The upfolded portion of a fold mountain is called_____?

Analyze the question: It asks for the name of the part of a fold mountain that is folded upward (the crest or arch).

Explain the concept: When compressional forces act on rock layers in the Earth's crust, the layers bend into folds. Each fold has two parts:

• Anticline: the upfold, an arch-shaped crest where the rock layers bend upward.
• Syncline: the downfold, a trough or valley-shaped part where the rock layers bend downward.

Check each option:

• A. Sial: This is the upper layer of the Earth's crust, rich in silica and aluminium. It is not a fold feature.
• B. Anticline: This is the upfolded part of a fold. ✔
• C. Syncline: This is the downfolded part, so it is the opposite of what is asked.
• D. Sill: This is an intrusive igneous feature, a horizontal sheet of magma that hardened between rock layers. It has nothing to do with folding.

Answer: The upfolded portion of a fold mountain is the anticline, which is option B.

Tip: Remember "Anticline = Arch" (goes up) and "Syncline = Sink" (goes down).