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35-434: A blockfield (also spelt block field ), felsenmeer , boulder field or stone field is a surface covered by boulder- or block-sized rocks usually associated with a history of volcanic activity, 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

70-562: A desert , or so called polar desert ), averaging 166 millimetres (6.5 in) of precipitation per year, as weather fronts rarely penetrate far into the continent. Summits of most mountains also have polar climates, despite being in lower latitudes, due to their high elevations. All mountains of the Rocky Mountains , Alps , and the Caucasus have tundra climate. Some mountains of the Andes ,

105-604: A characteristic pressure-temperature curve. As the pressure gets lower, the temperature decreases. The rate of decrease of temperature with elevation is known as the adiabatic lapse rate , which is approximately 9.8 °C per kilometer (or 5.4 °F per 1000 feet) of altitude. The presence of water in the atmosphere complicates the process of convection. Water vapor contains latent heat of vaporization . As air rises and cools, it eventually becomes saturated and cannot hold its quantity of water vapor. The water vapor condenses (forming clouds ), and releases heat, which changes

140-543: 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. Felsenmeers only form on slopes of 25° or lower. A steeper angle results in transport of

175-551: A lack of warm summers but with varying winters . Every month a polar climate has an average temperature of less than 10 °C (50 °F). Regions with a polar climate cover more than 20% of the Earth's area. Most of these regions are far from the equator and near the poles , and in this case, winter days are extremely short and summer days are extremely long (they could last for the entirety of each season or longer). A polar climate consists of cool summers and very cold winters (or, in

210-583: 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. Due to the slope requirements they are most commonly found on plateaus . Basalt and sedimentary rocks often produce larger, more numerous felsenmeers than other types of rock. Blockfields are most often found in high mountain periglacial regions near

245-491: A mountain is roughly equivalent to moving 80 kilometres (50 miles or 0.75° of latitude ) towards the pole. This relationship is only approximate, however, since local factors, such as proximity to oceans , can drastically modify the climate. As the altitude increases, the main form of precipitation becomes snow and the winds increase. The temperature continues to drop until the tropopause , at 11,000 metres (36,000 ft), where it does not decrease further. This

280-508: A polar climate. Climatologist Wladimir Köppen demonstrated a relationship between the Arctic and Antarctic tree lines and the 10 °C (50 °F) summer isotherm; i.e., places where the average temperature in the warmest calendar month of the year is below the fixed threshold of 10 °C (50 °F) cannot support forests. See Köppen climate classification for more information. Otto Nordenskjöld theorized that winter conditions also play

315-455: A role: His formula is W = 9 − 0.1 C , where W is the average temperature in the warmest month and C the average of the coldest month, both in degrees Celsius. For example, if a particular location had an average temperature of −20 °C (−4 °F) in its coldest month, the warmest month would need to average 11 °C (52 °F) or higher for trees to be able to survive there as 9 − 0.1(−20) = 11 . Nordenskiöld's line tends to run to

350-490: Is above 0 °C (32 °F), while an ice cap climate has no months averaging above 0 °C (32 °F). In a tundra climate, even coniferous trees cannot grow, but other specialized plants such as the arctic poppy can grow. In an ice cap climate, no plants can grow, and ice gradually accumulates until it flows or slides elsewhere. Many high altitude locations on Earth have a climate where no month has an average temperature of 10 °C (50 °F) or higher, but as this

385-586: Is almost surrounded by landmasses like Russia and Canada . As such, the climate of much of the Arctic is moderated by the ocean water, which can never have a temperature below −2 °C (28 °F). In winter, this relatively warm water, even though covered by the polar ice pack , keeps the North Pole from being the coldest place in the Northern Hemisphere , and it is also part of the reason that Antarctica

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420-503: Is between 1.5 and 3 °C (34.7 and 37.4 °F). The alpine climate in Holdridge system is roughly equivalent to the warmest tundra climates (ET) in the Köppen system. b) the alvar climate, the coldest mountain climate since the biotemperature is between 0 °C and 1.5 °C (biotemperature can never be below 0 °C). It corresponds more or less to the coldest tundra climates and to

455-541: Is divided by the number of all temperatures (including both adjusted and non-adjusted ones). The variability of the alpine climate throughout the year depends on the latitude of the location. For tropical oceanic locations, such as the summit of Mauna Loa , the temperature is roughly constant throughout the year. For mid-latitude locations, such as Mount Washington in New Hampshire , the temperature varies seasonally, but never gets very warm. The temperature profile of

490-478: Is due to elevation, this climate is referred to as Alpine climate . Alpine climate can mimic either tundra or ice cap climate. On Earth, the only continent where the ice cap polar climate is predominant is Antarctica . All but a few isolated coastal areas on the island of Greenland also have the ice cap climate. Summits of many high mountains also have ice cap climate due to their high elevation. Coastal regions of Greenland that do not have permanent ice sheets have

525-932: Is higher than the highest summit . Although this climate classification only covers a small portion of the Earth's surface, alpine climates are widely distributed. They are present in the Himalayas , the Tibetan Plateau , Gansu , Qinghai and Mount Lebanon in Asia ; the Alps , the Urals , the Pyrenees , the Cantabrian Mountains and the Sierra Nevada in Europe ; the Andes in South America ;

560-406: Is hot, it tends to expand, which lowers its density. Thus, hot air tends to rise and transfer heat upward. This is the process of convection . Convection comes to equilibrium when a parcel of air at a given altitude has the same density as its surroundings. Air is a poor conductor of heat, so a parcel of air will rise and fall without exchanging heat. This is known as an adiabatic process , which has

595-432: Is so much colder than the Arctic. In summer, the presence of the nearby water keeps coastal areas from warming as much as they might otherwise, just as it does in temperate regions with maritime climates . The climate of Antarctica is the coldest on Earth. Antarctica has the lowest naturally occurring temperature ever recorded: −93.3 °C (−135.9 °F) at Vostok Station . It is also extremely dry (technically

630-620: The Drake Passage ) and such subantarctic islands such as the South Shetland Islands and the Falkland Islands have tundra climates of slight temperature range in which no month is as warm as 10 °C (50 °F). These subantarctic lowlands are found closer to the equator than the coastal tundras of the Arctic basin. Summits of many mountains of Earth also have polar climates, due to their higher elevations. Some parts of

665-699: 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

700-498: The Köppen climate classification , the alpine and mountain climates are part of group E , along with the polar climate , where no month has a mean temperature higher than 10 °C (50 °F). According to the Holdridge life zone system, there are two mountain climates which prevent tree growth : a) the alpine climate, which occurs when the mean biotemperature of a location

735-788: The Saint Elias Mountains , and most mountains of the Himalayas , the Karakoram , the Hindu Kush Range , Pamir Mountains , the Tian Shan Mountains , and the Alaska Range also have ice cap climates at extremely high elevations, in addition to tundra climates at relatively lower elevations. Only the summit of Mount Rainier has an ice cap climate in the Cascade Range . There have been several attempts at quantifying what constitutes

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770-825: The Sierra Nevada , the Cascade Range , the Rocky Mountains , the northern Appalachian Mountains ( Adirondacks and White Mountains ), and the Trans-Mexican Volcanic Belt in North America ; the Southern Alps in New Zealand ; the Snowy Mountains in Australia ; high elevations in the Atlas Mountains , Ethiopian Highlands , and Eastern Highlands of Africa ; the central parts of Borneo and New Guinea ; and

805-410: The ice cap climates (EF) as well. Holdrige reasoned that plants net primary productivity ceases with plants becoming dormant at temperatures below 0 °C (32 °F) and above 30 °C (86 °F). Therefore, he defined biotemperature as the mean of all temperatures but with all temperatures below freezing and above 30 °C adjusted to 0 °C; that is, the sum of temperatures not adjusted

840-471: The Antarctic under Köppen's. In 1947, Holdridge improved on these schemes , by defining biotemperature : the mean annual temperature, where all temperatures below 0 °C or 32 °F (and above 30 °C or 86 °F) are treated as 0 °C (because it makes no difference to plant life, being dormant). If the mean biotemperature is between 1.5 and 3 °C (34.7 and 37.4 °F), Holdridge quantifies

875-741: The Arctic Circle, especially in Iceland , the Canadian arctic and Norway and are still active in parts of Central Europe that were not covered by ice sheets. In the Southern Hemisphere inactive blockfields can be found in the Lesotho Highlands , and the Prince Edward Islands . Felsenmeers are, typically, relatively young geomorphological features. Most felsenmeers formed during or since

910-602: The Arctic are covered by ice ( sea ice , glacial ice , or snow ) year-round, especially at the most poleward parts; and nearly all parts of the Arctic experience long periods with some form of ice or snow on the surface. Average January temperatures range from about −40 to 0 °C (−40 to 32 °F), and winter temperatures can drop below −50 °C (−58 °F) over large parts of the Arctic. Average July temperatures range from about −10 to 10 °C (14 to 50 °F), with some land areas occasionally exceeding 30 °C (86 °F) in summer. The Arctic consists of ocean that

945-471: The atmosphere is a result of an interaction between radiation and convection . Sunlight in the visible spectrum hits the ground and heats it. The ground then heats the air at the surface. If radiation were the only way to transfer heat from the ground to space, the greenhouse effect of gases in the atmosphere would keep the ground at roughly 333 K (60 °C; 140 °F), and the temperature would decay exponentially with height. However, when air

980-452: The blocks due to gravity. This creates a talus slope, rather than a felsenmeer. Crude sorting with boulder imbrication can occasionally be seen on the surface of felsenmeers. 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

1015-416: The case of ice cap climates, no real summer at all), which results in treeless tundras , glaciers , or a permanent or semi-permanent layer of ice . It is identified with the letter E in the Köppen climate classification . There are two types of polar climate: ET , or tundra climate ; and EF , or ice cap climate . A tundra climate is characterized by having at least one month whose average temperature

1050-440: The lapse rate from the dry adiabatic lapse rate to the moist adiabatic lapse rate (5.5 °C per kilometre or 3 °F per 1000 feet). The actual lapse rate, called the environmental lapse rate , is not constant (it can fluctuate throughout the day or seasonally and also regionally), but a normal lapse rate is 5.5 °C per 1,000 m (3.57 °F per 1,000 ft). Therefore, moving up 100 metres (330 ft) on

1085-419: The last ice age (approximately 20,000 years ago). Others may be pre-glacial features that survived glaciation beneath cold-based glaciers. Their specific age can be determined using surface exposure dating , a technique that works best on materials which have been exposed to cosmic rays with little interference from trees or soils. Alpine climate There are multiple definitions of alpine climate. In

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1120-568: The less extreme tundra climates. The northernmost part of the Eurasian land mass, from the extreme northeastern coast of Scandinavia and eastwards to the Bering Strait , large areas of northern Siberia and northern Iceland have tundra climate as well. Large areas in northern Canada and northern Alaska have tundra climate, changing to ice cap climate in the most northern parts of Canada. Southernmost Argentina ( Tierra del Fuego where it abuts

1155-579: The north of Köppen's near the west coasts of the Northern Hemisphere continents, south of it in the interior sections, and at about the same latitude along the east coasts of both Asia and North America. In the Southern Hemisphere, all of Tierra del Fuego lies outside the polar region in Nordenskiöld's system, but part of the island (including Ushuaia , Argentina ) is reckoned as being within

1190-639: The summits of Mount Pico in the Atlantic and Mauna Loa in the Pacific . The lowest altitude of alpine climate varies dramatically by latitude. If alpine climate is defined by the tree line, then it occurs as low as 650 metres (2,130 ft) at 68°N in Sweden, while on Mount Kilimanjaro in Tanzania, the tree line is at 3,950 metres (12,960 ft). Polar climate The polar climate regions are characterized by

1225-587: The surface. An alternative theory 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,

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