The earth’s “crust” refers to the layer of rock which surrounds our planet’s mantle and core. Its thickness ranges from approximately 5 to 8 miles. The eight most common elements in the earth's crust are listed in this table:
| Element |
Portion of Crust |
| Oxygen |
0.4660 |
| Magnesium |
0.0209 |
| Iron |
0.0500 |
| Silicon |
0.2772 |
| Aluminum |
0.0813 |
| Potassium |
0.0259 |
| Sodium |
0.0283 |
| Calcium |
0.0363 |
Order these elements in the earth's crust from most abundant to least abundant. Estimate how much the earth's crust is made up of the three most abundant elements.