A new thermal area has popped up in Yellowstone National Park, in yet another sign of the ever-changing magma activity beneath the surface.

Satellite images have revealed an expanse of about eight acres – or the equivalent of four soccer fields – where the ground is warmer than its surroundings, causing the trees and vegetation in that patch to die off.

While scientists have only just confirmed its existence, the United State Geological Survey (USGS) estimates it’s been forming over the last 20 or so years.

A look through the imagery going back to the 1990s confirmed what they suspected – a growing bright patch in the middle of the forest. by 2006, the beginnings of a ‘tree kill zone’ become to be apparent in the images. Now, the change is unmistakable

The massive new thermal area is marked by a 'tree kill zone,' seen above, where trees and other vegetation are dying out

In a new post for the USGS weekly Caldera Chronicles, scientists have revealed the existence of a new thermal area near Tern Lake.

These areas are home to one or more thermal features, such as hot springs or geysers, of which there are more than 10,000 scattered across the park.

Thermal features are grouped into about 120 distinct thermal areas, USGS explains.

Deep in the back country between the already established Tern Lake Therma Area and West Tern Lake, scientists have noticed a growing patch where trees seem unable to survive in the last few years.

A look through the imagery going back to the 1990s confirmed what they suspected – a growing bright patch in the middle of the forest, signaling warmth beneath the surface.

On the right, dark pixels represent frozen lakes during wintertime. West Tern Lake may be thawing as a result of thermal waters from nearby hot springs. The bright (warm) pixels between West Tern Lake and the Tern Lake thermal area has emerged over the last 20 years

Satellite images have revealed an expanse of about eight acres – or the equivalent of four soccer fields – where the ground is warmer than its surroundings, causing the trees and vegetation in that patch to die off

‘Analysis of a Landsat-8 nighttime thermal infrared image acquired in April 2017 revealed an unexpected warm area between West Tern Lake and the previously mapped Tern Lake thermal area,’ USGS says.

In 1994, the space between Tern Lake Thermal Area and West Tern Lake was covered in trees and vegetation

‘This mysterious patch of bright pixels in the thermal infrared image did not match any previously mapped thermal areas.’

In 1994, the space between Tern Lake Thermal Area and West Tern Lake was covered in trees and vegetation.

But, by 2006, the beginnings of a ‘tree kill zone’ become to be apparent in the images.

Now, the change is unmistakable.

‘The most recent image of the Tern Lake region, from 2017, reveals a large area of dead trees and bright soil, rather like a thermal area,’ USGS says.

‘From all these satellite and aerial images, we conclude that a new thermal area has emerged in the past 20 years!’ the team added.

Its appearance is no cause for concern. According to the experts, the activity goes in line with what’s expected for the Yellowstone area.

Thermal areas are marked by a 'tree kill zone,' where vegetation is unable to thrive. West Thumb, for example, can be seen above in Yellowstone National Park