What Are the Highest Mountain Ranges Made Of? Metamorphic Cores Uplifted by Tectonics

The world's highest ranges (Himalayas, Andes, Karakoram, Hindu Kush) are dominated by high-grade metamorphic rocks formed deep in the crust.

Rock Sequence (Bottom to Top)

1. Basement gneisses & granulites: Ancient continental crust (1–2+ Ga), recrystallized at 30+ km depth.
2. Metasedimentary sequences: Former marine sediments (shale, sandstone, limestone) metamorphosed to schist, quartzite, marble.
3. Granitic intrusions: Leucogranites from crustal melting (Miocene in Himalayas).
4. Overlying sedimentary cover: Unmetamorphosed Paleozoic–Mesozoic limestones, shales (often thrust over core).

Key Rock Types

• Gneiss: Banded, high-grade metamorphic (feldspar, quartz, mica).
• Schist: Foliated, mica-rich (muscovite, biotite).
• Quartzite: Metamorphosed sandstone — extremely hard, forms cliffs.
• Marble: Metamorphosed limestone — karst features.
• Eclogite: Ultra-high pressure (subducted crust) — diamonds, coesite.

Tectonic Process

Continental collision (India-Asia, Nazca-South America) → crustal thickening → burial → metamorphism → exhumation via thrust faulting & erosion. Peaks expose deepest rocks.

Why Not Igneous/Volcanic?

Volcanic arcs (Andes western flank, Cascades) are lower. Highest peaks are collisional, not volcanic (except isolated stratovolcanoes like Kilimanjaro).