Main Idea Magma Eruption 1. Does all magma erupt at the surface?
Main Idea Magma Eruption 2. Why does it matter where magma erupts or where it cools?
Main Idea Magma Eruption 3. How could you tell if there were an active magma intrusion below the surface?
18.3 – Intrusive Activity http://3dparks.wr.usgs.gov/2005/lakemead/images/volcanic.gif
Plutons http://www.geo.hunter.cuny.edu/bight/images/pluton.jpg Intrusive igneous rock body, including batholiths, stocks,sills & dikes Formed through mountain-building processes and oceanic-oceanic collisions Can be exposed at Earth’s surface to uplift and erosion
Batholiths & Stocks The largest plutons are called Batholiths. Batholiths are coarse-grained, irregularly shaped, igneous rock mass that covers at least 100 km2 Stocks are irregularly shaped plutons but smaller in size. Both generally form 5-30 km below Earth’s surface and are common in the interior of major mountain chains
Laccoliths Relatively small Mushroom-shaped pluton that forms when magma intrudes into parallel rock layers close to Earth’s surface Laccoliths have flat bottoms and curved tops. http://www.indiana.edu/~geol105/images/gaia_chapter_5/dike&sill.jpg
Sills Pluton that forms when magma intrudes parallel rock layers http://www.austmus.gov.au/geoscience/images/earth_diagrams/volcano_structure.gif
Dikes Pluton that cuts across preexisting rocks and often forms when magma invades cracks in surrounding rock bodies http://www.waipahums.k12.hi.us/eportfolio05-06/wisportfolio05-06/team8d_portfolios/y_kenneth_e_portfolio/volcano_files/image002.png
Plutons & Tectonics Many plutons form as the result of mountain-building processes. Plutons are thought to form as a result of continental-continental and oceanic-continental convergence.
Reinforcement T/F Batholiths are common in the interiors of mountain chains. Laccoliths have curved bottoms and flat tops. Sills form when magma is forced between rock layers. Most igneous activity occurs deep within earth.