1. Main Idea Magma Eruption
1. Does all magma erupt at the surface?

2. Main Idea Magma Eruption
2. Why does it matter where magma erupts or where it cools?

3. Main Idea Magma Eruption
3. How could you tell if there were an active magma intrusion below the surface?

4. 18.3 – Intrusive Activity

5. Plutons
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

6. 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

7. 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.

8. Sills Pluton that forms when magma intrudes parallel rock layers

9. Dikes
Pluton that cuts across preexisting rocks and often forms when magma invades cracks in surrounding rock bodies

10. 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.

11. 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.