 What I want to talk about is mantle plumes and how they relate to flood basalts and chains of ocean islands But before I can do that I need to talk a little bit about viscosity for those of you who haven't come across this term a high Viscosity fluid is a fluid that doesn't flow very well and a good example of that is honey a Low viscosity fluid is a fluid that flows easily and water is a well-known example If you put honey in the fridge it becomes very viscous Whereas if you take it out and heat it it becomes very low viscosity or viscosity decreases And this is important because temperature has a very very profound influence on Viscosity and that's true of honey. It's also true of the mantle and it very much affects the way the mantle behaves and the way it and It also affects how mantle plumes behave mantle plumes are responsible for flood basalts and a very good example Of a flood basalt is the Deccan Traps and this third for this first slide shows a picture of the Deccan Traps And you can see flow after flow You can see them in the foreground in the middle ground and in the distance and these Flows with almost nothing in between Over a thousand meters thick and they extend over an area of about two thousand by two thousand kilometers There are a number of flood basalts known in the geological history. They occur about once every 10 to 20 million years Another good example is the Siberian Traps Which is obviously in Siberia and they are responsible for the biggest mass extinction in the geological record The second biggest mass extinction Occurs 65 million years ago in association with the eruption of the Deccan Traps And it was responsible for the demise of the dinosaurs. So what are mantle plumes and how do they work? This is India 65 million years ago when the Deccan Traps erupted the red spot Shows where the center of the Deccan Traps plume was The Deccan Traps are in India and part of the Deccan Traps plume out there is the Sashal Islands Which are currently not part of India, but were at the time that the Deccan Traps erupted This is what the Deccan Traps looks like today. The current position of the hotspot is at Reunion Island Notice that the Sashals are no longer connected to India. They've been separated from India Sometime after the Deccan Traps why a spreading center shown here Notice that there's a chain of chain of volcanoes extending from Reunion to the Sashals and From below the Deccan Traps towards the spreading center. It's not Reunion that is moved. It is the it is the Sashals and the traps that are moved The the the Reunion plume or the Deccan Traps plume has remained Stationary and it's plate tectonics that have moved The Deccan Traps away from the Sashals and both the Sashals and the Deccan Traps away from Reunion Island