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 sea, level, dry and/or land:
“And then the man whom Sorrow named his friend
Cried out, Dim sea, hear my most piteous story!
The sea swept on and cried her old cry still,
Rolling along in dreams from hill to hill.
He fled the persecution of her glory....”
—William Butler Yeats (1865–1939)
“The effort to understand the universe is one of the very few things that lifts human life a little above the level of farce, and gives it some of the grace of tragedy.”
—Steven Weinberg (b. 1933)
“If you are one of the hewers of wood and drawers of small weekly paychecks, your letters will have to contain some few items of news or they will be accounted dry stuff.... But if you happen to be of a literary turn of mind, or are, in any way, likely to become famous, you may settle down to an afternoon of letter-writing on nothing more sprightly in the way of news than the shifting of the wind from south to south-east.”
—Robert Benchley (1889–1945)
“Every time we get near the land you get that look on your face. When a man goes to sea, he ought to give up thinking about things on shore. Land don’t want him no more. I’ve had me share of things go wrong and all come from the land. Now I’m through with the land and the land’s through with me.”
—Dudley Nichols (1895–1960)