18.2: INTRUSIVE ACTIVITY SWBATS:

VOCABULARY TO KNOW: Igneous rock Intrusive igneous rock Extrusive igneous rock Metamorphic rock Sedimentary rock

18. 2: INTRUSIVE ACTIVITY 1. How does the magma affect the crust 18.2: INTRUSIVE ACTIVITY 1. How does the magma affect the crust? (Hint: answer is in the 1st paragraph) Magma can force the overlying rock apart and enter the newly formed fissure (crack) Magma can cause blocks of rock to break off and sink in to the magma – rocks may eventually melt. Magma can melt the rock that it intrudes

2. What is a pluton? How are plutons classified? Pluton: intrusive igneous rock bodies, including batholiths, stocks, sills, and dikes, formed through mountain-building processes and oceanic-oceanic collisions; can be exposed at Earth’s surface due to uplift and erosion. Plutons are classified based on their size, shape and relationship to surrounding rock.

3. What is the difference between batholiths and stocks 3. What is the difference between batholiths and stocks? Give an example of each. Batholiths: Coarse-grained, irregularly shaped, igneous rock mass that covers at least 100 km2, generally forms 10-30km below Earth’s surface, and is common in the interior major mountain chains. EX: Coast Range Batholith in British Columbia Stocks: irregularly shaped pluton that is similar to a batholith but smaller, generally forms 10-30 km beneath Earth’s surface, and cuts across older rocks.

4. What is a laccolith? Give an example of a laccolith. Laccolith: relatively small, mushroom-shaped pluton that forms when magma intrudes into parallel rock layers close to Earth’s surface. EX: Black Hills of South Dakota, Henry Mountains of Utah, and the Judith Mountains of Montana.

5. What is the difference between sills and dikes 5. What is the difference between sills and dikes? Give an example of each. Sills: pluton that forms when magma intrudes parallel rock layers. Magma squeezed into horizontal cracks between rock layers and hardens EX: Palisades Sill, New York Dikes: pluton that cuts across preexisting rocks and often forms when magma invades crakes in surrounding rock bodies. EX: The Great Dike, Zimbabwe, Africa

6. Why are the do the textures of sills and dikes vary 6. Why are the do the textures of sills and dikes vary? Why are many of them coarse grained? The textures of sills and dikes vary due to the rate at which the magma cooled. Coarse grained = slow cooling Fine grained = rapid cooling Many sills and dikes are coarse grained because they are thought to have formed deep in Earth’s crust where magma cooled slowly which produced large mineral grains.

7. Describe the connection between plutons and tectonics. Plutons form as a result of mountain building process. Oceanic-continental convergence and Oceanic-oceanic convergence Subduction zones create areas of melted rock that cooled below earth’s crust to form batholiths.

8. Where would you find plutons in California 8. Where would you find plutons in California? How were they created and why are we able to view them? Batholiths are then exposed as a result of uplift and erosion. EX: Sierra Nevada Batholith and Yosemite National Park