chapter 7 plate tectonics

Question 1

tillites

Answer 1

ancient glacial deposits preserved within a rock sequence.

Question 2

evaporites

Answer 2

minerals formed by the evaporation of hypersaline water. e.g. halite/gypsum/anhydrite

Question 3

apparent polar wandering curve

Answer 3

a line on a map which joins up the apparent positions of the magnetic north pole over time.

Question 4

orogeny

Answer 4

a period of mountain building.

Question 5

transform fault

Answer 5

a strike-slip fault which: ends at the junction of another plate boundary or fault; shows the same amount of deformation across the fault zone; can form a tectonic plate boundary.

Question 6

tear fault

Answer 6

a strike-slip fault which: dies out without a junction with another fault; has more displacement in the middle of the fault zone; cannot form a tectonic plate boundary.

Question 7

transform plate boundary

Answer 7

a fault where no crust is created or destroyed.

Question 8

sheeted dykes

Answer 8

form from magma which usually does not reach the surface, and usually composed of dolerite.

Question 9

pillow lava

Answer 9

form when lava erupts underwater, and cools rapidly in cold sea water, usually composed of basalt. The rounded masses formed are called pillows.

Question 10

island arc

Answer 10

a curved line of andesitic volcanic islands. as the subducting plate heats up, partial melting occurs along the top surface of the descending oceanic crust, producing basaltic magma. As this wet, less dense, hot magma rises it may melt and differentiate into intermediate, andesite lavas.

Question 11

deep-ocean trench

Answer 11

a long, narrow, linear submarine depression with relatively steep sides; the deepest example is over 10km deep. Trenches occur alongside island arcs or fold mountain belts and indicate where a plate is beginning to descend along a subduction zone.