2. Earth’s Crust OCEANIC CONTINENTAL
Denser, Basaltic, THINNER Mafic – rich in Iron (Fe) and Magnesium (Mg)
CONTINENTAL
Lighter, Granitic, THICKER Felsic – rich in Aluminum (Al) and Silicon (Si)
ESRT page 10

3. The Crust
The crust is composed of two rocks. The continental crust is mostly granite. The oceanic crust is basalt. Basalt is much denser than the granite. Because of this the less dense continents ride on the denser oceanic plates.

4. PLATE BOUNDARIES
ESRT Page 5

7. 1. DIVERGENT Plates move apart, magma rises up
New crust is formed, volcanoes
Results in
Mid-Ocean ridges and
Rift Valleys on continents

10. 2. Transform Plates slide past one another Results in - Faulting
- Ex. San Andreas Fault in California

12. 2. CONVERGENT plates converge (move together)
SUBDUCTION – more dense plate moves under less dense

13. a. Oceanic vs. Continental Crust (subduction)
Oceanic (more dense) plate subducts under continental (less dense) plate
Results in
- Trenches
- volcanic chain along coast of continent
EX. Andes Mountains along South America

20. b. 2 Oceanic Plates (subduction)
More dense plate subducts under the less dense oceanic plate
Results in
- Trenches, volcanoes and volcanic island chains
Ex. Aleutian Islands in Alaska

24. C. 2 Continental Plates (compression)
Plates collide
Rocks break and build up
Results In
- Mountain building
Ex. Himalayas

28. ESRT Page 5 2 CONVERGING PLATES
OVERRIDING PLATE
SUBDUCTING PLATE