Which is the oldest mountain of South America continent ?
Pacaraima
The Pacaraima range is the oldest of those named — option 1.
Why. The Pacaraima mountains lie on the borders of Venezuela, Brazil and Guyana and form part of the Guiana Shield — a block of Precambrian rock more than 1,700 million years old, among the most ancient exposed crust on Earth. Its rocks are the eroded roots of mountains far older than any of the present ranges, and the tabletop mountains, or tepuis, that rise from it — Mount Roraima chief among them — are the remnants of a once-continuous sandstone plateau.
| Range | Type and age |
|---|---|
| Pacaraima | Guiana Shield — Precambrian, over 1,700 million years; the oldest |
| Tumuc-Humac | Also on the Guiana Shield, on the Brazil-Suriname border, and likewise ancient, but the range named in the standard answer for this question is Pacaraima |
| Andes | Young fold mountains, raised from the Cretaceous onward and still rising; the youngest of the group |
| “Brazil Mountain” | Not a recognised range; the Brazilian Highlands are a shield plateau, not a mountain chain of this name |
The general principle. Mountains are classified by origin, and origin fixes age :
| Type | Character | Example |
|---|---|---|
| Residual or relict | Ancient, heavily eroded, low and rounded; the worn stumps of former ranges | Pacaraima, Aravalli, Appalachians, Urals |
| Fold | Young, high, sharp-peaked, seismically active | Andes, Himalaya, Alps, Rockies |
| Block | Raised between faults, with steep scarps | Sierra Nevada, Vosges, Black Forest |
| Volcanic | Built by eruption | Fujiyama, Kilimanjaro |
The test to apply : a high, jagged, earthquake-prone range is young; a low, rounded, stable one is old. The Andes are the obvious high range of South America, and that very fact makes them the youngest, not the oldest — which is the trap in option 3.
Hence, the answer is Pacaraima.
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