma with high viscosity
I hope my answer helped you. Feel free to ask more questions. Have a nice day!

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -