Earth’s Rising Giants
When we think of mountains, we often imagine towering, immovable structures of rock. It may therefore come as a surprise that mountains are actually dynamic, with their height constantly changing due to the natural forces acting on them. Although these changes take place over many years, the height of our mountains can play an important part on our climate and biodiversity.
Tectonic Activity
Mountain growth is primarily driven by Earth’s tectonic plate activity. In a process called continental collision, two plates collide, generating intense pressure and heat that cause the rocks to soften. This force causes the rocks at the point of contact to fold upwards, forming mountain ranges like the Himalayas. In this region, the Indian plate is pushing into the Eurasian plate at a rate of around 5 cm per year, causing the Himalayas to rise by about 1 cm annually.
Another type of tectonic activity, known as subduction, occurs when one plate slides beneath another. As the denser plate sinks, it begins to melt, triggering volcanic activity that leads to the formation of mountain ranges such as the Andes. In this region, the subduction of the denser Nazca plate beneath the South American plate occurs at a rate of 6 to 10 cm per year, causing the Andes to rise by 5 to 10 millimetres annually.
Volcanic Activity
When pressure builds beneath the Earth’s crust, magma can be forced to the surface in an eruption. Over time, the repeated accumulation of magma from volcanic activity leads to the formation of mountains. Volcanic eruptions typically occur at tectonic boundaries, where such pressure is generated.
In contrast, when tectonic plates are pulled apart in a process known as rifting, magma rises to fill the resulting gap, causing mountains to form along the rift. Mount Etna in Italy is one of the world’s most active volcanoes. Each eruption deposits layers of lava and ash that gradually increases the mountain’s height.
Isostatic Rebound
Isostatic rebound occurs when the Earth’s crust adjusts to changes in weight, much like that of a compressed marshmallow regaining its shape. This effect is typically seen when the mass of mountains is reduced due to erosion or the loss of snow and ice. Isostatic rebound helps counteract the decrease in mountain height by allowing the crust to slowly rise and can take place over many years. For example, the melting of glaciers in mountain ranges like the Alps has caused a slight isostatic rebound, with the land gradually lifting several millimetres per year.
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Gavin Crewe is a regular contributor of informative articles to Oxford Home Schooling.
