The lack of oxygen in a peat bog prevents dead plants from decomposing. This results in an accumulation of organic matter, creating a sort of spongy earth that is referred to as peat moss. This peat moss was once extracted in bricks and dried during good weather. It was used as fuel, in wood burners when wood was sparse in the Jura. This exploitation continued for many centuries. Deep trenches are still visible in the Jura peat bogs, ensuring that the peat that has not been exploited dries out.