There are three main sources of heat in the deep earth: (1) heat from when the planet formed and accreted, which has not yet been lost; (2) frictional heating, caused by denser core material sinking to the center of the planet; and (3) heat from the decay of radioactive elements. CROSS SECTION shows Earth's structure.
â The operating margin was an especially useful metric or ratio during the meeting as we wanted the discussion to include revenue statistics.
ARM Margin. DEFINITION of 'ARM Margin'. A fixed percentage rate that is added to an index value to determine the fully indexed interest rate of an adjustable rate mortgage (ARM). The margin is constant throughout the life of the mortgage, while the index value is variable.