1. Why Rocks Near Everest's Summit Contain Fragments of Sea Life
The rocks near the summit of Mount Everest are limestone that accumulated in a shallow tropical sea about 450 million years ago (some sources say 470 million years ago), and they contain fragments of the skeletons of sea creatures [2]. This location is one of the "First 100 Geological Heritage Sites" selected by the International Union of Geological Sciences (IUGS) [2]. It is important to note that these two dates are different. The stone was formed about 450 million years ago, but it began to be lifted up about 50 million years ago, as we will see later. The stone slept on the sea floor for a long time, and it became a mountain much later. So, what force carried the sea stone to a height of more than 8,000 m (about 5 miles)?
2. How the Collision of Two Continents Pushed Sea Stone Upward
The answer is the movement of the plates that cover the Earth's surface. The plate carrying the Indian subcontinent moved north and collided with the Eurasian plate. The crust at the collision site was pushed and lifted, forming the Himalayas and the Tibetan Plateau [3]. The start of the collision varies by source, ranging from about 40 million to 55 million years ago [3]. This article rounds it to "about 50 million years ago." Mountains pushed up by collision are also relevant to Japan. The Pacific Plate and the Philippine Sea Plate push against the Japanese archipelago from the Pacific side, subducting under the islands, creating strong compressive forces [1]. However, no official source has been found that attributes the abundance of mountains in Japan to a single reason. The pushing force is just one clue, so we will leave it at that.
3. How Volcanoes Build Mountains From Ash and Lava
There is another way mountains are made. It is the path where volcanic ash and lava from eruptions accumulate repeatedly in the same place to form a mountain. Mount Fuji is a representative example; it is a stratovolcano with an elevation of 3,776 m (about 2.3 miles) [7]. The current Mount Fuji has a new mountain sitting on top of an old one. The new Fuji volcano, which began activity about 11,000 years ago, formed on top of older volcanoes called Komitake and Old Fuji [7]. The start of new Fuji varies by source, ranging from about 11,000 to 17,000 years ago. Volcanoes are unevenly distributed around the world. About two-thirds of the world's volcanoes are in the Circum-Pacific volcanic belt, and many are thought to have formed where plates subduct [9]. Both mountains pushed up by collision and volcanoes built by accumulation are related to plate movement. However, the direction of the force forming the mountains is very different between these two paths.
4. Why Mount Everest Is Still Rising Each Year
Mountains do not stop after they are formed. Recent GPS observations report that Mount Everest is rising by about 2 mm per year [4]. This exceeds the previous prediction of about 1 mm per year [5]. If 2 mm continues for 10,000 years, it becomes 20 m (about 65 feet). Even changes invisible in one year can become great heights over long periods. It has been suggested that river activity is related to this rise. About 89,000 years ago, a "river capture" occurred where the Arun River was taken by the Kosi River, and the valley was deeply eroded. It is estimated that the mountain, lightened by erosion, was pushed up as if floating (isostatic rebound), potentially raising Everest and others by 15 to 50 m (about 50 to 165 feet) [5]. This is a research estimate, and the description of which river captured the other varies by source. It is a story that stays at "it is possible."
5. How Rising Land and Erosion Balance to Set Mountain Height
What stops a mountain from getting higher is the force of erosion. Rain, rivers, glaciers, and landslides erode mountains. One way to think about mountain height is the balance between uplift and erosion [8]. In places where uplift is fast, the average height tends to balance out at a higher level. A study in the Kurobe area of the Northern Japan Alps shows this relationship. According to a 2026 announcement by Kyoto University, granite analysis showed that uplift and erosion occurred at one of the world's highest speeds over the past 800,000 years. The speed reaches about 1 cm per year [6]. 1 cm is 1 m (about 3 feet) in 100 years. This 1 cm per year is the speed of uplift and erosion, not the current rise measured by GPS. Also, no fault lifting the Northern Japan Alps has been found; numerical analysis suggests that deformation concentrated in the crust heated by volcanic activity is the background [6].
6. How Pushing, Volcanoes, and Erosion Shaped Japan's Mountains
Japan's mountains mix the three paths in this article: the force of plates pushing [1], volcanoes accumulating from eruptions [7], and mountains being eroded while rising [6]. The Southern Japan Alps have also been uplifting since about 1 million years ago, with rates said to be about 3 to 4 mm per year, and they are said to be the fastest in Japan [10]. However, values differ depending on the measurement method and period, and GPS results are lower. The mechanism of uplift in the Northern Japan Alps is also debated among experts. What we notice here is that the view of "mountains are static things" is the exception when viewed over long periods. Mountains are being pushed, accumulated, and eroded, slowly changing shape even now.
7. How to Tell Which Process Made a Mountain Near You
Let's look at a mountain or hill near your home with two questions: "Is it a shape pushed and lifted up?" and "Is it a shape accumulated by a volcano?" A cone shape like Mount Fuji suggests a volcano, while a chain of mountain ranges is one clue that they may be mountains pushed by plates. If you can go to a riverbed, look at a stone with an adult. That stone may have been eroded and carried from upstream mountains or land. It is a small sample of how mountains are eroded. Please do not approach rivers during floods or near the water's edge, as it is dangerous. Maps and topographical data are published by the Geospatial Information Authority of Japan. Investigating "which path made this mountain?" yourself is also a fun way to learn.