Of course, this is balanced with gas content -- if the magma contains more gas bubbles, it will erupt more violently, and if it contains less gas, it will erupt more calmly.
A memorandum of understanding (MOU) is an agreement between two parties in the form of a legal document. It is not fully binding in the way that a contract is, but it is stronger and more formal than a traditional gentleman's agreement. Sometimes, the term is used as a synonym for a letter of intent, particularly in private law.
Essentially, TRu is an expression of contentment, satisfaction, goodness, approval, and/or of course, agreement. It is generally enunciated in a deep, low voice, with a slightly increasing pitch, and the vowel sound of u is elongated without the diphthong. TRu can also be used to fill a void in conversation.