Module 2 - plate tectonics

Question 1

What is the jigsaw fit?

Answer 1

-The theory of jigsaw fit is the idea that if you were to slide the continents toward each other they would almost make a perfect
jigsaw fit.
-This theory supports that our continents were once all joined as a
supercontinent called Pangaea.
-Alfred Wegener used the jigsaw fit to theorise the continental drift

Question 2

What is the theory of the sea floor spreading?

Answer 2

-In the 1960s it became possible to map the seafloor with sonar, Harry Hess noticed while in WWll the relationship between the mid-Atlantic Ridge system and oceanic trenches. Using Holmes theory he proposed that the sea floor was spreading.

Question 3

what are the types of tectonic plate boundaries?

Answer 3

-A divergent boundary occurs when two tectonic plates move away from each other. an example is a mid-ocean ridge.
-A convergent boundary is when two plates come together, The impact of the colliding plates can cause the edges of one or both plates to buckle up into mountain ranges or one of the plates may bend down into a deep seafloor trench. An example is the pacific ring of fire.
-Two plates sliding past each other form a transform plate boundary. Earthquakes are common along these faults. The crust is cracked and broken at transform margins, but is not created or destroyed. An example is the San Andreas fault zone

Question 4

What are the different types of faults?

Answer 4

Normal faults result from tensional forces when rocks are displaced away from each other.
Reverse faults results of compressional forces when rocks are displaced towards each other.
Transform faults results from either compressional or extensional forces when rocks slip parallel to each other.

Question 5

What are the different types of crust that create different boundaries

Answer 5

Divergent boundaries:
Oceanic-Oceanic -At divergent plate margins, plates are moving apart and a new lithosphere is being created.
Continental-Continental- At divergent plate margins, plates are moving apart. Within continents, divergent margins produce rift valleys
Convergent boundaries:
Oceanic - Oceanic -At convergent plate margins, plates are moving towards one another. A trench is created due to the subduction of the denser layer (the older one) and as the layer melts island arcs are created.
Oceanic-continental -At convergent plate margins, plates are moving towards one another. A trench is created as the oceanic crust subducts beneath the surface to melt and raise into a volcanic arc.
Continental-continental- At convergent plate margins, plates are
moving towards one another. Mountains are formed as the layers are pushed together. There is no subduction and as such not volcanic activity or deep focus earthquakes.