Why does it mention north and right?
Radak citing Ibn Ezra: It mentions the corners of the world. Verse 12 mentioned Shamayim and Aretz, the extremes above and below. Now it mentions north and right (i.e. south), Tavor (west) and Chermon (east). These are the six Taba'os (corners) mentioned in Sefer Yetzirah.
Radak: "Tevel u'Mlo'ah" (verse 12) is east to west along the equator. North and right (south) are not totally settled). Much of the north is desolate due to the great cold there. Much of the south is desolate due to the great heat there 1 .
Malbim: It explains how Hashem established Tevel. The north and south, near the poles, is not proper for settlement due to the great cold there.
Perhaps Radak (who lived in France) knew that the Sahara desert is desolate, and assumed that the world keeps getting hotter to the south. (PF)
Why does it say "Atah Verasam"?
Radak: All agree that You created the desolate and inhabited places.
Malbim: Initially, Hashem created the world from void; it was "Sohu va'Vohu" (Bereishis 1:2), not proper to be settled. Afterwards He formed it to be proper for settlement - "Yotzer ha'Aretz v'Asah Hu Chonenah Lo Sohu Vera'ah" (Yeshayah 45:18). He did not form the north and south poles; he left them desolate, like they were created.
Why does it mention Tavor and Chermon?
Radak citing Ibn Ezra: Refer to 89:13:1:1.
Radak: They are great mountains, among the awesome creations in the land - "Ki ch'Savor be'Harim" (Yirmeyah 46:18) - it is known for its length and height. "L'Chermon
Why does it say "b'Shimcha Yeranenu"?
Radak: It is as if they tell, sing and testify that You create them. One who sees them, he praises the One who forms them; it is as if [the mountains] sing.
