Consider the following geological structures and tectonic settings: 1. Rift valleys are formed by tensional forces creating fault-bounded grabens where central blocks drop relative to flanking horsts. 2. Fold mountains are primarily created through compressional forces at convergent plate boundaries where crustal strata buckle and uplift. 3. Shield volcanoes are constructed from explosive viscous felsic lava flows that create steep-sided conical peaks. Which of the statements given above are correct?

💡 Solution & Explanation

Statements one and two are correct because tensional tectonic forces cause normal faulting that produces grabens and horsts, while convergent plate boundaries generate compressional folding characteristic of major mountain ranges. Statement three is incorrect because shield volcanoes are formed by fluid, low-viscosity basaltic lava flows that spread widely to form broad, gently sloping domes, whereas steep-sided cones are built by viscous andesitic or rhyolitic lavas. Basaltic volcanism characterizes oceanic hotspots and divergent boundaries.