Sea Level and Dry Land
Several terms are used to describe the changing relationships between sea level and dry land. When the term "relative" is used, it means change relative to a fixed point in the sediment pile. The term "eustatic" refers to global changes in sea level relative to a fixed point, such as the centre of the earth, for example as a result of melting ice-caps. The term "steric" refers to global changes in sea level due to thermal expansion and salinity variations. The term "isostatic" refers to changes in the level of the land relative to a fixed point in the earth, possibly due to thermal buoyancy or tectonic effects; it implies no change in the volume of water in the oceans. The melting of glaciers at the end of ice ages is one example of eustatic sea level rise. The subsidence of land due to the withdrawal of groundwater is an isostatic cause of relative sea level rise. Paleoclimatologists can track sea level by examining the rocks deposited along coasts that are very tectonically stable, like the east coast of North America. Areas like volcanic islands are experiencing relative sea level rise as a result of isostatic cooling of the rock which causes the land to sink.
On other planets that lack a liquid ocean, planetologists can calculate a "mean altitude" by averaging the heights of all points on the surface. This altitude, sometimes referred to as a "sea level", serves equivalently as a reference for the height of planetary features.
Read more about this topic: Eustatic
Famous quotes containing the words dry land, sea, level, dry and/or land:
“He who constantly swims in the ocean loves dry land.”
—Anton Pavlovich Chekhov (1860–1904)
“This fabulous shadow only the sea keeps.”
—Hart Crane (1899–1932)
“No man loses ever on a lower level by magnanimity on a higher.”
—Henry David Thoreau (1817–1862)
“Those who are esteemed umpires of taste, are often persons who have acquired some knowledge of admired pictures or sculptures, and have an inclination for whatever is elegant; but if you inquire whether they are beautiful souls, and whether their own acts are like fair pictures, you learn that they are selfish and sensual. Their cultivation is local, as if you should rub a log of dry wood in one spot to produce fire, all the rest remaining cold.”
—Ralph Waldo Emerson (1803–1882)
“I see an America whose rivers and valleys and lakes, hills and streams and plains; the mountains over our land and nature’s wealth deep under the earth, are protected as the rightful heritage of all the people.”
—Franklin D. Roosevelt (1882–1945)