Geology of Mount Everest
The three formations, or units, which make up the geology of Mount Everest are divided into sections. Geologists have named these, from the bottom to the summit respectively, the Rongbuk Formation, the North Col Formation and the Qomolangma Formation. These sections, or units, are divided by a low-angle fault, or a ‘detachment’, each one being forced over the next to form a, sort of, zigzag pattern.
The Qomolangma Formation, otherwise known as the ‘Jolmo Lungama Formation’, consists of layers of Ordovician limestone and recrystallized dolomite, along with siltstone and laminae, together forming colours ranging from white to dark gray. Starting at 8,600 meters above sea level (above Yellow Band), the Qomolangma Formation ends at the summit. Tests of the limestone found here have been conducted to reveal small remains of ostracods, trilobites and crinoids. Gansser was one of the first people to report such findings.
Lots of samples were taken, but some had been recrystallized, thus no conclusive results were found in regards to the contents. The bottom of the summit pyramid and the ‘Third Step’ is made up of a bed, 60 meters in depth, which sticks out from about 70 meters beneath the top of Mount Everest. This bed contains trapped sediments, which are sealed in by the production of biofilms from micro-organisms, such as cyanobacteria, usually in marine waters that are quite shallow. This section is scattered with a number of high angle faults, which finish at the Qomolangma Detachment. This causes a separation from the ‘Yellow band’.
The middle part of Mount Everest is known as the North Col Formation, 7,000 to 8,600 meters. This section, itself, can be divided into different parts, the top 400 meters, named the ‘Yellow Band’, is formed from linked beds of a brown, Middle Cambrian, marble (diopside-epidote-bearing), muscovite-biotite phyllite (which contain silicate minerals) and semischist (a partly metamorphosed, layered sedimentary rock). By analysing some of the marble taken from around 8,300 meters, it has been discovered to contain up to 5% crinoid ossicles (marine organisms which have a skeleton, formed from calcareous plates), which have been recrystallized. The top five meters, just before the Qomolangma Detachment, is a badly deformed area and is separated from the Qomolangma Formation by a fault breccia, which is between 5 and 40 centimeters thick.
The rest of the North Col Formation is formed from layers of minor marble, schist and phyllite. From 7,600 to 8,200 meters, schist (biotite-sericite-quartz) can be found in small amounts, along with chlorite-biotite phyllite and biotite-quartz phyllite. The bottom, consisting of the last 600 meters, is formed by the combination of, biotite-quartz schist, biotite-calcite-quartz schist and epidote-quartz schist, occasionally separated by a thin quartzose marble layer. The formation of these rocks is thought to have occurred due to the metamorphism of deep sea flysch (Middle Cambrian) and made up of sandy limestone, calcareous sandstone and mudstone, among others. The ‘Lhotse detachment’ (a regional thrust fault) lies at the bottom of the North Col Formation, dividing it from the Rongbuk Formation.
The lower section of Mount Everest is known as the ‘Rongbuk Formation’ and makes up the first 7,000 meters. This region of Everest is formed from sillminite-K-feldspar grade schist and a banded metamorphic rock called gneiss, which has a similar composition to granite. Also a number of dikes of leucogranite and sills, which are horizontal sheets of igneous rock stuck between older rock beds.
It is thought that the summit of Mount Everest started at the bottom of the ancient Tethys Sea, the motion of the Indian subcontinental plate and the urasian continental plate colliding, about 30 – 50 million years ago, caused the mountain to rise up and become the highest mountain on the Earth.
Geology of Mount Everest (C) Google Earth Annotation by Miles Traer