What Is Isostacy?

Our Earth was formed 4.6 Billion years ago. This formation is partly due to the colliding of tectonic plates found under the Earth’s crust. These plates have greatly impacted the way in which the Earth’s outer layer looks and the type of terrain found across its vast surface. One example of these plates at work are volcanoes. Volcanoes are formed through the process of volcanism. This process occurs when “magma- a mixture of molten rock, suspended mineral grains, and dissolved gases formed in Earth 's interior — is forced to the surface.” (Reed,2013) The concept of isostacy is the “ideal theoretical balance of all portions of Earth’s lithosphere as though they were floating on the denser underlying layer is isostacy.” (Reed, 2013) When considering

For example, in the Earth’s crust there is a limit to the total weight each point of the Earth’s surface should meet. In mathematical terms, this concept of equilibrium is defined by the “depth of compensation” which is about 70 miles below the Earth’s surface. In short, for the Earth’s crust to hold equal mass and pressure, there must be an equal amount of mass everywhere. Isostacy controls the local and regional elevation levels of continents and the ocean floor in incongruence with the total weight their underlying rocks can maintain. Often times, this phenomena and the behavior exhibited by the plates is compared to an iceberg floating at sea in which the greater mass is submerged. Additionally, gravity plays a huge part in understanding the amount of pressure the surface must undergo in order to make such movements occur. For example, as gravity pushes down on the Earth, the plates begin to move causing isostacy to create equilibrium across the entirety of the planet. For years, scientists have attempted to explain why this phenomena occurs in relation to the thickness of the earth, gravity and land density. Not until scientists John Fillmore Hayford and John William Bowie did we have a concrete understanding of isostacy and its processes. Hayford and Bowie “were able to prove that the anomalies in gravity relate directly to topographic features. This essentially validated the idea of isostasy, and Hayford and Bowie further established the concept of the depth of isostatic compensation. Both gentlemen published books on isostasy and geodesy. Hayford was the first to estimate the depth of isostatic compensation and to establish that Earth has an oblate spherical shape (a bowed or ellipsoid sphere) rather than a true sphere.” (Editors of Encyclopedia Britannica,