"Satellite images of western Shiyan between 2010 (L) and 2012 (R) show that several peaks have been flattened."
"China's campaign to bulldoze mountains to create land to build on could cause extensive environmental problems, scientists say.
They say that this activity is happening on an unprecedented scale.
They report their concerns in the journal Nature.
Prof Peiyue Li, from Chang'an University's School of Environmental Science and Engineering, said:
"Because there have been no land creation projects like this before in the world, there are no guidelines."
About one-fifth of the country's population lives in mountainous areas.
Around the country, in cities such as Chongqing, Shiyan, Yichang, Lanzhou and Yan'an, dozens of hilltops have been levelled.
The soil and rock is then used to fill in valleys, and overall this has so far created hundreds of square kilometres of flat terrain.
Prof Li said: "Mountainous cities such as Yan'an are mostly located in relatively flat valleys. "The valleys are narrow and limit the development of the cities - and huge population density is also a factor."
While mountaintop removal is sometimes used by the mining industry, particularly in the US, researchers say the scale of this in China is unparalleled.
They warn that turning hills into plains is throwing dust particles into the atmosphere, polluting waterways, causing landslides and flooding and endangering plants and animals.
They add that the flattened land could also be unsuitable to build on.
Prof Li explained: "The most concerning issue is the safety of constructing cities on the newly created land.
"Yan'an, for example, is the largest project ever attempted on land that is composed of thick windblown silt.
"Such soft soils can subside when wet, causing structural collapse and land subsidence. Building on such soils is quite dangerous and it would take a very long time for the ground base to become stable."
The scientists say that the Chinese government should work with national and international experts to fully assess the risks before they continue....
Dr Jan Zalasiewicz, from the University of Leicester, added: "We're in new territory with these kinds of changes.
"There are other projects as well, like the Palm Island in Dubai, which is moving billions of tonnes of materials in one place to another to create a new landscape.
"And while humans have been doing that on a small to moderate scale for quite a long time, this is now exceeding the state of natural processes.""
6/4/14, "Environment: Accelerate research on land creation," Nature.com
"China's campaign to bulldoze mountains to build cities needs expertise to avert geoengineering problems, warn Peiyue Li, Hui Qian and Jianhua Wu."
Map of China from Nature.com