Posts Tagged ‘sea’

What is the difference between a sea and a lake? (Environment Canada)

Friday, December 11th, 2009

[Editor's note: This Q&A from Environment Canada explains the rough difference between types of hydrological features. Names in the real world are often messier than this text book explanation. One way we've tried to help in Natural Earth is by indicating if a lake is freshwater, saline, natural, artificial, stable water level, seasonal water level, or simply ephemeral.]

Republished from Environment Canada. Feb. 2002.

What is the difference between a sea and a lake? Looking at the names of many sea and many lakes does not readily demonstrate an identifiable difference. There are salt water lakes and fresh water seas and some lakes that are bigger than other seas.
Bruce Schoenegge, Irvine, California, USA

Salt crust resulting from receding lake, Lake Frome, Australia.
Salt crust resulting from receding lake, Lake Frome, Australia.

In order to understand why some smaller salt water bodies are called lakes and others seas it is necessary to realize that lakes are, in geological time scales, transitory in nature–they form, mature and die.

Some water bodies that started out as saltwater seas over time became closed-off from the oceans. Depending on the quantity of fresh water flowing in from rivers, glacial melt water, or other sources, the salinity could have declined to the point where the water became relatively fresh. The Sea of Aral is probably an example of where this transition has occurred. Similarly the reverse can occur whereby freshwater lakes can become open to the sea so that the salinity increases, as in the Baltic Sea. The Black Sea is an example that has alternated between fresh and salt water conditions over geological time. Evidence for these changes can be found in ancient fossils of organisms some of which were known to be tolerant of saltwater while others were known to have been intolerant.

No doubt there was also some confusion in the naming of water bodies by the early explorers based on their first impressions and certainly one can understand why some may have been inappropriately named. In addition the subsequent translation of the names between different languages could also have added to the confusion.

Here are some definitions of water bodies:

Ocean
The whole body of salt water that covers nearly 3/4 of the surface area of the globe. In particular, each of the main areas into which the sea is divided geographically, e.g. Atlantic, Pacific. Oceans are tidal, living systems containing a multitude of biological organisms.

  • Average depth of the world’s oceans: 3,962 metres(13,000ft)
  • Maximum depth: 10,680 meters; (35,040ft)
  • Average salt content – 3.5% (mostly common salt, NaCl but with some magnesium and calcium salts)
  • Average density – 1.026
Sea
The expanse of salt water that covers most of the earth’s surface and surrounds the land masses. A body of salt water that is secondary in size to oceans.
Lake
A large area of water surrounded by land. Normally fresh water but in some cases can be appreciably saline depending on the geology of the underlying and surrounding terrain. Lakes are living systems containing various quantities of biological organisms. Lakes can be classified according to the level of bioproductivity as oligotrophic (low productivity), mesotrophic or eutrophic (high productivity). The productivity is usually controlled by the amount of nutrients (mostly phosphorus and nitrogen) present in the water and the amount of light that can penetrate the water column.
River
A large natural stream of water flowing in a channel to the sea, a lake or another such river. The flow can be permanent of seasonal.
Stream
A small, narrow river flowing on the surface of, or beneath, the ground.

Maya Lin: Systematic Landscapes (Corcoran in Washington, DC)

Friday, June 12th, 2009

[Editor's note: If you travel to DC this summer, check out this installation from renowned contemporary artist and architect Maya Lin of the Vietnam Veterans Memorial fame. There is a fee to enter the private museum.]

Republished from the Corcoran Gallery of Art, Washington D.C.

Run dates: March 14, 2009 — July 12, 2009

This spring, the Corcoran Gallery of Art will present Maya Lin: Systematic Landscapes—a dramatic installation of major new works by this renowned contemporary artist and architect.   On view from March 14 through July 12, the exhibition addresses contemporary ideas about landscape and geologic phenomena.  Lin’s second nationally-traveling exhibition in 10 years, Systematic Landscapes explores how people perceive and experience the landscape in a time of heightened technological influence and environmental awareness.

Lin (b. 1959) came to prominence in 1981 with her design for the Vietnam Veterans Memorial in Washington, D.C. and has since achieved a high degree of recognition for a body of work that includes monuments, buildings, earthworks, sculpture and installations.  Traversing Lin’s constructed landscapes in this exhibition—moving around, under, and through them—we encounter a world that has been mapped, digitized, analyzed, and then reintroduced by Lin as actual, physical structures.  Her work blends a typology of natural forms, from rivers to mountains to seas, with a visual language of scientific analysis represented by grids, models, and maps.  In doing so, Lin merges an understanding of the ideal and the real, encouraging an encounter with conceptual, sculptural and architectural modeling.

Systematic Landscapes is centered on a trio of large-scale sculptural installations: 2×4 Landscape (2006), Water Line (2006) and Blue Lake Pass (2006).  Each sculpture offers a different means for viewers to engage with and comprehend a schematic representation of landscape forms.  In these projects, Lin examines how people’s modern relationships to the land are extended, condensed, distorted and interpreted through new computer technologies.  She translates a series of dramatic landscape environments selected for their inspiring beauty and connection to life-supporting habitats into spatial environments where viewers can engage with them in an art gallery setting.

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