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Physical Processes in Earth and Environmental Sciences Phần 2

Chương 2 Magma có phân số nhỏ nhưng quan trọng của các chất khí hòa tan áp lực, bao gồm hơi nước. 5 sông nước có chứa chất rắn lơ lửng, trong khi bầu không khí mang theo các hạt bụi và bình xịt chất lỏng. | 20 Chapter 2 4 Magma has small but important fractions of pressurized dissolved gases including water vapor. 5 River water contains suspended solids while the atmosphere carries dust particles and liquid aerosols. 6 Seawater has c.3 percent by weight of dissolved salts and also suspensions of particulate organic matter. Solid Earth substances may break or flow 1 Ice fragments when struck yet deformation of boreholes drilled to the base of glaciers also shows that the ice there flows while cracking along crevasses at the surface. 2 Earth s mantle imaged by rapidly transmitted seismic waves behaves as a solid mass of crystalline silicate minerals. Yet there is ample evidence that in the longer term 103 years it flows convecting most of Earth s internal heat production as it does so. Even the rigid lower crust is thought to flow at depth given the right temperature and water content. 2.1.5 Timescales of in situ reaction The lesson from the last of the above examples is that we must appreciate characteristic timescales of reaction of Earth materials to imposed forces and be careful to relate state behavior to the precise conditions of temperature and pressure where the materials are found in situ. 2.2 Thermal matters 2.2.1 Heat and temperature Heat is a more abstract and less commonsense notion than temperature the use of the two terms in everyday speech being almost synonymous. We measure temperature with some form of heat sensor or thermometer. It is a measure of the energy resulting from random molecular motions in any substance. It is directly proportional to the mean kinetic energy that is mean product of mass times velocity squared Section 3.3 of molecules. Heat on the other hand is a measure of the total thermal energy depending again on the kinetic energy of molecules and also on the number of molecules present in any substance. It is through specific heat c that we can relate temperature and heat of any substance. Specific heat is a finite capacity sometimes .