ונתת את הברכה על הר גריזים ואת הקללה על הר עיבל ... (יא-כט)
The two mountains, Har Gerizim and Har Eival, are both located in the mountain range of Shevet Ephraim, and the contrast in their appearances can be clearly seen. Mount Gerizim, located to the south of the valley of Shechem, is verdant, lush, with gardens covering the terraces on its slope. Mount Eival, on the north side, is steep, barren and desolate. Mount Eival is approximately 2,900 feet high, a few hundred feet taller than Mount Gerizim, which rises to about 2,700 feet.
Accordingly, writes R’ Shamshon Raphael Hirsch zt”l, these two mountains, standing side by side, present a striking visualization of blessing and curse. Both of them rise from the same soil; both are watered by the same rain and dew. The same air passes over both of them; the same pollen blows over both of them. Yet, Har Eival remains starkly barren, while Har Gerizim is covered with lush vegetation to its very top. There is clearly a stark contrast between the two mountains. In the same way "ברכה וקללה" - blessing and curse - are not dependent on external circumstances, but rather on a person’s inner receptivity to one or the other - on our attitude towards that which brings about blessing.
When Bnei Yisroel crossed the Yarden (Jordan River) and took those first steps on the soil of a Holy Land that sanctified them, the sight of these two mountains taught them that they, by themselves, by their OWN moral conduct, will decide whether they were headed for Mount Gerizim or Mount Eival - for blessing or for curse.
Avraham Avinu, too, came first to these mountains when he entered the Land of Canaan, and built the first mizbeach (altar) to Hashem, when He appeared to him at Elon Moreh. The word "מורה" translates as “teaching” because the lesson that Avraham was taught when he beheld the two mountains is that it is up to him to choose which way his life will go - closer to the Creator of the World and His Torah - blessing - or chalilah, the opposite - towards curse.