bibliography
http://en.wikipedia.org/ - Wikipedia
https://www.google.com/imghp?hl=en&tab=ii&authuser=0 - Google Images
http://www.kidsgeo.com/index.php - Geography & Geology For Kids, The Study Of Earth
http://earthquake.usgs.gov/research/structure/crust/index.php - Earthquakes Hazards Program/How Thick Is Earth's Crust
http://www.geography4kids.com/index.html - Geography 4 Kids
http://earth.rice.edu/mtpe/geo/geosphere.html
http://earth.rice.edu/mtpe/hydro/hydrosphere.html - earth.rice.edu
http://earth.rice.edu/mtpe/atmo/atmosphere.html
http://www.windows2universe.org/earth/interior/plate_tectonics.html - Windows 2 Universe