- Mount Everest's summit rocks were once seabed sediments with marine fossils present
- The Tethys Ocean covered the region 225 million years ago where the Himalayas now stand
- The Indian Plate drifted north, carrying marine sediments that formed mountain rock layers
Long before Mount Everest became the roof of the world, the rocks that form its summit were lying at the bottom of a sea. Today, the Himalayan peak rises to nearly 8,848 metres above sea level, making it the highest point on Earth.
Evidence of that distant past still exists near the summit. Climbers and geologists have reported marine fossils embedded in the mountain's rock layers at elevations close to 8,000 metres, as per a report in the CSR Journal. These include fossils of trilobites, crinoids and brachiopods. These were organisms that once lived in ocean waters.
When a sea covered the region
Millions of years ago, the region where the Himalayas now stand was covered by the Tethys Ocean.
Around 225 million years ago, the landmass that would later become India lay far to the south of Asia. Between them stretched this wide ocean basin. Over time, sediments gathered along the edges of the Indian landmass. Layers of sand, mud and organic remains slowly built up on the seabed.
Shells and skeletal fragments from marine organisms settled into these deposits. As pressure increased over millions of years, the sediments hardened into rock. The fossils trapped within these layers remained intact even as the Earth's surface began to change.
A drifting continent
The ancient supercontinent Pangaea started breaking apart about 200 million years ago. As the continents separated, the Indian Plate began moving north across the ocean.
By roughly 80 million years ago, India was still thousands of km away from Asia but steadily moving closer. During this time, parts of the ocean floor were pushed beneath the Asian continent in a process known as subduction, similar to what happens today along the Andes Mountains.
Not all the seafloor material disappeared underground. Large amounts of marine sediment were scraped off and compressed along the continental margin, slowly building up layers of rock that would later become part of a mountain system.
When two continents met
Between 50 and 40 million years ago, the Indian Plate finally collided with the Eurasian Plate.
Unlike oceanic crust, continental crust is thick and buoyant. Instead of one plate sliding beneath the other, the collision forced the crust to fold and thicken. Rock layers were pushed upwards, forming the Himalayas.
During this process, the ancient seabed rocks that contained marine fossils were lifted thousands of metres above sea level. Over millions of years, these layers rose to become part of Everest itself.
The Himalayas are not finished growing. The Indian plate continues to move northward, and the collision that built the mountains is still ongoing. Geological measurements show that the range continues to rise by more than a centimetre each year.
At the same time, glaciers, wind and flowing water slowly erode the rock.
