Why methane and silicon dioxide have different melting points?

Methane, consists of discrete molecules with a formula CH4. Silicon dioxide, SiO2, is a covalent macro-molecule consisting of a lattice of covalently bonded Si and oxygen atoms (each silicon is attached to four oxygen atoms, each oxygen is attached to two silicon atoms.

Solid methane is held together by intermolecular forces- London dispersion forces, which are weak., so relatively little thermal energy is required to break up the solid (-182 0C) Breaking the silicon dioxide lattice requires the breaking of strong covalent bonds- which requires much more energy- so it melts at a much higher temperature, 1600 0C