Unless you want to replace every article link in the encyclopaedia with a little footnote explaining what the term means then your stance doesnt make sense  Footnotes which take readers away from the text of the article are not very helpful and there is no support in the MOS for the use of footnotes in this way If you think that people generally wont understand what a lahar is and cannot simply click on the link to an article then a short explanation of the geological activity that led to the disaster would be an infinitely better means of dealing with that  At the moment its only briefly mentioned in the lead