This is because snow and ice "exist relatively close to their melting point and frequently change phase from solid to liquid and back again."
(This; is; because snow and ice "exist relatively close to their melting point and frequently change phase from solid to liquid and back again) (snow and ice; exist relatively close; )
This snow and ice
is exist relatively close
because snow and ice "exist relatively close to their melting point and frequently change phase from solid to liquid and back again