Mount Everest, the world’s highest peak, reveals a geological history of ancient oceans and continental collisions. Its unique geology tells a story vastly different from its current towering elevation.
The Summit’s Rock Formation
The summit of Mount Everest is primarily composed of limestone. This Ordovician-age limestone, formed 450 to 520 million years ago, is known as the Qomolangma Formation (historically, Everest Limestone).
The presence of limestone indicates a marine origin, as this rock typically forms in shallow, warm ocean environments. Fossilized remains of ancient marine organisms have been discovered within this summit limestone, providing direct evidence of its ancient seabed origin. These include:
- Crinoids
- Trilobites
- Brachiopods
- Ostracods
The Qomolangma Formation has experienced some deformation and low-grade metamorphism, with temperatures increasing towards its base.
Geological Journey to the Top
Marine limestone at Everest’s summit is explained by the geological processes that created the Himalayas. This mountain range, including Mount Everest, formed as a direct result of the collision between the Indian and Eurasian tectonic plates. This collision began approximately 40 to 50 million years ago.
Before this collision, a vast body of water known as the Tethys Ocean separated the Indian landmass from Eurasia. Sediments, including the future summit limestone, accumulated on the floor of this ancient ocean. As the Indian plate moved northward and collided with the Eurasian plate, the Tethys Ocean gradually closed.
The continental plates, having similar densities, could not easily subduct one beneath the other. Instead, the immense pressure caused the oceanic sediments and the crust to compress, fold, and thrust skyward. This uplift, driven by the Indian plate’s northward movement at a rate of 5 to 10 millimeters per year, continues to shape the Himalayas today.
Everest’s Diverse Rock Layers
While the summit is known for its marine limestone, Mount Everest is structurally complex and composed of several distinct rock formations. From its base to the summit, these include the Rongbuk Formation, the North Col Formation, and the Qomolangma Formation. Each formation represents different geological periods and conditions.
The base of Mount Everest consists of the Rongbuk Formation, which comprises older metamorphic rocks such as schist and gneiss, along with granite intrusions.
Above this lies the North Col Formation, which includes the recognizable “Yellow Band.” This band is a prominent yellow-brown layer of metamorphosed sedimentary rocks like marble, phyllite, and semischist, visible just below the summit pyramid.
The Yellow Band also contains some fragmented crinoid fossils, though they are more altered due to higher temperatures and pressures compared to those at the summit.
The Qomolangma Formation then forms the uppermost section of the peak, extending from approximately 8,600 meters to the very top. This is the fossil-bearing limestone layer that caps the world’s highest mountain. These major rock units are separated by low-angle faults or detachments, illustrating the significant tectonic forces involved in their stacking and uplift.