Mima mounds puzzle solved? These enigmatic mounds have puzzled geologists for decades, with many hyp

Mima mounds puzzle solved? These enigmatic mounds have puzzled geologists for decades, with many hypotheses advanced for their method of formation. They consist of areas of low flattened domes of thickened topsoil, often incorporating gravel. They vary from 3 to 50 metres in diameter and from 30cm to over 2 meters high, and can be as dense as 50 per hectare (nearly 2.5 acres). They often occur in prairie areas with a shallow basement beneath the soil layers. They are also called hog wallow or prairie mounds. They occur at times in millions, covering wide swaths of landscape. Ideas about their formation include the accumulation of wind borne sediment in small dunes around clumps of vegetation during long droughts, glacial era freeze-thaw cycles, seismic activity shaking up the ground into this pattern created by the pattern in the energy waves, and the shrinking swelling cycle of clay minerals during alternating dry and wet periods. A last possibility, and the one supported by rent research just presented at this year’s AGU meeting, is that they are the result of the activity patterns of burrowing rodents tunneling upwards when they encounter the shallow basement and can’t dig any deeper Scientists from San Jose State University modelled the results of many digital gophers moving soil in these geological conditions while burrowing over many generations, and mima mounds started to spread in the same configurations as found in nature across the virtual landscape. In areas with shallow basements the soil is often waterlogged, and the gophers move earth upwards in order to stay dry and above the water table. These grow over generations into Mima mounds. The mounds occur worldwide, and while gophers are restricted to America, other burrowing animals fulfil their function in most terrestrial ecosystems. Loz Image credit: Washington State Departmenthttp://www.atlasobscura.com/places/mima-moundshttp://www.bbc.co.uk/news/science-environment-25259133 -- source link

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