Week 5 - Tectonics

You should totally listen to this whilst reading the blog, it's in no way a shameful plug of my own band... 


Week 5 - After what seems like months trawling through endless sheets of data about Belfast and learning obscure geography terminology which I'm not sure if I'll ever use again it's finally over and we get to start one of my favourite modules. Tectonics.


Now tectonics isn't one of my favourite modules only because it has a t-rex but also because it produces such amazing things like this and continuously amazes people worldwide. It's unlikely that we will ever understand everything there is to know about tectonics and that's what makes it so interesting.


Right so, where did we leave off? I know many people are probably thinking that, not able to remember much about tectonics. Vicky's already so elegantly gone through what we did during the week involving volcanoes so I'll reintroduce you to the tectonics module from the start...


The year started off with us having to do that lovely essay... remember that one? It was all about the history of plate tectonics. The Wilson Cycle, similar fossils found on different sides of the world etc.
Next came the different types of plate boundaries and seeing as I'm a nice person (most of the time) I'll summarise them for you:


Conservative Boundaries: e.g the San Andreas Fault Line


There is no subduction or adduction, the plates try to move laterally against each other instead. No volcanoes occur here but instead there are massive earthquakes

Hotspots: e.g. Iceland, Hawaii (shows plate moving NW) and Yellowstone (biggest and highest risk) 


Not really a boundary type, rather a surface representation of a mantle plume, causes the production of a chain of islands, can result in massive volcanoes e.g. Yellowstone and Iceland




Divergent: e.g. Iceland (Mid-Atlantic Ridge), the East African Ridge

This diagram probably explains it best. There's only one example of a divergent plate boundary not in the middle of a plate and that's Iceland. It begins with an upwelling of magma in a plume driven by thermonuclear decay in the core, this causes a bulge in land mass. The plume then rises and starts a convection current at the base of the Lithosphere which begins the spreading of the Lithosphere and causes the thinning of the lithosphere. The thinning causes the creation of the valley, lakes form in these. Once the lithosphere becomes thin enough volcanoes form and then a rift, once a rift reaches the ocean it will flood separating the plate. 


Convergent: The writing should be next to the correct diagram, it isn't... my bad? 

Oceanic - Oceanic: e.g. Japan is a mature Island Arc, Aleutian Islands
1. Subduction produces partial melting and the formation of a chain of volcanoes. Produces an island arc. 
2. Build up of intrusive and extrusive igneous material, mixed with sediment forms larger Islands. 
3. The island chains join up and sediments form an accretionary wedge or prism which builds onto the fore arc area. 
4. Hazards - Volcanoes (variety of types), Earthquakes (very powerful) and Tidal Waves

Oceanic - Continental: e.g. Mt Saint Helens, Popcatepetl 

1. Weight of the continental sediments causes subsidence of the oceanic crust.
2. Subduction develops and an island arc forms
3. Compression from plate movement cause the crust to thicken and shorten through folding and thrust faulting. Fold mountain chain is formed e.g. the Andes. 
4. Hazards - Very explosive volcanoes e.g. MSH, Popocatepetl (Mexico City)

Continental - Continental: 

This is the mountain building process (known as Orogeny), the best case study for this are the Himalayas. During continental - continental collision neither plate is subducted instead they are either forced upwards or pushed sideways. 

Hazards = Earthquakes and huge potential for mass movement e.g. Lahars. There are no volcanoes because the crust is too thick.

I have explained this in a very hap-hazard way, for a decent description/explanation go here, they don't have awesome music though...