An intrusion is an igneous rock body that forms from crystallized magma under Earth's surface.any mountain ranges, such as the Sierra Nevada in California, are formed mostly by intrusive rock, large granite (or related rock) formations. Intrusions are one of the two ways igneous rock can form; the other is extrusive, that is, a volcanic eruption or similar event.
Admit it: you were pronouncing the word âSmaugâ â the name of the Hobbit dragon, the one whoâs in the subtitle of the upcoming movie installation â as âsmog.â.
â Bilbo Baggins, to himself. Smaug (birth unknown â Third Age 2941) was the greatest fire-breathing dragon of the Third Age. Details of his origin are unknown, but in T.A. 2770 he attacked the Lonely Mountain and the town of Dale.ike all dragons, Smaug-described by Thorin as  a most specially greedy, strong and wicked worm  - loves to hoard gold with a meticulous knowledge of his own collection as evidenced by his immediate spotting of the missing cup.