Much of the theoretical basis for cultural geography also rests on the core and
periphery spatial relationship. Perhaps obviously, the notions ofcultural hearths
and cultural diffusion carry an implied core and periphery dynamic. The cultural
core areas are those where cultural innovation emerges, which then diffuses to
the cultural hinterland surrounding the core. In addition, cultural core areas may
play a vital role in solidifyingcultural identity. The late Terry Jordan-Bychkov,
a leading cultural geographer in the United States, noted that the lack of a cultural
core area often left a void in the formation of cultural or national identity, and such
states frequently were politically unstable, because regions lying in the periphery
were not culturally bound to the state, and often formed allegiances to external cul-
tural influences. In states where a strong cultural core area exists, cultural identity
is likely to be stronger because the elements underpinning that identity diffuse to
the periphery and are incorporated by residents there. The core and periphery struc-
ture is also encountered in the study oflinguistic geography, another subfield of
cultural geography. Language regions rarely are characterized by distinct, clearly
definedboundaries. Rather, the geographical expression of a language is strongest
in a core area and then diminishes into a peripheral zone—the greater the distance
from the core area, the lower the instance of usage of the language in question. A
language may be spoken on a daily basis by 90 percent of the population in the core
areas, for example, but by only 10 percent in the periphery, where it is displaced by
another tongue, or is not spoken in the home, but only as a second language.Cryosphere
The term cryosphere comes from the Greek rootkryosand means “cold” or “frost.”
In physical geography, cryosphere is a general term referring to the worldwide
occurrence of frozen water in its snow and ice forms. These coldlandscapesand
seascapes are important on their own but also help to regulatetemperaturesfor
the planet as a whole. The high reflectivities of snow and ice are considerable greater
than liquid water and land surfaces, so they redirectsolar energyback toward space
preventing part of that energy from warming the surface via absorption. Snow and
ice are also direct determinants of sea level. Three-quarters ofEarth’s freshwater
is locked in ice, which covers about 10 percent of the land surface.
Cold temperatures allow water to freeze and this phase change is caused by
energy loss from strings of liquid water molecules to rigid crystalline configura-
tions. Pure water freezes at 0°C but seawater of average salinity does not freeze
until it reaches− 2 °C. Over much of the world, precipitation starts in clouds as
snow. If temperatures below the clouds are below freezing the precipitation is74 Cryosphere