Tips for Drawing Cross Sections Identify plate boundaries on the map – these may be divergent boundaries characterized by mid-ocean ridges or convergent boundaries characterized by a trench and either a volcanic island arc or continental volcanic arc o Mid-ocean ridges are LONG and mostly continuous except where they are broken by transverse faults o Straight lines on a map unbroken by transverse faults and without obvious ridges may be sonar tracks from ships; it’s ok to ask for clarification with these o Don’t confuse seamounts and ridges produced by hotspot activity with mid-ocean ridges. Remember – mid-ocean ridges are basically continuous except for transverse faults o Don’t confuse trenches with continental slopes. Continental slopes may look dark by contrast with the continental shelf but a trench will be very dark, significantly darker than the abyssal plain. Trenches will also be bordered by either volcanic islands or continental volcanoes. Determine if continental margins are active or passive - is there a plate boundary adjacent to the continent or are any plate boundaries on the map a long way away? Make sure that parts of your diagram which should break the surface of the ocean (e.g. islands, continents) actually break the surface and that parts that shouldn’t break the surface (e.g. mid-ocean ridges) don’t break the surface. Make sure you draw your layers with appropriate thickness o Ocean crust should be thin, continental crust should be thick o If a transect crosses an island followed by shallow ocean followed by more land, that shallow ocean is probably a continental shelf and therefore sits on continental crust o At divergent boundaries, the ocean crust and lithosphere should taper right up to the peak of the mid-ocean ridge to show the asthenosphere reaching up right to the peak of the ridge Make sure to label all layers and appropriate features o For a passive margin, this includes continental shelf (which sits on continental crust), continental slope, continental rise (boundary between continental and oceanic crust occurs underneath the continental slope and rise), and abyssal plain o For an active margin/convergent boundary, this includes a trench and a continental volcanic arc or volcanic island arc o For a divergent boundary, this is the mid-ocean ridge o Don’t forget to label crust, lithosphere, asthenosphere Make sure to answer any other parts of the question! .