The 1888 LDS large-print edition accidentally set the present-tense ascendeth as the past-tense ascended, probably because of the preceding past-tense was. Nonetheless, the following presenttense hath (“and hath no end”) shows that this eternal flaming fire should be referred to in the present tense. Similar passages also use the present-tense ascendeth:
Also see the discussion regarding separateth under 1 Nephi 15:28.
Summary: Maintain the present-tense ascendeth in 1 Nephi 15:30.