What determines the level of Earth’s crust? Climate change may change it all

The land is not level and you know that. Some parts of the world may look flat (no mountains) and yet they are higher than everything that surrounds them. What determines the level of the land? Scientists at the Victoria University of Wellington decided to figure it out and found a deep anchor beneath the continents.

If it loses its thick ice layer, Antarctica may just bounce up becoming the highest continent in the world. Image credit: Gary Bembridge via Wikimedia (CC BY 2.0)

Earth is changing. Due to rising temperatures ice is melting more and more rapidly. As ice sheets are disappearing, sea levels are bound to rise. This will change the land levels in some places, but it is difficult to calculate how. For the longest time scientists assumed that Earth’s crust determines the level – it is floating on the underlying mantle like a rocky iceberg. Scientists assumed that the thicker the crust, the higher it rises above the level. However, now they are not so sure about that picture, because, as this new study shows, there is little correlation between the average elevations of the continents and the thickness of the crust in that area.

For example, Australia has a relatively thick crust, but has a lower level. At the same time New Zealand is pretty much the same level, even though its crust is not that thick. Scientists say that it doesn’t depend solely on the crust, but also on what’s beneath it.

So what is going on? Well, the crust is floating on the mantle like an iceberg in the sea – that’s what we call tectonic plates. However, crust is not the only part of the tectonic plates. Scientists found that tectonic plates might have roots, which act like anchors keeping the level lower despite the lower density crust wanting to rise a little higher.

Crust is always getting eroded by the water. Everywhere, except Antarctica, which is too cold for any kind of rivers. And this is why it is important to understand these processes now in the midst of the accelerating climate change. Associate Professor Simon Lamb, lead author of the study, said: “Today, the weight of the vast East Antarctic ice sheet is pushing down the underlying bedrock. However, if all the ice melts—perhaps due to uncontrolled global warming—the surface of East Antarctica will bounce back over the following 10,000 years or so to form the highest continent of all, about 1km on average above sea level.” This is one of the many reasons why geologists will be watching climate change very carefully.

It is crazy to think that we are living on giant sheets of rock floating on unbelievably hot magma. However, this is how our Earth is constructed. Even more crazy is the fact that we barely know what is inside of our planet. Hopefully, researches like this will help us uncover Earth’s secrets.


Source: Victoria University of Wellington

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