Felsenmeer

A blockfield (also spelt block field) felsenmeer,boulder field or stone field is a surface covered by boulder- or block-sized angular rocks usually associated with alpine and subpolar climates and periglaciation. Blockfields differ from screes and talus slope in that blockfields do not apparently originate from mass wastings. They are believed to be formed by frost weathering below the surface. An alternative theory suggests that modern blockfields may have originated from chemical weathering that occurred in the Neogene when the climate was relatively warmer. Following this thought the blockfields would then have been reworked by periglacial action.

Most known blockfields are located in the northern hemisphere. Examples can be found in Abisko National Park in Sweden, Snowdonia National Park in Wales, the Great End-Scafell Pike ridge in England and Hickory Run Boulder Field and River of Rocks in the Appalachian Mountains of the United States. All examples except the first one are outside present day subpolar climate areas, and have thus traditionally been seen as relict landforms from past times when these areas were under periglaciation.

The term "felsenmeer" comes from the German meaning 'sea of rock'. In a felsenmeer or blockfield, freeze-thaw weathering has broken up the top layer of the rock, covering the underlying rock formation with jagged, angular boulders. Freeze-thaw or frost weathering occurs when water that is trapped along microcracks in rock expands and contracts due to fluctuations in temperature above and below the freezing point. Felsenmeers are formed in situ, meaning that they are not transported during or after their creation.

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