Chapter 2 Final Notes

Question 1

• Divergent boundaries: Continental rifts and Mid-ocean ridges
o Know the igneous rocks, type of melting, type of metamorphism, style of deformation, all characteristics of the boundaries! Could you draw a cross-section? What are the special features of these plate boundaries (e.g. a mid-ocean ridge is where new crust forms)

Answer 1

• Spreading boundary, plates pull apart.
• New oceanic crust solidifies from basaltic magma along the ridge axis. As plates move away from the axis, they cool, and the lithospheric mantle forms and thickens
• Divergent boundaries: Continental rifts (two continental plates) and Mid-ocean ridges (two oceanic plates).
• Normal faults (dip slip faults) form at divergent boundaries. Volcanoes, rifting, are found here in both.
• Igneous rocks - both mafic gabbros (intrusive) and basalts (extrusive).
▪ Melting - Decompression
▪ Metamorphism - Hydrothermal and Contact MM.
▪ Faults and stresses - Normal faults, tensile stresses
▪ Deformation -
▪ Special features - MORs create oceanic crust. Continental rifts thick sedimentary basins, which are useful for making oil and coal.

Question 2

• Convergent boundaries: Continent-Continent collision, Subduction zones
o Know the igneous rocks, type of melting, type of metamorphism, style of deformation, all characteristics of the boundaries! Could you draw a cross-section? What are the special features of these plate boundaries?

Answer 2

• Continent-Continent collision (two continental plates, mountains form). Subduction zones (two oceanic plates- Plates push into each other. Reverse/thrust faults (dip slip faults) form at convergent boundaries.
▪ Igneous rocks - Felsic granite, volcanic. Also, pyroclastics, such as ignimbrites and rhyolites

Question 3

• Transform boundaries:
o Know the igneous rocks, type of melting, type of metamorphism, style of deformation, all characteristics of the boundaries! Could you draw a cross-section? What are the special features of these plate boundaries?

Answer 3

• Slide past each other (map view). Strike-slip faults form. Usually occur with divergent/convergent boundaries.
▪ Igneous rocks - NONE. No volcanism, so no igneous activity.
▪ Melting -
▪ Metamorphism -Metamorphism at depth.
▪ Faults and stresses - right/left lateral strike slip faults, shear stresses.
• Special features - Can cut MORs and continental crust (San Andreas).

Question 4

• Special plate locations: Hot-Spots

o What type of melting, what type of igneous rocks, what type of metamorphism?

Answer 4

• Hot-Spots are when a big magma chamber is right under tectonic plates. It melts the crust. The crust moves, causing volcanoes to form in a linear formation called a volcanic arc chain, such as Hawaii.
• They will be extrusive rocks. At MORs, they are mafic basalts. In subduction zones, they are felsic because when the magma goes up the crust it brings along the silica in the crust with it.