1. In your own words, describe what a hotspot is? Draw a picture to represent what a hotspot looks like below the surface? Give one example of a hotspot chain? DAILY WARM-UP

2. Hypothesized that Hotspots are Fed by Mantle Plumes W. Jason Morgan (1935-) In a 1972 publication, Jason Morgan described his new theory of deep mantle plumes.

3. MANTLE PLUME DEFINITION A mantle plume is a narrow region of mantle material that is hotter than the surrounding mantle. This allows the material to rise to the surface, to melt when it reaches the lithosphere, and then to erupt as an intra-plate volcano. Jason Morgan postulated that the hotspots described by Tuzo Wilson are the result of mantle plumes that originate deep within the mantle.

4. MANTLE PLUME DEFINITION Small Tails, Large Heads

5. MANTLE PLUME DEFINITION How can you See a Mantle Plume? A problem with the plume hypothesis: It is difficult to find evidence that plumes themselves exist … Can you look inside the Earth to see a plume?

6. MANTLE TOMOGRAPHY CATSCAN of the Human Brain A CAT scan is a computerized axial tomography scan. Tomography means imaging by section. X-rays are taken at various angles around a central axis of the organ of interest.

7. MANTLE TOMOGRAPHY CATSCAN of the Earth Scientists use seismic waves (like a doctor uses X-rays) to get a series of cross sections of the Earth’s mantle. Scientists record seismic waves from earthquakes that happen all the time (some earthquakes are too small for us to feel but scientists can still record the motion). Mantle tomography provides an image of the inside of the Earth based on these seismic waves. This is similar to a CAT scan which provide doctors with an image of the inside of a persons body or head.

8. In 2003 Montelli and others, claim to have used tomography to image mantle plumes for the first time below some major hotspot locations on planet Earth. DO WE SEE PLUMES?

9. MANTLE TOMOGRAPHY Can we see Plumes or Not? Some scientists argue that the tomography images show signals of plumes. BUT others don’t believe the tomography images provide convincing results. The scientific debate goes on...

10. MANTLE PLUME DEFINITION Compared to the Size of the Earth, Plumes are Small

11. MANTLE PLUME SKEPTICS Do Mantle Plumes Really Exist? If you can’t see them, does it mean plumes don’t exist? Mantle plumes likely exist, but we just don’t have the technology to properly view them... yet. Linear age progressive ocean islands chains do provide good evidence for mantle plumes.

12. MANTLE PLUME SKEPTICS Not Everyone Accepts Mantle Plume Theory There are skeptics of the mantle plume theory. They believe hotspot volcanoes form from other mid- plate processes and not from plumes.