From the German
for "rock sea
", a felsenmeer, also called a blockfield
is a land form which develops in cold climates
, by the process of frost wedging
; the shattering of rocks by the freezing
of water in tiny cracks. Basically, geologists
come along find a bunch of cubes
and rectangular prisms
on top of entire fields of bedrock
, with no cliff face nearby to explain their presence. Usually, felsenmeer is found in flat
elevations, or in sub-polar
areas, where the water can freeze, and then thaw out to freeze again.
These rocks remain fairly large (up to 4m to a side), rather than breaking into smaller and smaller pieces, because much of the silt which they develop is washed away with the spring thaw. Consequently, with the spaces opened up, the rock cubes do not freeze as one solid chunk.
Generally, felsenmeer will be formed of limestone, basalt or granite, because these rocks tend not to slip around, and if they were to slip around, they would no longer remain in place, and could no longer be refered to as block field - becoming, rather, a block flow.
Where felsenmeer may be found in particular is in the Baltic and Canadian Shields, due to the combination of climate and geological makeup.