The word translated as "weak" can also mean "wither" or "dry out." Bashan was known for its good pastureland where people tended sheep and cattle, "Carmel" refers to Mount Carmel, which was known for its tree orchards, and the snow from the mountains in Lebanon kept that place fertile. Since Yahweh dries up all the rivers and causes drought, these fertile places will no longer be fertile. AT: "The fields of Bashan wither, the trees of Mount Carmel die, and the flowers of Lebanon fade" (See: [[rc://en/ta/man/translate/figs-explicit]])
Possible meanings are 1) the earthquake causing the hills to crumble to pieces is spoken of as if the hills were melting or 2) the water from the storms coursing down the hills and causing them to erode is spoken of as if the hills were melting. (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here the word "world" refers to the inhabited places on the earth. The verb for this phrase is understood from the previous phrase. AT: "the world shakes and all the people who live in it collapse" (See: [[rc://en/ta/man/translate/figs-ellipsis]])