Structure of the Earth: Lithosphere - rigid, solid, rocky - makes the plates; vertical variations, crust, mantle; horizontal variations, continental crust - thick (32-40 km) and light, ocean crust - thin (7 km) and heavy; Asthenosphere - soft, partially melted

Plate Boundaries: divergent boundaries - mid-ocean ridges, basalt volcs; create ocean crust, convergent boundaries, subduction zones, at least one ocean plate, explosive volcs., destroy ocean crust; mountain building, two continents; transform boundaries

Divergent Boundaries: motion: away from each other; creates ocean crust; gentle lava volcanos; small shallow earthquakes; mid-ocean ridge; Iceland, Mid-Atlantic Ridge

Convergent Boundaries: subduction zone: motion - toward each other, ocean crust goes down under other plate; destroys ocean crust; explosive, deadly volcanoes; huge, deep earthquakes; trench and volcanic arc; arc-trench gap, Cascades, Japan, Andes, Philippines, Aleutians; continental collision: motion - toward each other; no effect on ocean crust; no volcanoes; variable earthquakes; huge mountains; Himalayas, Alps, Appalachians

Transform: side-by-side sliding motion; no effect on ocean crust; no volcanoes; variable earthquakes; subtle landforms; San Andreas

Compare and contrast Lithosphere and Asthenosphere. Explain the vertical and horizontal variations within the Lithosphere. How do the horizontal variations affect plate tectonics?

Describe the three basic types of plate boundaries in terms of: relative direction of plate motions, effect on ocean crust, type of volcanism, type of earthquakes, landforms, and give an example of a place where it is present today.

Describe the relationship between angle of subduction and the width of the arc-trench gap. Be able to determine the relative steepness of subduction angles from a map.