1. Intrusive igneous activity
As magma cools underground, it will begin to solidify within Earth’s crust.
Once completely crystallized, these masses of igneous intrusive rock are referred to as INTRUSIONS or as PLUTONS
We will talk about several types of igneous plutons:
Dikes, Sills, Laccoliths, Batholiths, & Volcanic Necks

2. Intrusive igneous activity
Types of intrusive igneous features
Dike – relatively small igneous intrusions formed as magma penetrates into rock fractures and solidifies into thin, sheet-like bodies.
Sill – sheet-like intrusions, like dikes, but they tend to be much thicker, and form as magma intrudes in between layers of sedimentary rock, then cools. Not as common as dikes

3. Dike

4. Diabase dike cutting thru preCambrian age Hakatai Shale at Hance Rapid in the Grand Canyon.

5. Sill

6. A sill in the Salt River Canyon, Arizona

7. Laccolith
Begins as a sill, since material fills in between rock layers.
Because of pressure, some sills can arch up the overlying sediments, creating a mushroom shaped rock body .
Tend to form at shallow depths

8. Laccolith

9. Intrusive igneous activity
Intrusive igneous features continued
Batholith
Large plutons lacking a specific shape
Form as huge quantities of magma intrude into country rock, remove fragmets, and melt their way towards the surface.
Most remains underground
Large batholiths can be over 100 miles across

10. When batholiths are uplifted and exposed, they are usually resistant strata that form the roots of mountain ranges or eroded highlands.

11. Batholiths
of western
North
America

12. Batholith

13. Intrusive Igneous Activity
Volcanic pipes and necks
Pipes - short conduits that connect a magma chamber to the surface
Volcanic necks (e.g., Ship Rock, New Mexico) - resistant vents left standing after erosion has removed the volcanic cone

14. Formation of a volcanic neck

15. The most famous volcanic neck in the United States is Shiprock, New Mexico

17. Igneous Intrusions

18. Volcanoes & Plate Tectonics
Most volcanoes occur in the area known as the Ring of Fire
Volcanoes can form at CONVERGENT & DIVERGENT plate boundaries!!
Volcanoes can also occur within a plate which can result in hot spots and form Island chains like Hawaii & Iceland

19. A. Rising mantle plume; B
A. Rising mantle plume; B. Rapid decompression melting producing flood basalts; and C. Rising plume tail produced by linear seafloor volcanic chain

20. Distribution of some of the world’s major volcanoes

21. Volcanoes and climate The basic premise
Explosive eruptions emit huge quantities of gases (SO2) and fine-grained debris
A portion of the incoming solar radiation is reflected and filtered out
Past examples of volcanism affecting climate
Mount Tambora, Indonesia – 1815
Krakatau, Indonesia – 1883

22. Volcanoes and climate Modern examples
Mount St. Helens, Washington
El Chichón, Mexico
Mount Pinatubo, Phillippines

23. Pinatubo Eruption June 1991
Map showing areal distribution of pyroclastic flows of June 1991 and destructive lahars that ensued in September 1991, killing many more people than the eruption

24. Sulfer dioxide emissions of large volcanic eruptions from 1979-91, in thousands and millions of tons

25. Impact of SO2 emissions on global climate, caused by formation of H2SO4 aerosol, deflecting radiant energy from the Sun into the Stratosphere