Metamorphic rocks formed by contact metamorphism are usually not as dense as ones formed by regional metamorphism because?????????/
2007-11-19 07:57:07 · 3 answers · asked by toocute4that 2 in Science & Mathematics ➔ Earth Sciences & Geology
The real reasons are due to pressures exerted by regional metamorphism. Contact metamorphism is always under low pressure when compared to regional metamorphism. Higher pressures have the effect of driving out less dense volatiles, such as water vapor or carbon dioxide. Increased pressure can result in phase changes in minerals due repacking of atoms within the mineral structure (example: graphite and diamond are polymorphs of carbon, but diamond is denser). Finally, when minerals form they have imperfections due to impurities. These imperfections are sometimes manifested as "holes". Increased pressure forces these holes out of the crystalline structure by processes called "screw dislocations" and "glide dislocations". When holes are filled in, the mineral becomes denser.
2007-11-19 13:40:53 · answer #1 · answered by Amphibolite 7 · 0⤊ 0⤋
Contact metamorphism just affects a small number of rocks,but the regional metamorphism is spread over a region. Heat produced is lower compared to the high heat produced by the regional metamorpism. Pressure too varies in both. These both factors affect the structure, density.
So rocks formed by regional metamorphism is denser than the rock formed by contact metamorphism
2007-11-19 16:40:40 · answer #2 · answered by Anonymous · 0⤊ 0⤋
For equivalent temperatures, regional metamorphism is under much higher pressure.
2007-11-19 17:09:00 · answer #3 · answered by busterwasmycat 7 · 0⤊ 0⤋