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.
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Famous quotes containing the words sea, level, dry and/or land:
“For half a mile from the shore it was one mass of white breakers, which, with the wind, made such a din that we could hardly hear ourselves speak.... This was the stormiest sea that we witnessed,—more tumultuous, my companion affirmed, than the rapids of Niagara, and, of course, on a far greater scale. It was the ocean in a gale, a clear, cold day, with only one sail in sight, which labored much, as if it were anxiously seeking a harbor.... It was the roaring sea, thalassa exeessa.”
—Henry David Thoreau (1817–1862)
“It is only for a little while, only occasionally, methinks, that we want a garden. Surely a good man need not be at the labor to level a hill for the sake of a prospect, or raise fruits and flowers, and construct floating islands, for the sake of a paradise. He enjoys better prospects than lie behind any hill. Where an angel travels it will be paradise all the way, but where Satan travels it will be burning marl and cinders.”
—Henry David Thoreau (1817–1862)
“A woman moved is like a fountain troubled.
Muddy, ill-seeming, thick, bereft of beauty,
And while it is so, none so dry or thirsty
Will deign to sip or touch one drop of it.”
—William Shakespeare (1564–1616)
“I traveld thro’ a Land of Men
A Land of Men & Women too,
And heard & saw such dreadful things
As cold Earth wanderers never knew.”
—William Blake (1757–1827)