The term felsenmeer comes from the German meaning 'sea of rock'. In a felsenmeer (also known as a block field), freeze-thaw weathering has broken up the top layer of the rock, covering the underlying rock formation with jagged, angular bolders. Freeze-thaw 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.

Surface

Felsenmeers only form on slopes of 25° or lower. A steeper angle results in transport of the blocks due to gravity. This creates a talus

Scree

Scree, also called talus, is a term given to an accumulation of broken rock fragments at the base of crags, mountain cliffs, or valley shoulders. Landforms associated with these materials are sometimes called scree slopes or talus piles...

 slope, rather than a felsenmeer. Crude sorting with boulder imbrication

Imbrication

' is the arrangement of planar bodies such that they stack in a consistent fashion - rather like a toppled run of dominoes.*In roofing, imbrication is employed in the Imbrex and tegula system.*Imbrication ....

 can occasionally be seen on the surface of felsenmeers.

Profile

The depth of the boulder field depends on the slope angle, rock types, age, and erosional history. However, a reasonable average for felsenmeer depth is approximately 1m. Ballantyne (1998) defines three types of felsenmeer profiles:
Type 1 consists of boulders overlying a matrix of fines at some depth below the surface.
Type 2 consists of boulders supported by a cohesionless sandy matrix that continues from the surface down through the profile.
Type 3 also consists of boulders supported by a matrix, but differs from Type 2 in that the matrix consists of silt and/or clay rather than sand.

Occurrence

Felsenmeers are most often found in high mountain periglacial

Periglacial

Periglacial is an adjective originally referring to places in the edges of glacial areas, but it has later been widely used in geomorphology to describe any place where geomorphic processes related to freezing of water occur...

 regions near the Arctic Circle, especially in Iceland

Iceland

Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...

, the Canadian

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 arctic and Norway

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

. Due to the slope requirements they are most commonly found on plateaus. Basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

 and sedimentary rock

Sedimentary rock

Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....

s often produce larger, more numerous felsenmeers than other types of rock.

Age

Felsenmeers are, typically, relatively young geomorphological features. Most felsenmeers formed during or since last ice age

Ice age

An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

 (approximately 20,000 years ago). Their specific age can be determined using surface exposure dating

Surface exposure dating

Surface exposure dating is a collection of geochronological techniques for estimating the length of time that a rock has been exposed at or near Earth's surface. Surface exposure dating is used to date glacial advances and retreats, erosion history, lava flows, meteorite impacts, rock slides, fault...

, a technique that works best on materials which have been exposed to cosmic rays with little interference from trees or soils.